tint: Preserve padding in matrices with three rows

The PreservePadding transform now decomposes writes to matrices with
three rows into separate column vector writes, to avoid modifying
padding between columns.

Bug: tint:1571
Change-Id: If575f79bb87f52810783fd3338e2f3ce3228ab2e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/121600
Auto-Submit: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: James Price <jrprice@google.com>

test/tint/buffer/uniform/std140/array/mat2x3_f16/to_storage.wgsl.expected.glsl

@@ -14,6 +14,20 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   f16mat2x3 inner[4];
 } s;
 
+void assign_and_preserve_padding_1_s_X(uint dest[1], f16mat2x3 value) {
+  s.inner[dest[0]][0] = value[0u];
+  s.inner[dest[0]][1] = value[1u];
+}
+
+void assign_and_preserve_padding_s(f16mat2x3 value[4]) {
+  {
+    for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+      uint tint_symbol[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+    }
+  }
+}
+
 f16mat2x3 conv_mat2x3_f16(mat2x3_f16 val) {
   return f16mat2x3(val.col0, val.col1);
 }
@@ -29,8 +43,9 @@ f16mat2x3[4] conv_arr4_mat2x3_f16(mat2x3_f16 val[4]) {
 }
 
 void f() {
-  s.inner = conv_arr4_mat2x3_f16(u.inner);
-  s.inner[1] = conv_mat2x3_f16(u.inner[2u]);
+  assign_and_preserve_padding_s(conv_arr4_mat2x3_f16(u.inner));
+  uint tint_symbol_1[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_1, conv_mat2x3_f16(u.inner[2u]));
   s.inner[1][0] = u.inner[0u].col1.zxy;
   s.inner[1][0].x = u.inner[0u].col1[0u];
 }

test/tint/buffer/uniform/std140/array/mat2x3_f16/to_storage.wgsl.expected.msl

@@ -14,9 +14,20 @@ struct tint_array {
     T elements[N];
 };
 
+void assign_and_preserve_padding_1(device half2x3* const dest, half2x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+}
+
+void assign_and_preserve_padding(device tint_array<half2x3, 4>* const dest, tint_array<half2x3, 4> value) {
+  for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+    assign_and_preserve_padding_1(&((*(dest))[i]), value[i]);
+  }
+}
+
 kernel void f(device tint_array<half2x3, 4>* tint_symbol [[buffer(1)]], const constant tint_array<half2x3, 4>* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
-  (*(tint_symbol))[1] = (*(tint_symbol_1))[2];
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
+  assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
   (*(tint_symbol))[1][0] = half3((*(tint_symbol_1))[0][1]).zxy;
   (*(tint_symbol))[1][0][0] = (*(tint_symbol_1))[0][1][0];
   return;

test/tint/buffer/uniform/std140/array/mat2x3_f16/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 89
+; Bound: 123
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
@@ -20,13 +20,20 @@
                OpName %u_block "u_block"
                OpMemberName %u_block 0 "inner"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest "dest"
+               OpName %value "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_0 "value"
+               OpName %i "i"
+               OpName %var_for_index "var_for_index"
                OpName %conv_mat2x3_f16 "conv_mat2x3_f16"
                OpName %val "val"
                OpName %conv_arr4_mat2x3_f16 "conv_arr4_mat2x3_f16"
                OpName %val_0 "val"
                OpName %arr "arr"
-               OpName %i "i"
-               OpName %var_for_index "var_for_index"
+               OpName %i_0 "i"
+               OpName %var_for_index_1 "var_for_index_1"
                OpName %f "f"
                OpDecorate %u_block_std140 Block
                OpMemberDecorate %u_block_std140 0 Offset 0
@@ -43,6 +50,7 @@
                OpDecorate %_arr_mat2v3half_uint_4 ArrayStride 16
                OpDecorate %s DescriptorSet 0
                OpDecorate %s Binding 1
+               OpDecorate %_arr_uint_uint_1 ArrayStride 4
        %half = OpTypeFloat 16
      %v3half = OpTypeVector %half 3
  %mat2x3_f16 = OpTypeStruct %v3half %v3half
@@ -57,98 +65,147 @@
     %u_block = OpTypeStruct %_arr_mat2v3half_uint_4
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
-         %15 = OpTypeFunction %mat2v3half %mat2x3_f16
-         %22 = OpTypeFunction %_arr_mat2v3half_uint_4 %_arr_mat2x3_f16_uint_4
-%_ptr_Function__arr_mat2v3half_uint_4 = OpTypePointer Function %_arr_mat2v3half_uint_4
-         %28 = OpConstantNull %_arr_mat2v3half_uint_4
-%_ptr_Function_uint = OpTypePointer Function %uint
-         %31 = OpConstantNull %uint
-       %bool = OpTypeBool
-%_ptr_Function__arr_mat2x3_f16_uint_4 = OpTypePointer Function %_arr_mat2x3_f16_uint_4
-         %44 = OpConstantNull %_arr_mat2x3_f16_uint_4
-%_ptr_Function_mat2v3half = OpTypePointer Function %mat2v3half
-%_ptr_Function_mat2x3_f16 = OpTypePointer Function %mat2x3_f16
-     %uint_1 = OpConstant %uint 1
        %void = OpTypeVoid
-         %57 = OpTypeFunction %void
+     %uint_1 = OpConstant %uint 1
+%_arr_uint_uint_1 = OpTypeArray %uint %uint_1
+         %15 = OpTypeFunction %void %_arr_uint_uint_1 %mat2v3half
      %uint_0 = OpConstant %uint 0
-%_ptr_StorageBuffer__arr_mat2v3half_uint_4 = OpTypePointer StorageBuffer %_arr_mat2v3half_uint_4
-%_ptr_Uniform__arr_mat2x3_f16_uint_4 = OpTypePointer Uniform %_arr_mat2x3_f16_uint_4
         %int = OpTypeInt 32 1
+         %25 = OpConstantNull %int
+%_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
+         %29 = OpConstantNull %uint
       %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_mat2v3half = OpTypePointer StorageBuffer %mat2v3half
+         %35 = OpTypeFunction %void %_arr_mat2v3half_uint_4
+%_ptr_Function_uint = OpTypePointer Function %uint
+       %bool = OpTypeBool
+%_ptr_Function__arr_mat2v3half_uint_4 = OpTypePointer Function %_arr_mat2v3half_uint_4
+         %53 = OpConstantNull %_arr_mat2v3half_uint_4
+%_ptr_Function_mat2v3half = OpTypePointer Function %mat2v3half
+         %63 = OpTypeFunction %mat2v3half %mat2x3_f16
+         %70 = OpTypeFunction %_arr_mat2v3half_uint_4 %_arr_mat2x3_f16_uint_4
+%_ptr_Function__arr_mat2x3_f16_uint_4 = OpTypePointer Function %_arr_mat2x3_f16_uint_4
+         %87 = OpConstantNull %_arr_mat2x3_f16_uint_4
+%_ptr_Function_mat2x3_f16 = OpTypePointer Function %mat2x3_f16
+         %98 = OpTypeFunction %void
+%_ptr_Uniform__arr_mat2x3_f16_uint_4 = OpTypePointer Uniform %_arr_mat2x3_f16_uint_4
+        %107 = OpConstantComposite %_arr_uint_uint_1 %uint_1
      %uint_2 = OpConstant %uint 2
 %_ptr_Uniform_mat2x3_f16 = OpTypePointer Uniform %mat2x3_f16
-         %77 = OpConstantNull %int
-%_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
 %_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
 %_ptr_StorageBuffer_half = OpTypePointer StorageBuffer %half
 %_ptr_Uniform_half = OpTypePointer Uniform %half
-%conv_mat2x3_f16 = OpFunction %mat2v3half None %15
-        %val = OpFunctionParameter %mat2x3_f16
-         %18 = OpLabel
-         %19 = OpCompositeExtract %v3half %val 0
-         %20 = OpCompositeExtract %v3half %val 1
-         %21 = OpCompositeConstruct %mat2v3half %19 %20
-               OpReturnValue %21
-               OpFunctionEnd
-%conv_arr4_mat2x3_f16 = OpFunction %_arr_mat2v3half_uint_4 None %22
-      %val_0 = OpFunctionParameter %_arr_mat2x3_f16_uint_4
-         %25 = OpLabel
-        %arr = OpVariable %_ptr_Function__arr_mat2v3half_uint_4 Function %28
-          %i = OpVariable %_ptr_Function_uint Function %31
-%var_for_index = OpVariable %_ptr_Function__arr_mat2x3_f16_uint_4 Function %44
-               OpBranch %32
-         %32 = OpLabel
-               OpLoopMerge %33 %34 None
-               OpBranch %35
-         %35 = OpLabel
-         %37 = OpLoad %uint %i
-         %38 = OpULessThan %bool %37 %uint_4
-         %36 = OpLogicalNot %bool %38
-               OpSelectionMerge %40 None
-               OpBranchConditional %36 %41 %40
-         %41 = OpLabel
-               OpBranch %33
-         %40 = OpLabel
-               OpStore %var_for_index %val_0
-         %45 = OpLoad %uint %i
-         %47 = OpAccessChain %_ptr_Function_mat2v3half %arr %45
-         %49 = OpLoad %uint %i
-         %51 = OpAccessChain %_ptr_Function_mat2x3_f16 %var_for_index %49
-         %52 = OpLoad %mat2x3_f16 %51
-         %48 = OpFunctionCall %mat2v3half %conv_mat2x3_f16 %52
-               OpStore %47 %48
-               OpBranch %34
-         %34 = OpLabel
-         %53 = OpLoad %uint %i
-         %55 = OpIAdd %uint %53 %uint_1
-               OpStore %i %55
-               OpBranch %32
-         %33 = OpLabel
-         %56 = OpLoad %_arr_mat2v3half_uint_4 %arr
-               OpReturnValue %56
-               OpFunctionEnd
-          %f = OpFunction %void None %57
-         %60 = OpLabel
-         %63 = OpAccessChain %_ptr_StorageBuffer__arr_mat2v3half_uint_4 %s %uint_0
-         %66 = OpAccessChain %_ptr_Uniform__arr_mat2x3_f16_uint_4 %u %uint_0
-         %67 = OpLoad %_arr_mat2x3_f16_uint_4 %66
-         %64 = OpFunctionCall %_arr_mat2v3half_uint_4 %conv_arr4_mat2x3_f16 %67
-               OpStore %63 %64
-         %71 = OpAccessChain %_ptr_StorageBuffer_mat2v3half %s %uint_0 %int_1
-         %75 = OpAccessChain %_ptr_Uniform_mat2x3_f16 %u %uint_0 %uint_2
-         %76 = OpLoad %mat2x3_f16 %75
-         %72 = OpFunctionCall %mat2v3half %conv_mat2x3_f16 %76
-               OpStore %71 %72
-         %79 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %77
-         %81 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %31 %uint_1
-         %82 = OpLoad %v3half %81
-         %83 = OpVectorShuffle %v3half %82 %82 2 0 1
-               OpStore %79 %83
-         %85 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %int_1 %77 %uint_0
-         %87 = OpAccessChain %_ptr_Uniform_half %u %uint_0 %31 %uint_1 %31
-         %88 = OpLoad %half %87
-               OpStore %85 %88
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %15
+       %dest = OpFunctionParameter %_arr_uint_uint_1
+      %value = OpFunctionParameter %mat2v3half
+         %22 = OpLabel
+         %26 = OpCompositeExtract %uint %dest 0
+         %28 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %26 %25
+         %30 = OpCompositeExtract %v3half %value 0
+               OpStore %28 %30
+         %31 = OpCompositeExtract %uint %dest 0
+         %33 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %31 %int_1
+         %34 = OpCompositeExtract %v3half %value 1
+               OpStore %33 %34
+               OpReturn
+               OpFunctionEnd
+%assign_and_preserve_padding_s = OpFunction %void None %35
+    %value_0 = OpFunctionParameter %_arr_mat2v3half_uint_4
+         %38 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %29
+%var_for_index = OpVariable %_ptr_Function__arr_mat2v3half_uint_4 Function %53
+               OpStore %i %29
+               OpBranch %41
+         %41 = OpLabel
+               OpLoopMerge %42 %43 None
+               OpBranch %44
+         %44 = OpLabel
+         %46 = OpLoad %uint %i
+         %47 = OpULessThan %bool %46 %uint_4
+         %45 = OpLogicalNot %bool %47
+               OpSelectionMerge %49 None
+               OpBranchConditional %45 %50 %49
+         %50 = OpLabel
+               OpBranch %42
+         %49 = OpLabel
+               OpStore %var_for_index %value_0
+         %55 = OpLoad %uint %i
+         %56 = OpCompositeConstruct %_arr_uint_uint_1 %55
+         %57 = OpLoad %uint %i
+         %59 = OpAccessChain %_ptr_Function_mat2v3half %var_for_index %57
+         %60 = OpLoad %mat2v3half %59
+         %54 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %56 %60
+               OpBranch %43
+         %43 = OpLabel
+         %61 = OpLoad %uint %i
+         %62 = OpIAdd %uint %61 %uint_1
+               OpStore %i %62
+               OpBranch %41
+         %42 = OpLabel
+               OpReturn
+               OpFunctionEnd
+%conv_mat2x3_f16 = OpFunction %mat2v3half None %63
+        %val = OpFunctionParameter %mat2x3_f16
+         %66 = OpLabel
+         %67 = OpCompositeExtract %v3half %val 0
+         %68 = OpCompositeExtract %v3half %val 1
+         %69 = OpCompositeConstruct %mat2v3half %67 %68
+               OpReturnValue %69
+               OpFunctionEnd
+%conv_arr4_mat2x3_f16 = OpFunction %_arr_mat2v3half_uint_4 None %70
+      %val_0 = OpFunctionParameter %_arr_mat2x3_f16_uint_4
+         %73 = OpLabel
+        %arr = OpVariable %_ptr_Function__arr_mat2v3half_uint_4 Function %53
+        %i_0 = OpVariable %_ptr_Function_uint Function %29
+%var_for_index_1 = OpVariable %_ptr_Function__arr_mat2x3_f16_uint_4 Function %87
+               OpBranch %76
+         %76 = OpLabel
+               OpLoopMerge %77 %78 None
+               OpBranch %79
+         %79 = OpLabel
+         %81 = OpLoad %uint %i_0
+         %82 = OpULessThan %bool %81 %uint_4
+         %80 = OpLogicalNot %bool %82
+               OpSelectionMerge %83 None
+               OpBranchConditional %80 %84 %83
+         %84 = OpLabel
+               OpBranch %77
+         %83 = OpLabel
+               OpStore %var_for_index_1 %val_0
+         %88 = OpLoad %uint %i_0
+         %89 = OpAccessChain %_ptr_Function_mat2v3half %arr %88
+         %91 = OpLoad %uint %i_0
+         %93 = OpAccessChain %_ptr_Function_mat2x3_f16 %var_for_index_1 %91
+         %94 = OpLoad %mat2x3_f16 %93
+         %90 = OpFunctionCall %mat2v3half %conv_mat2x3_f16 %94
+               OpStore %89 %90
+               OpBranch %78
+         %78 = OpLabel
+         %95 = OpLoad %uint %i_0
+         %96 = OpIAdd %uint %95 %uint_1
+               OpStore %i_0 %96
+               OpBranch %76
+         %77 = OpLabel
+         %97 = OpLoad %_arr_mat2v3half_uint_4 %arr
+               OpReturnValue %97
+               OpFunctionEnd
+          %f = OpFunction %void None %98
+        %100 = OpLabel
+        %104 = OpAccessChain %_ptr_Uniform__arr_mat2x3_f16_uint_4 %u %uint_0
+        %105 = OpLoad %_arr_mat2x3_f16_uint_4 %104
+        %102 = OpFunctionCall %_arr_mat2v3half_uint_4 %conv_arr4_mat2x3_f16 %105
+        %101 = OpFunctionCall %void %assign_and_preserve_padding_s %102
+        %111 = OpAccessChain %_ptr_Uniform_mat2x3_f16 %u %uint_0 %uint_2
+        %112 = OpLoad %mat2x3_f16 %111
+        %108 = OpFunctionCall %mat2v3half %conv_mat2x3_f16 %112
+        %106 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %107 %108
+        %113 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %25
+        %115 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %29 %uint_1
+        %116 = OpLoad %v3half %115
+        %117 = OpVectorShuffle %v3half %116 %116 2 0 1
+               OpStore %113 %117
+        %119 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %int_1 %25 %uint_0
+        %121 = OpAccessChain %_ptr_Uniform_half %u %uint_0 %29 %uint_1 %29
+        %122 = OpLoad %half %121
+               OpStore %119 %122
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/array/mat2x3_f32/to_storage.wgsl.expected.glsl

@@ -8,9 +8,24 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   mat2x3 inner[4];
 } s;
 
+void assign_and_preserve_padding_1_s_X(uint dest[1], mat2x3 value) {
+  s.inner[dest[0]][0] = value[0u];
+  s.inner[dest[0]][1] = value[1u];
+}
+
+void assign_and_preserve_padding_s(mat2x3 value[4]) {
+  {
+    for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+      uint tint_symbol[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+    }
+  }
+}
+
 void f() {
-  s.inner = u.inner;
-  s.inner[1] = u.inner[2];
+  assign_and_preserve_padding_s(u.inner);
+  uint tint_symbol_1[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_1, u.inner[2]);
   s.inner[1][0] = u.inner[0][1].zxy;
   s.inner[1][0].x = u.inner[0][1].x;
 }

test/tint/buffer/uniform/std140/array/mat2x3_f32/to_storage.wgsl.expected.msl

@@ -14,9 +14,20 @@ struct tint_array {
     T elements[N];
 };
 
+void assign_and_preserve_padding_1(device float2x3* const dest, float2x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+}
+
+void assign_and_preserve_padding(device tint_array<float2x3, 4>* const dest, tint_array<float2x3, 4> value) {
+  for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+    assign_and_preserve_padding_1(&((*(dest))[i]), value[i]);
+  }
+}
+
 kernel void f(device tint_array<float2x3, 4>* tint_symbol [[buffer(1)]], const constant tint_array<float2x3, 4>* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
-  (*(tint_symbol))[1] = (*(tint_symbol_1))[2];
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
+  assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
   (*(tint_symbol))[1][0] = float3((*(tint_symbol_1))[0][1]).zxy;
   (*(tint_symbol))[1][0][0] = (*(tint_symbol_1))[0][1][0];
   return;

test/tint/buffer/uniform/std140/array/mat2x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 42
+; Bound: 83
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -11,6 +11,13 @@
                OpMemberName %u_block 0 "inner"
                OpName %u "u"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest "dest"
+               OpName %value "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_0 "value"
+               OpName %i "i"
+               OpName %var_for_index "var_for_index"
                OpName %f "f"
                OpDecorate %u_block Block
                OpMemberDecorate %u_block 0 Offset 0
@@ -22,6 +29,7 @@
                OpDecorate %u Binding 0
                OpDecorate %s DescriptorSet 0
                OpDecorate %s Binding 1
+               OpDecorate %_arr_uint_uint_1 ArrayStride 4
       %float = OpTypeFloat 32
     %v3float = OpTypeVector %float 3
 %mat2v3float = OpTypeMatrix %v3float 2
@@ -34,38 +42,94 @@
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
        %void = OpTypeVoid
-         %12 = OpTypeFunction %void
+     %uint_1 = OpConstant %uint 1
+%_arr_uint_uint_1 = OpTypeArray %uint %uint_1
+         %12 = OpTypeFunction %void %_arr_uint_uint_1 %mat2v3float
      %uint_0 = OpConstant %uint 0
-%_ptr_StorageBuffer__arr_mat2v3float_uint_4 = OpTypePointer StorageBuffer %_arr_mat2v3float_uint_4
-%_ptr_Uniform__arr_mat2v3float_uint_4 = OpTypePointer Uniform %_arr_mat2v3float_uint_4
         %int = OpTypeInt 32 1
+         %22 = OpConstantNull %int
+%_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
+         %26 = OpConstantNull %uint
       %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_mat2v3float = OpTypePointer StorageBuffer %mat2v3float
+         %32 = OpTypeFunction %void %_arr_mat2v3float_uint_4
+%_ptr_Function_uint = OpTypePointer Function %uint
+       %bool = OpTypeBool
+%_ptr_Function__arr_mat2v3float_uint_4 = OpTypePointer Function %_arr_mat2v3float_uint_4
+         %50 = OpConstantNull %_arr_mat2v3float_uint_4
+%_ptr_Function_mat2v3float = OpTypePointer Function %mat2v3float
+         %60 = OpTypeFunction %void
+%_ptr_Uniform__arr_mat2v3float_uint_4 = OpTypePointer Uniform %_arr_mat2v3float_uint_4
+         %68 = OpConstantComposite %_arr_uint_uint_1 %uint_1
       %int_2 = OpConstant %int 2
 %_ptr_Uniform_mat2v3float = OpTypePointer Uniform %mat2v3float
-         %30 = OpConstantNull %int
-%_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
 %_ptr_StorageBuffer_float = OpTypePointer StorageBuffer %float
 %_ptr_Uniform_float = OpTypePointer Uniform %float
-          %f = OpFunction %void None %12
-         %15 = OpLabel
-         %18 = OpAccessChain %_ptr_StorageBuffer__arr_mat2v3float_uint_4 %s %uint_0
-         %20 = OpAccessChain %_ptr_Uniform__arr_mat2v3float_uint_4 %u %uint_0
-         %21 = OpLoad %_arr_mat2v3float_uint_4 %20
-               OpStore %18 %21
-         %25 = OpAccessChain %_ptr_StorageBuffer_mat2v3float %s %uint_0 %int_1
-         %28 = OpAccessChain %_ptr_Uniform_mat2v3float %u %uint_0 %int_2
-         %29 = OpLoad %mat2v3float %28
-               OpStore %25 %29
-         %32 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %30
-         %34 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %30 %int_1
-         %35 = OpLoad %v3float %34
-         %36 = OpVectorShuffle %v3float %35 %35 2 0 1
-               OpStore %32 %36
-         %38 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %int_1 %30 %uint_0
-         %40 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %30 %int_1 %uint_0
-         %41 = OpLoad %float %40
-               OpStore %38 %41
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %12
+       %dest = OpFunctionParameter %_arr_uint_uint_1
+      %value = OpFunctionParameter %mat2v3float
+         %19 = OpLabel
+         %23 = OpCompositeExtract %uint %dest 0
+         %25 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %23 %22
+         %27 = OpCompositeExtract %v3float %value 0
+               OpStore %25 %27
+         %28 = OpCompositeExtract %uint %dest 0
+         %30 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %28 %int_1
+         %31 = OpCompositeExtract %v3float %value 1
+               OpStore %30 %31
+               OpReturn
+               OpFunctionEnd
+%assign_and_preserve_padding_s = OpFunction %void None %32
+    %value_0 = OpFunctionParameter %_arr_mat2v3float_uint_4
+         %35 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %26
+%var_for_index = OpVariable %_ptr_Function__arr_mat2v3float_uint_4 Function %50
+               OpStore %i %26
+               OpBranch %38
+         %38 = OpLabel
+               OpLoopMerge %39 %40 None
+               OpBranch %41
+         %41 = OpLabel
+         %43 = OpLoad %uint %i
+         %44 = OpULessThan %bool %43 %uint_4
+         %42 = OpLogicalNot %bool %44
+               OpSelectionMerge %46 None
+               OpBranchConditional %42 %47 %46
+         %47 = OpLabel
+               OpBranch %39
+         %46 = OpLabel
+               OpStore %var_for_index %value_0
+         %52 = OpLoad %uint %i
+         %53 = OpCompositeConstruct %_arr_uint_uint_1 %52
+         %54 = OpLoad %uint %i
+         %56 = OpAccessChain %_ptr_Function_mat2v3float %var_for_index %54
+         %57 = OpLoad %mat2v3float %56
+         %51 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %53 %57
+               OpBranch %40
+         %40 = OpLabel
+         %58 = OpLoad %uint %i
+         %59 = OpIAdd %uint %58 %uint_1
+               OpStore %i %59
+               OpBranch %38
+         %39 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %60
+         %62 = OpLabel
+         %65 = OpAccessChain %_ptr_Uniform__arr_mat2v3float_uint_4 %u %uint_0
+         %66 = OpLoad %_arr_mat2v3float_uint_4 %65
+         %63 = OpFunctionCall %void %assign_and_preserve_padding_s %66
+         %71 = OpAccessChain %_ptr_Uniform_mat2v3float %u %uint_0 %int_2
+         %72 = OpLoad %mat2v3float %71
+         %67 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %68 %72
+         %73 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %22
+         %75 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %22 %int_1
+         %76 = OpLoad %v3float %75
+         %77 = OpVectorShuffle %v3float %76 %76 2 0 1
+               OpStore %73 %77
+         %79 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %int_1 %22 %uint_0
+         %81 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %22 %int_1 %uint_0
+         %82 = OpLoad %float %81
+               OpStore %79 %82
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/array/mat3x3_f32/to_storage.wgsl.expected.glsl

@@ -8,9 +8,25 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   mat3 inner[4];
 } s;
 
+void assign_and_preserve_padding_1_s_X(uint dest[1], mat3 value) {
+  s.inner[dest[0]][0] = value[0u];
+  s.inner[dest[0]][1] = value[1u];
+  s.inner[dest[0]][2] = value[2u];
+}
+
+void assign_and_preserve_padding_s(mat3 value[4]) {
+  {
+    for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+      uint tint_symbol[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+    }
+  }
+}
+
 void f() {
-  s.inner = u.inner;
-  s.inner[1] = u.inner[2];
+  assign_and_preserve_padding_s(u.inner);
+  uint tint_symbol_1[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_1, u.inner[2]);
   s.inner[1][0] = u.inner[0][1].zxy;
   s.inner[1][0].x = u.inner[0][1].x;
 }

test/tint/buffer/uniform/std140/array/mat3x3_f32/to_storage.wgsl.expected.msl

@@ -14,9 +14,21 @@ struct tint_array {
     T elements[N];
 };
 
+void assign_and_preserve_padding_1(device float3x3* const dest, float3x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+}
+
+void assign_and_preserve_padding(device tint_array<float3x3, 4>* const dest, tint_array<float3x3, 4> value) {
+  for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+    assign_and_preserve_padding_1(&((*(dest))[i]), value[i]);
+  }
+}
+
 kernel void f(device tint_array<float3x3, 4>* tint_symbol [[buffer(1)]], const constant tint_array<float3x3, 4>* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
-  (*(tint_symbol))[1] = (*(tint_symbol_1))[2];
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
+  assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
   (*(tint_symbol))[1][0] = float3((*(tint_symbol_1))[0][1]).zxy;
   (*(tint_symbol))[1][0][0] = (*(tint_symbol_1))[0][1][0];
   return;

test/tint/buffer/uniform/std140/array/mat3x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 42
+; Bound: 87
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -11,6 +11,13 @@
                OpMemberName %u_block 0 "inner"
                OpName %u "u"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest "dest"
+               OpName %value "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_0 "value"
+               OpName %i "i"
+               OpName %var_for_index "var_for_index"
                OpName %f "f"
                OpDecorate %u_block Block
                OpMemberDecorate %u_block 0 Offset 0
@@ -22,6 +29,7 @@
                OpDecorate %u Binding 0
                OpDecorate %s DescriptorSet 0
                OpDecorate %s Binding 1
+               OpDecorate %_arr_uint_uint_1 ArrayStride 4
       %float = OpTypeFloat 32
     %v3float = OpTypeVector %float 3
 %mat3v3float = OpTypeMatrix %v3float 3
@@ -34,38 +42,99 @@
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
        %void = OpTypeVoid
-         %12 = OpTypeFunction %void
+     %uint_1 = OpConstant %uint 1
+%_arr_uint_uint_1 = OpTypeArray %uint %uint_1
+         %12 = OpTypeFunction %void %_arr_uint_uint_1 %mat3v3float
      %uint_0 = OpConstant %uint 0
-%_ptr_StorageBuffer__arr_mat3v3float_uint_4 = OpTypePointer StorageBuffer %_arr_mat3v3float_uint_4
-%_ptr_Uniform__arr_mat3v3float_uint_4 = OpTypePointer Uniform %_arr_mat3v3float_uint_4
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_mat3v3float = OpTypePointer StorageBuffer %mat3v3float
-      %int_2 = OpConstant %int 2
-%_ptr_Uniform_mat3v3float = OpTypePointer Uniform %mat3v3float
-         %30 = OpConstantNull %int
+         %22 = OpConstantNull %int
 %_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
+         %26 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+      %int_2 = OpConstant %int 2
+     %uint_2 = OpConstant %uint 2
+         %37 = OpTypeFunction %void %_arr_mat3v3float_uint_4
+%_ptr_Function_uint = OpTypePointer Function %uint
+       %bool = OpTypeBool
+%_ptr_Function__arr_mat3v3float_uint_4 = OpTypePointer Function %_arr_mat3v3float_uint_4
+         %55 = OpConstantNull %_arr_mat3v3float_uint_4
+%_ptr_Function_mat3v3float = OpTypePointer Function %mat3v3float
+         %65 = OpTypeFunction %void
+%_ptr_Uniform__arr_mat3v3float_uint_4 = OpTypePointer Uniform %_arr_mat3v3float_uint_4
+         %73 = OpConstantComposite %_arr_uint_uint_1 %uint_1
+%_ptr_Uniform_mat3v3float = OpTypePointer Uniform %mat3v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
 %_ptr_StorageBuffer_float = OpTypePointer StorageBuffer %float
 %_ptr_Uniform_float = OpTypePointer Uniform %float
-          %f = OpFunction %void None %12
-         %15 = OpLabel
-         %18 = OpAccessChain %_ptr_StorageBuffer__arr_mat3v3float_uint_4 %s %uint_0
-         %20 = OpAccessChain %_ptr_Uniform__arr_mat3v3float_uint_4 %u %uint_0
-         %21 = OpLoad %_arr_mat3v3float_uint_4 %20
-               OpStore %18 %21
-         %25 = OpAccessChain %_ptr_StorageBuffer_mat3v3float %s %uint_0 %int_1
-         %28 = OpAccessChain %_ptr_Uniform_mat3v3float %u %uint_0 %int_2
-         %29 = OpLoad %mat3v3float %28
-               OpStore %25 %29
-         %32 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %30
-         %34 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %30 %int_1
-         %35 = OpLoad %v3float %34
-         %36 = OpVectorShuffle %v3float %35 %35 2 0 1
-               OpStore %32 %36
-         %38 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %int_1 %30 %uint_0
-         %40 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %30 %int_1 %uint_0
-         %41 = OpLoad %float %40
-               OpStore %38 %41
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %12
+       %dest = OpFunctionParameter %_arr_uint_uint_1
+      %value = OpFunctionParameter %mat3v3float
+         %19 = OpLabel
+         %23 = OpCompositeExtract %uint %dest 0
+         %25 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %23 %22
+         %27 = OpCompositeExtract %v3float %value 0
+               OpStore %25 %27
+         %28 = OpCompositeExtract %uint %dest 0
+         %30 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %28 %int_1
+         %31 = OpCompositeExtract %v3float %value 1
+               OpStore %30 %31
+         %32 = OpCompositeExtract %uint %dest 0
+         %34 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %32 %int_2
+         %36 = OpCompositeExtract %v3float %value 2
+               OpStore %34 %36
+               OpReturn
+               OpFunctionEnd
+%assign_and_preserve_padding_s = OpFunction %void None %37
+    %value_0 = OpFunctionParameter %_arr_mat3v3float_uint_4
+         %40 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %26
+%var_for_index = OpVariable %_ptr_Function__arr_mat3v3float_uint_4 Function %55
+               OpStore %i %26
+               OpBranch %43
+         %43 = OpLabel
+               OpLoopMerge %44 %45 None
+               OpBranch %46
+         %46 = OpLabel
+         %48 = OpLoad %uint %i
+         %49 = OpULessThan %bool %48 %uint_4
+         %47 = OpLogicalNot %bool %49
+               OpSelectionMerge %51 None
+               OpBranchConditional %47 %52 %51
+         %52 = OpLabel
+               OpBranch %44
+         %51 = OpLabel
+               OpStore %var_for_index %value_0
+         %57 = OpLoad %uint %i
+         %58 = OpCompositeConstruct %_arr_uint_uint_1 %57
+         %59 = OpLoad %uint %i
+         %61 = OpAccessChain %_ptr_Function_mat3v3float %var_for_index %59
+         %62 = OpLoad %mat3v3float %61
+         %56 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %58 %62
+               OpBranch %45
+         %45 = OpLabel
+         %63 = OpLoad %uint %i
+         %64 = OpIAdd %uint %63 %uint_1
+               OpStore %i %64
+               OpBranch %43
+         %44 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %65
+         %67 = OpLabel
+         %70 = OpAccessChain %_ptr_Uniform__arr_mat3v3float_uint_4 %u %uint_0
+         %71 = OpLoad %_arr_mat3v3float_uint_4 %70
+         %68 = OpFunctionCall %void %assign_and_preserve_padding_s %71
+         %75 = OpAccessChain %_ptr_Uniform_mat3v3float %u %uint_0 %int_2
+         %76 = OpLoad %mat3v3float %75
+         %72 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %73 %76
+         %77 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %22
+         %79 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %22 %int_1
+         %80 = OpLoad %v3float %79
+         %81 = OpVectorShuffle %v3float %80 %80 2 0 1
+               OpStore %77 %81
+         %83 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %int_1 %22 %uint_0
+         %85 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %22 %int_1 %uint_0
+         %86 = OpLoad %float %85
+               OpStore %83 %86
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/array/mat4x3_f16/to_storage.wgsl.expected.glsl

@@ -16,6 +16,22 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   f16mat4x3 inner[4];
 } s;
 
+void assign_and_preserve_padding_1_s_X(uint dest[1], f16mat4x3 value) {
+  s.inner[dest[0]][0] = value[0u];
+  s.inner[dest[0]][1] = value[1u];
+  s.inner[dest[0]][2] = value[2u];
+  s.inner[dest[0]][3] = value[3u];
+}
+
+void assign_and_preserve_padding_s(f16mat4x3 value[4]) {
+  {
+    for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+      uint tint_symbol[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+    }
+  }
+}
+
 f16mat4x3 conv_mat4x3_f16(mat4x3_f16 val) {
   return f16mat4x3(val.col0, val.col1, val.col2, val.col3);
 }
@@ -31,8 +47,9 @@ f16mat4x3[4] conv_arr4_mat4x3_f16(mat4x3_f16 val[4]) {
 }
 
 void f() {
-  s.inner = conv_arr4_mat4x3_f16(u.inner);
-  s.inner[1] = conv_mat4x3_f16(u.inner[2u]);
+  assign_and_preserve_padding_s(conv_arr4_mat4x3_f16(u.inner));
+  uint tint_symbol_1[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_1, conv_mat4x3_f16(u.inner[2u]));
   s.inner[1][0] = u.inner[0u].col1.zxy;
   s.inner[1][0].x = u.inner[0u].col1[0u];
 }

test/tint/buffer/uniform/std140/array/mat4x3_f16/to_storage.wgsl.expected.msl

@@ -14,9 +14,22 @@ struct tint_array {
     T elements[N];
 };
 
+void assign_and_preserve_padding_1(device half4x3* const dest, half4x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+  (*(dest))[3u] = value[3u];
+}
+
+void assign_and_preserve_padding(device tint_array<half4x3, 4>* const dest, tint_array<half4x3, 4> value) {
+  for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+    assign_and_preserve_padding_1(&((*(dest))[i]), value[i]);
+  }
+}
+
 kernel void f(device tint_array<half4x3, 4>* tint_symbol [[buffer(1)]], const constant tint_array<half4x3, 4>* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
-  (*(tint_symbol))[1] = (*(tint_symbol_1))[2];
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
+  assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
   (*(tint_symbol))[1][0] = half3((*(tint_symbol_1))[0][1]).zxy;
   (*(tint_symbol))[1][0][0] = (*(tint_symbol_1))[0][1][0];
   return;

test/tint/buffer/uniform/std140/array/mat4x3_f16/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 91
+; Bound: 134
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
@@ -22,13 +22,20 @@
                OpName %u_block "u_block"
                OpMemberName %u_block 0 "inner"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest "dest"
+               OpName %value "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_0 "value"
+               OpName %i "i"
+               OpName %var_for_index "var_for_index"
                OpName %conv_mat4x3_f16 "conv_mat4x3_f16"
                OpName %val "val"
                OpName %conv_arr4_mat4x3_f16 "conv_arr4_mat4x3_f16"
                OpName %val_0 "val"
                OpName %arr "arr"
-               OpName %i "i"
-               OpName %var_for_index "var_for_index"
+               OpName %i_0 "i"
+               OpName %var_for_index_1 "var_for_index_1"
                OpName %f "f"
                OpDecorate %u_block_std140 Block
                OpMemberDecorate %u_block_std140 0 Offset 0
@@ -47,6 +54,7 @@
                OpDecorate %_arr_mat4v3half_uint_4 ArrayStride 32
                OpDecorate %s DescriptorSet 0
                OpDecorate %s Binding 1
+               OpDecorate %_arr_uint_uint_1 ArrayStride 4
        %half = OpTypeFloat 16
      %v3half = OpTypeVector %half 3
  %mat4x3_f16 = OpTypeStruct %v3half %v3half %v3half %v3half
@@ -61,100 +69,160 @@
     %u_block = OpTypeStruct %_arr_mat4v3half_uint_4
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
-         %15 = OpTypeFunction %mat4v3half %mat4x3_f16
-         %24 = OpTypeFunction %_arr_mat4v3half_uint_4 %_arr_mat4x3_f16_uint_4
-%_ptr_Function__arr_mat4v3half_uint_4 = OpTypePointer Function %_arr_mat4v3half_uint_4
-         %30 = OpConstantNull %_arr_mat4v3half_uint_4
-%_ptr_Function_uint = OpTypePointer Function %uint
-         %33 = OpConstantNull %uint
-       %bool = OpTypeBool
-%_ptr_Function__arr_mat4x3_f16_uint_4 = OpTypePointer Function %_arr_mat4x3_f16_uint_4
-         %46 = OpConstantNull %_arr_mat4x3_f16_uint_4
-%_ptr_Function_mat4v3half = OpTypePointer Function %mat4v3half
-%_ptr_Function_mat4x3_f16 = OpTypePointer Function %mat4x3_f16
-     %uint_1 = OpConstant %uint 1
        %void = OpTypeVoid
-         %59 = OpTypeFunction %void
+     %uint_1 = OpConstant %uint 1
+%_arr_uint_uint_1 = OpTypeArray %uint %uint_1
+         %15 = OpTypeFunction %void %_arr_uint_uint_1 %mat4v3half
      %uint_0 = OpConstant %uint 0
-%_ptr_StorageBuffer__arr_mat4v3half_uint_4 = OpTypePointer StorageBuffer %_arr_mat4v3half_uint_4
-%_ptr_Uniform__arr_mat4x3_f16_uint_4 = OpTypePointer Uniform %_arr_mat4x3_f16_uint_4
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_mat4v3half = OpTypePointer StorageBuffer %mat4v3half
-     %uint_2 = OpConstant %uint 2
-%_ptr_Uniform_mat4x3_f16 = OpTypePointer Uniform %mat4x3_f16
-         %79 = OpConstantNull %int
+         %25 = OpConstantNull %int
 %_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
+         %29 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+      %int_2 = OpConstant %int 2
+     %uint_2 = OpConstant %uint 2
+      %int_3 = OpConstant %int 3
+     %uint_3 = OpConstant %uint 3
+         %45 = OpTypeFunction %void %_arr_mat4v3half_uint_4
+%_ptr_Function_uint = OpTypePointer Function %uint
+       %bool = OpTypeBool
+%_ptr_Function__arr_mat4v3half_uint_4 = OpTypePointer Function %_arr_mat4v3half_uint_4
+         %63 = OpConstantNull %_arr_mat4v3half_uint_4
+%_ptr_Function_mat4v3half = OpTypePointer Function %mat4v3half
+         %73 = OpTypeFunction %mat4v3half %mat4x3_f16
+         %82 = OpTypeFunction %_arr_mat4v3half_uint_4 %_arr_mat4x3_f16_uint_4
+%_ptr_Function__arr_mat4x3_f16_uint_4 = OpTypePointer Function %_arr_mat4x3_f16_uint_4
+         %99 = OpConstantNull %_arr_mat4x3_f16_uint_4
+%_ptr_Function_mat4x3_f16 = OpTypePointer Function %mat4x3_f16
+        %110 = OpTypeFunction %void
+%_ptr_Uniform__arr_mat4x3_f16_uint_4 = OpTypePointer Uniform %_arr_mat4x3_f16_uint_4
+        %119 = OpConstantComposite %_arr_uint_uint_1 %uint_1
+%_ptr_Uniform_mat4x3_f16 = OpTypePointer Uniform %mat4x3_f16
 %_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
 %_ptr_StorageBuffer_half = OpTypePointer StorageBuffer %half
 %_ptr_Uniform_half = OpTypePointer Uniform %half
-%conv_mat4x3_f16 = OpFunction %mat4v3half None %15
-        %val = OpFunctionParameter %mat4x3_f16
-         %18 = OpLabel
-         %19 = OpCompositeExtract %v3half %val 0
-         %20 = OpCompositeExtract %v3half %val 1
-         %21 = OpCompositeExtract %v3half %val 2
-         %22 = OpCompositeExtract %v3half %val 3
-         %23 = OpCompositeConstruct %mat4v3half %19 %20 %21 %22
-               OpReturnValue %23
-               OpFunctionEnd
-%conv_arr4_mat4x3_f16 = OpFunction %_arr_mat4v3half_uint_4 None %24
-      %val_0 = OpFunctionParameter %_arr_mat4x3_f16_uint_4
-         %27 = OpLabel
-        %arr = OpVariable %_ptr_Function__arr_mat4v3half_uint_4 Function %30
-          %i = OpVariable %_ptr_Function_uint Function %33
-%var_for_index = OpVariable %_ptr_Function__arr_mat4x3_f16_uint_4 Function %46
-               OpBranch %34
-         %34 = OpLabel
-               OpLoopMerge %35 %36 None
-               OpBranch %37
-         %37 = OpLabel
-         %39 = OpLoad %uint %i
-         %40 = OpULessThan %bool %39 %uint_4
-         %38 = OpLogicalNot %bool %40
-               OpSelectionMerge %42 None
-               OpBranchConditional %38 %43 %42
-         %43 = OpLabel
-               OpBranch %35
-         %42 = OpLabel
-               OpStore %var_for_index %val_0
-         %47 = OpLoad %uint %i
-         %49 = OpAccessChain %_ptr_Function_mat4v3half %arr %47
-         %51 = OpLoad %uint %i
-         %53 = OpAccessChain %_ptr_Function_mat4x3_f16 %var_for_index %51
-         %54 = OpLoad %mat4x3_f16 %53
-         %50 = OpFunctionCall %mat4v3half %conv_mat4x3_f16 %54
-               OpStore %49 %50
-               OpBranch %36
-         %36 = OpLabel
-         %55 = OpLoad %uint %i
-         %57 = OpIAdd %uint %55 %uint_1
-               OpStore %i %57
-               OpBranch %34
-         %35 = OpLabel
-         %58 = OpLoad %_arr_mat4v3half_uint_4 %arr
-               OpReturnValue %58
-               OpFunctionEnd
-          %f = OpFunction %void None %59
-         %62 = OpLabel
-         %65 = OpAccessChain %_ptr_StorageBuffer__arr_mat4v3half_uint_4 %s %uint_0
-         %68 = OpAccessChain %_ptr_Uniform__arr_mat4x3_f16_uint_4 %u %uint_0
-         %69 = OpLoad %_arr_mat4x3_f16_uint_4 %68
-         %66 = OpFunctionCall %_arr_mat4v3half_uint_4 %conv_arr4_mat4x3_f16 %69
-               OpStore %65 %66
-         %73 = OpAccessChain %_ptr_StorageBuffer_mat4v3half %s %uint_0 %int_1
-         %77 = OpAccessChain %_ptr_Uniform_mat4x3_f16 %u %uint_0 %uint_2
-         %78 = OpLoad %mat4x3_f16 %77
-         %74 = OpFunctionCall %mat4v3half %conv_mat4x3_f16 %78
-               OpStore %73 %74
-         %81 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %79
-         %83 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %33 %uint_1
-         %84 = OpLoad %v3half %83
-         %85 = OpVectorShuffle %v3half %84 %84 2 0 1
-               OpStore %81 %85
-         %87 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %int_1 %79 %uint_0
-         %89 = OpAccessChain %_ptr_Uniform_half %u %uint_0 %33 %uint_1 %33
-         %90 = OpLoad %half %89
-               OpStore %87 %90
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %15
+       %dest = OpFunctionParameter %_arr_uint_uint_1
+      %value = OpFunctionParameter %mat4v3half
+         %22 = OpLabel
+         %26 = OpCompositeExtract %uint %dest 0
+         %28 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %26 %25
+         %30 = OpCompositeExtract %v3half %value 0
+               OpStore %28 %30
+         %31 = OpCompositeExtract %uint %dest 0
+         %33 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %31 %int_1
+         %34 = OpCompositeExtract %v3half %value 1
+               OpStore %33 %34
+         %35 = OpCompositeExtract %uint %dest 0
+         %37 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %35 %int_2
+         %39 = OpCompositeExtract %v3half %value 2
+               OpStore %37 %39
+         %40 = OpCompositeExtract %uint %dest 0
+         %42 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %40 %int_3
+         %44 = OpCompositeExtract %v3half %value 3
+               OpStore %42 %44
+               OpReturn
+               OpFunctionEnd
+%assign_and_preserve_padding_s = OpFunction %void None %45
+    %value_0 = OpFunctionParameter %_arr_mat4v3half_uint_4
+         %48 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %29
+%var_for_index = OpVariable %_ptr_Function__arr_mat4v3half_uint_4 Function %63
+               OpStore %i %29
+               OpBranch %51
+         %51 = OpLabel
+               OpLoopMerge %52 %53 None
+               OpBranch %54
+         %54 = OpLabel
+         %56 = OpLoad %uint %i
+         %57 = OpULessThan %bool %56 %uint_4
+         %55 = OpLogicalNot %bool %57
+               OpSelectionMerge %59 None
+               OpBranchConditional %55 %60 %59
+         %60 = OpLabel
+               OpBranch %52
+         %59 = OpLabel
+               OpStore %var_for_index %value_0
+         %65 = OpLoad %uint %i
+         %66 = OpCompositeConstruct %_arr_uint_uint_1 %65
+         %67 = OpLoad %uint %i
+         %69 = OpAccessChain %_ptr_Function_mat4v3half %var_for_index %67
+         %70 = OpLoad %mat4v3half %69
+         %64 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %66 %70
+               OpBranch %53
+         %53 = OpLabel
+         %71 = OpLoad %uint %i
+         %72 = OpIAdd %uint %71 %uint_1
+               OpStore %i %72
+               OpBranch %51
+         %52 = OpLabel
+               OpReturn
+               OpFunctionEnd
+%conv_mat4x3_f16 = OpFunction %mat4v3half None %73
+        %val = OpFunctionParameter %mat4x3_f16
+         %76 = OpLabel
+         %77 = OpCompositeExtract %v3half %val 0
+         %78 = OpCompositeExtract %v3half %val 1
+         %79 = OpCompositeExtract %v3half %val 2
+         %80 = OpCompositeExtract %v3half %val 3
+         %81 = OpCompositeConstruct %mat4v3half %77 %78 %79 %80
+               OpReturnValue %81
+               OpFunctionEnd
+%conv_arr4_mat4x3_f16 = OpFunction %_arr_mat4v3half_uint_4 None %82
+      %val_0 = OpFunctionParameter %_arr_mat4x3_f16_uint_4
+         %85 = OpLabel
+        %arr = OpVariable %_ptr_Function__arr_mat4v3half_uint_4 Function %63
+        %i_0 = OpVariable %_ptr_Function_uint Function %29
+%var_for_index_1 = OpVariable %_ptr_Function__arr_mat4x3_f16_uint_4 Function %99
+               OpBranch %88
+         %88 = OpLabel
+               OpLoopMerge %89 %90 None
+               OpBranch %91
+         %91 = OpLabel
+         %93 = OpLoad %uint %i_0
+         %94 = OpULessThan %bool %93 %uint_4
+         %92 = OpLogicalNot %bool %94
+               OpSelectionMerge %95 None
+               OpBranchConditional %92 %96 %95
+         %96 = OpLabel
+               OpBranch %89
+         %95 = OpLabel
+               OpStore %var_for_index_1 %val_0
+        %100 = OpLoad %uint %i_0
+        %101 = OpAccessChain %_ptr_Function_mat4v3half %arr %100
+        %103 = OpLoad %uint %i_0
+        %105 = OpAccessChain %_ptr_Function_mat4x3_f16 %var_for_index_1 %103
+        %106 = OpLoad %mat4x3_f16 %105
+        %102 = OpFunctionCall %mat4v3half %conv_mat4x3_f16 %106
+               OpStore %101 %102
+               OpBranch %90
+         %90 = OpLabel
+        %107 = OpLoad %uint %i_0
+        %108 = OpIAdd %uint %107 %uint_1
+               OpStore %i_0 %108
+               OpBranch %88
+         %89 = OpLabel
+        %109 = OpLoad %_arr_mat4v3half_uint_4 %arr
+               OpReturnValue %109
+               OpFunctionEnd
+          %f = OpFunction %void None %110
+        %112 = OpLabel
+        %116 = OpAccessChain %_ptr_Uniform__arr_mat4x3_f16_uint_4 %u %uint_0
+        %117 = OpLoad %_arr_mat4x3_f16_uint_4 %116
+        %114 = OpFunctionCall %_arr_mat4v3half_uint_4 %conv_arr4_mat4x3_f16 %117
+        %113 = OpFunctionCall %void %assign_and_preserve_padding_s %114
+        %122 = OpAccessChain %_ptr_Uniform_mat4x3_f16 %u %uint_0 %uint_2
+        %123 = OpLoad %mat4x3_f16 %122
+        %120 = OpFunctionCall %mat4v3half %conv_mat4x3_f16 %123
+        %118 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %119 %120
+        %124 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %25
+        %126 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %29 %uint_1
+        %127 = OpLoad %v3half %126
+        %128 = OpVectorShuffle %v3half %127 %127 2 0 1
+               OpStore %124 %128
+        %130 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %int_1 %25 %uint_0
+        %132 = OpAccessChain %_ptr_Uniform_half %u %uint_0 %29 %uint_1 %29
+        %133 = OpLoad %half %132
+               OpStore %130 %133
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/array/mat4x3_f32/to_storage.wgsl.expected.glsl

@@ -8,9 +8,26 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   mat4x3 inner[4];
 } s;
 
+void assign_and_preserve_padding_1_s_X(uint dest[1], mat4x3 value) {
+  s.inner[dest[0]][0] = value[0u];
+  s.inner[dest[0]][1] = value[1u];
+  s.inner[dest[0]][2] = value[2u];
+  s.inner[dest[0]][3] = value[3u];
+}
+
+void assign_and_preserve_padding_s(mat4x3 value[4]) {
+  {
+    for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+      uint tint_symbol[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+    }
+  }
+}
+
 void f() {
-  s.inner = u.inner;
-  s.inner[1] = u.inner[2];
+  assign_and_preserve_padding_s(u.inner);
+  uint tint_symbol_1[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_1, u.inner[2]);
   s.inner[1][0] = u.inner[0][1].zxy;
   s.inner[1][0].x = u.inner[0][1].x;
 }

test/tint/buffer/uniform/std140/array/mat4x3_f32/to_storage.wgsl.expected.msl

@@ -14,9 +14,22 @@ struct tint_array {
     T elements[N];
 };
 
+void assign_and_preserve_padding_1(device float4x3* const dest, float4x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+  (*(dest))[3u] = value[3u];
+}
+
+void assign_and_preserve_padding(device tint_array<float4x3, 4>* const dest, tint_array<float4x3, 4> value) {
+  for(uint i = 0u; (i < 4u); i = (i + 1u)) {
+    assign_and_preserve_padding_1(&((*(dest))[i]), value[i]);
+  }
+}
+
 kernel void f(device tint_array<float4x3, 4>* tint_symbol [[buffer(1)]], const constant tint_array<float4x3, 4>* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
-  (*(tint_symbol))[1] = (*(tint_symbol_1))[2];
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
+  assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
   (*(tint_symbol))[1][0] = float3((*(tint_symbol_1))[0][1]).zxy;
   (*(tint_symbol))[1][0][0] = (*(tint_symbol_1))[0][1][0];
   return;

test/tint/buffer/uniform/std140/array/mat4x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 42
+; Bound: 92
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -11,6 +11,13 @@
                OpMemberName %u_block 0 "inner"
                OpName %u "u"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest "dest"
+               OpName %value "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_0 "value"
+               OpName %i "i"
+               OpName %var_for_index "var_for_index"
                OpName %f "f"
                OpDecorate %u_block Block
                OpMemberDecorate %u_block 0 Offset 0
@@ -22,6 +29,7 @@
                OpDecorate %u Binding 0
                OpDecorate %s DescriptorSet 0
                OpDecorate %s Binding 1
+               OpDecorate %_arr_uint_uint_1 ArrayStride 4
       %float = OpTypeFloat 32
     %v3float = OpTypeVector %float 3
 %mat4v3float = OpTypeMatrix %v3float 4
@@ -34,38 +42,105 @@
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
        %void = OpTypeVoid
-         %12 = OpTypeFunction %void
+     %uint_1 = OpConstant %uint 1
+%_arr_uint_uint_1 = OpTypeArray %uint %uint_1
+         %12 = OpTypeFunction %void %_arr_uint_uint_1 %mat4v3float
      %uint_0 = OpConstant %uint 0
-%_ptr_StorageBuffer__arr_mat4v3float_uint_4 = OpTypePointer StorageBuffer %_arr_mat4v3float_uint_4
-%_ptr_Uniform__arr_mat4v3float_uint_4 = OpTypePointer Uniform %_arr_mat4v3float_uint_4
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_mat4v3float = OpTypePointer StorageBuffer %mat4v3float
-      %int_2 = OpConstant %int 2
-%_ptr_Uniform_mat4v3float = OpTypePointer Uniform %mat4v3float
-         %30 = OpConstantNull %int
+         %22 = OpConstantNull %int
 %_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
+         %26 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+      %int_2 = OpConstant %int 2
+     %uint_2 = OpConstant %uint 2
+      %int_3 = OpConstant %int 3
+     %uint_3 = OpConstant %uint 3
+         %42 = OpTypeFunction %void %_arr_mat4v3float_uint_4
+%_ptr_Function_uint = OpTypePointer Function %uint
+       %bool = OpTypeBool
+%_ptr_Function__arr_mat4v3float_uint_4 = OpTypePointer Function %_arr_mat4v3float_uint_4
+         %60 = OpConstantNull %_arr_mat4v3float_uint_4
+%_ptr_Function_mat4v3float = OpTypePointer Function %mat4v3float
+         %70 = OpTypeFunction %void
+%_ptr_Uniform__arr_mat4v3float_uint_4 = OpTypePointer Uniform %_arr_mat4v3float_uint_4
+         %78 = OpConstantComposite %_arr_uint_uint_1 %uint_1
+%_ptr_Uniform_mat4v3float = OpTypePointer Uniform %mat4v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
 %_ptr_StorageBuffer_float = OpTypePointer StorageBuffer %float
 %_ptr_Uniform_float = OpTypePointer Uniform %float
-          %f = OpFunction %void None %12
-         %15 = OpLabel
-         %18 = OpAccessChain %_ptr_StorageBuffer__arr_mat4v3float_uint_4 %s %uint_0
-         %20 = OpAccessChain %_ptr_Uniform__arr_mat4v3float_uint_4 %u %uint_0
-         %21 = OpLoad %_arr_mat4v3float_uint_4 %20
-               OpStore %18 %21
-         %25 = OpAccessChain %_ptr_StorageBuffer_mat4v3float %s %uint_0 %int_1
-         %28 = OpAccessChain %_ptr_Uniform_mat4v3float %u %uint_0 %int_2
-         %29 = OpLoad %mat4v3float %28
-               OpStore %25 %29
-         %32 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %30
-         %34 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %30 %int_1
-         %35 = OpLoad %v3float %34
-         %36 = OpVectorShuffle %v3float %35 %35 2 0 1
-               OpStore %32 %36
-         %38 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %int_1 %30 %uint_0
-         %40 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %30 %int_1 %uint_0
-         %41 = OpLoad %float %40
-               OpStore %38 %41
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %12
+       %dest = OpFunctionParameter %_arr_uint_uint_1
+      %value = OpFunctionParameter %mat4v3float
+         %19 = OpLabel
+         %23 = OpCompositeExtract %uint %dest 0
+         %25 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %23 %22
+         %27 = OpCompositeExtract %v3float %value 0
+               OpStore %25 %27
+         %28 = OpCompositeExtract %uint %dest 0
+         %30 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %28 %int_1
+         %31 = OpCompositeExtract %v3float %value 1
+               OpStore %30 %31
+         %32 = OpCompositeExtract %uint %dest 0
+         %34 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %32 %int_2
+         %36 = OpCompositeExtract %v3float %value 2
+               OpStore %34 %36
+         %37 = OpCompositeExtract %uint %dest 0
+         %39 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %37 %int_3
+         %41 = OpCompositeExtract %v3float %value 3
+               OpStore %39 %41
+               OpReturn
+               OpFunctionEnd
+%assign_and_preserve_padding_s = OpFunction %void None %42
+    %value_0 = OpFunctionParameter %_arr_mat4v3float_uint_4
+         %45 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %26
+%var_for_index = OpVariable %_ptr_Function__arr_mat4v3float_uint_4 Function %60
+               OpStore %i %26
+               OpBranch %48
+         %48 = OpLabel
+               OpLoopMerge %49 %50 None
+               OpBranch %51
+         %51 = OpLabel
+         %53 = OpLoad %uint %i
+         %54 = OpULessThan %bool %53 %uint_4
+         %52 = OpLogicalNot %bool %54
+               OpSelectionMerge %56 None
+               OpBranchConditional %52 %57 %56
+         %57 = OpLabel
+               OpBranch %49
+         %56 = OpLabel
+               OpStore %var_for_index %value_0
+         %62 = OpLoad %uint %i
+         %63 = OpCompositeConstruct %_arr_uint_uint_1 %62
+         %64 = OpLoad %uint %i
+         %66 = OpAccessChain %_ptr_Function_mat4v3float %var_for_index %64
+         %67 = OpLoad %mat4v3float %66
+         %61 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %63 %67
+               OpBranch %50
+         %50 = OpLabel
+         %68 = OpLoad %uint %i
+         %69 = OpIAdd %uint %68 %uint_1
+               OpStore %i %69
+               OpBranch %48
+         %49 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %70
+         %72 = OpLabel
+         %75 = OpAccessChain %_ptr_Uniform__arr_mat4v3float_uint_4 %u %uint_0
+         %76 = OpLoad %_arr_mat4v3float_uint_4 %75
+         %73 = OpFunctionCall %void %assign_and_preserve_padding_s %76
+         %80 = OpAccessChain %_ptr_Uniform_mat4v3float %u %uint_0 %int_2
+         %81 = OpLoad %mat4v3float %80
+         %77 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %78 %81
+         %82 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %22
+         %84 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %22 %int_1
+         %85 = OpLoad %v3float %84
+         %86 = OpVectorShuffle %v3float %85 %85 2 0 1
+               OpStore %82 %86
+         %88 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %int_1 %22 %uint_0
+         %90 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %22 %int_1 %uint_0
+         %91 = OpLoad %float %90
+               OpStore %88 %91
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/struct/mat2x3_f16/to_storage.wgsl.expected.glsl

@@ -74,17 +74,23 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   S inner[4];
 } s;
 
+void assign_and_preserve_padding_2_s_X_m(uint dest[1], f16mat2x3 value) {
+  s.inner[dest[0]].m[0] = value[0u];
+  s.inner[dest[0]].m[1] = value[1u];
+}
+
 void assign_and_preserve_padding_1_s_X(uint dest[1], S value) {
   s.inner[dest[0]].before = value.before;
-  s.inner[dest[0]].m = value.m;
+  uint tint_symbol[1] = uint[1](dest[0u]);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol, value.m);
   s.inner[dest[0]].after = value.after;
 }
 
 void assign_and_preserve_padding_s(S value[4]) {
   {
     for(uint i = 0u; (i < 4u); i = (i + 1u)) {
-      uint tint_symbol[1] = uint[1](i);
-      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+      uint tint_symbol_1[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol_1, value[i]);
     }
   }
 }
@@ -109,9 +115,10 @@ f16mat2x3 load_u_inner_2_m() {
 
 void f() {
   assign_and_preserve_padding_s(conv_arr4_S(u.inner));
-  uint tint_symbol_1[1] = uint[1](1u);
-  assign_and_preserve_padding_1_s_X(tint_symbol_1, conv_S(u.inner[2u]));
-  s.inner[3].m = load_u_inner_2_m();
+  uint tint_symbol_2[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_2, conv_S(u.inner[2u]));
+  uint tint_symbol_3[1] = uint[1](3u);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol_3, load_u_inner_2_m());
   s.inner[1].m[0] = u.inner[0u].m_1.zxy;
 }
 

test/tint/buffer/uniform/std140/struct/mat2x3_f16/to_storage.wgsl.expected.msl

@@ -23,9 +23,14 @@ struct S {
   /* 0x0044 */ tint_array<int8_t, 60> tint_pad_2;
 };
 
+void assign_and_preserve_padding_2(device half2x3* const dest, half2x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+}
+
 void assign_and_preserve_padding_1(device S* const dest, S value) {
   (*(dest)).before = value.before;
-  (*(dest)).m = value.m;
+  assign_and_preserve_padding_2(&((*(dest)).m), value.m);
   (*(dest)).after = value.after;
 }
 
@@ -38,7 +43,7 @@ void assign_and_preserve_padding(device tint_array<S, 4>* const dest, tint_array
 kernel void f(device tint_array<S, 4>* tint_symbol [[buffer(1)]], const constant tint_array<S, 4>* tint_symbol_1 [[buffer(0)]]) {
   assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
-  (*(tint_symbol))[3].m = (*(tint_symbol_1))[2].m;
+  assign_and_preserve_padding_2(&((*(tint_symbol))[3].m), (*(tint_symbol_1))[2].m);
   (*(tint_symbol))[1].m[0] = half3((*(tint_symbol_1))[0].m[1]).zxy;
   return;
 }

test/tint/buffer/uniform/std140/struct/mat2x3_f16/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 142
+; Bound: 154
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
@@ -26,11 +26,14 @@
                OpMemberName %S 1 "m"
                OpMemberName %S 2 "after"
                OpName %s "s"
-               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %assign_and_preserve_padding_2_s_X_m "assign_and_preserve_padding_2_s_X_m"
                OpName %dest "dest"
                OpName %value "value"
-               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest_0 "dest"
                OpName %value_0 "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_1 "value"
                OpName %i "i"
                OpName %var_for_index "var_for_index"
                OpName %conv_S "conv_S"
@@ -82,161 +85,175 @@
        %void = OpTypeVoid
      %uint_1 = OpConstant %uint 1
 %_arr_uint_uint_1 = OpTypeArray %uint %uint_1
-         %17 = OpTypeFunction %void %_arr_uint_uint_1 %S
+         %17 = OpTypeFunction %void %_arr_uint_uint_1 %mat2v3half
      %uint_0 = OpConstant %uint 0
          %26 = OpConstantNull %int
+%_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
+         %30 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+         %36 = OpTypeFunction %void %_arr_uint_uint_1 %S
 %_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
-%_ptr_StorageBuffer_mat2v3half = OpTypePointer StorageBuffer %mat2v3half
      %uint_2 = OpConstant %uint 2
-         %39 = OpTypeFunction %void %_arr_S_uint_4
-         %43 = OpConstantNull %uint
+         %53 = OpTypeFunction %void %_arr_S_uint_4
 %_ptr_Function_uint = OpTypePointer Function %uint
        %bool = OpTypeBool
 %_ptr_Function__arr_S_uint_4 = OpTypePointer Function %_arr_S_uint_4
-         %58 = OpConstantNull %_arr_S_uint_4
+         %71 = OpConstantNull %_arr_S_uint_4
 %_ptr_Function_S = OpTypePointer Function %S
-         %68 = OpTypeFunction %S %S_std140
-         %78 = OpTypeFunction %_arr_S_uint_4 %_arr_S_std140_uint_4
+         %81 = OpTypeFunction %S %S_std140
+         %91 = OpTypeFunction %_arr_S_uint_4 %_arr_S_std140_uint_4
 %_ptr_Function__arr_S_std140_uint_4 = OpTypePointer Function %_arr_S_std140_uint_4
-         %95 = OpConstantNull %_arr_S_std140_uint_4
+        %108 = OpConstantNull %_arr_S_std140_uint_4
 %_ptr_Function_S_std140 = OpTypePointer Function %S_std140
-        %106 = OpTypeFunction %mat2v3half
+        %119 = OpTypeFunction %mat2v3half
 %_ptr_Uniform_S_std140 = OpTypePointer Uniform %S_std140
 %_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
-        %120 = OpTypeFunction %void
+        %133 = OpTypeFunction %void
 %_ptr_Uniform__arr_S_std140_uint_4 = OpTypePointer Uniform %_arr_S_std140_uint_4
-        %129 = OpConstantComposite %_arr_uint_uint_1 %uint_1
-      %int_3 = OpConstant %int 3
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
-%assign_and_preserve_padding_1_s_X = OpFunction %void None %17
+        %142 = OpConstantComposite %_arr_uint_uint_1 %uint_1
+     %uint_3 = OpConstant %uint 3
+        %148 = OpConstantComposite %_arr_uint_uint_1 %uint_3
+%assign_and_preserve_padding_2_s_X_m = OpFunction %void None %17
        %dest = OpFunctionParameter %_arr_uint_uint_1
-      %value = OpFunctionParameter %S
+      %value = OpFunctionParameter %mat2v3half
          %24 = OpLabel
          %27 = OpCompositeExtract %uint %dest 0
-         %29 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %27 %uint_0
-         %30 = OpCompositeExtract %int %value 0
-               OpStore %29 %30
-         %31 = OpCompositeExtract %uint %dest 0
-         %33 = OpAccessChain %_ptr_StorageBuffer_mat2v3half %s %uint_0 %31 %uint_1
-         %34 = OpCompositeExtract %mat2v3half %value 1
-               OpStore %33 %34
-         %35 = OpCompositeExtract %uint %dest 0
-         %37 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %35 %uint_2
-         %38 = OpCompositeExtract %int %value 2
-               OpStore %37 %38
+         %29 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %27 %uint_1 %26
+         %31 = OpCompositeExtract %v3half %value 0
+               OpStore %29 %31
+         %32 = OpCompositeExtract %uint %dest 0
+         %34 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %32 %uint_1 %int_1
+         %35 = OpCompositeExtract %v3half %value 1
+               OpStore %34 %35
                OpReturn
                OpFunctionEnd
-%assign_and_preserve_padding_s = OpFunction %void None %39
-    %value_0 = OpFunctionParameter %_arr_S_uint_4
-         %42 = OpLabel
-          %i = OpVariable %_ptr_Function_uint Function %43
-%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %58
-               OpStore %i %43
-               OpBranch %46
-         %46 = OpLabel
-               OpLoopMerge %47 %48 None
-               OpBranch %49
-         %49 = OpLabel
-         %51 = OpLoad %uint %i
-         %52 = OpULessThan %bool %51 %uint_4
-         %50 = OpLogicalNot %bool %52
-               OpSelectionMerge %54 None
-               OpBranchConditional %50 %55 %54
-         %55 = OpLabel
-               OpBranch %47
-         %54 = OpLabel
-               OpStore %var_for_index %value_0
-         %60 = OpLoad %uint %i
-         %61 = OpCompositeConstruct %_arr_uint_uint_1 %60
-         %62 = OpLoad %uint %i
-         %64 = OpAccessChain %_ptr_Function_S %var_for_index %62
-         %65 = OpLoad %S %64
-         %59 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %61 %65
-               OpBranch %48
-         %48 = OpLabel
-         %66 = OpLoad %uint %i
-         %67 = OpIAdd %uint %66 %uint_1
-               OpStore %i %67
-               OpBranch %46
-         %47 = OpLabel
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %36
+     %dest_0 = OpFunctionParameter %_arr_uint_uint_1
+    %value_0 = OpFunctionParameter %S
+         %40 = OpLabel
+         %41 = OpCompositeExtract %uint %dest_0 0
+         %43 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %41 %uint_0
+         %44 = OpCompositeExtract %int %value_0 0
+               OpStore %43 %44
+         %46 = OpCompositeExtract %uint %dest_0 0
+         %47 = OpCompositeConstruct %_arr_uint_uint_1 %46
+         %48 = OpCompositeExtract %mat2v3half %value_0 1
+         %45 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %47 %48
+         %49 = OpCompositeExtract %uint %dest_0 0
+         %51 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %49 %uint_2
+         %52 = OpCompositeExtract %int %value_0 2
+               OpStore %51 %52
                OpReturn
                OpFunctionEnd
-     %conv_S = OpFunction %S None %68
+%assign_and_preserve_padding_s = OpFunction %void None %53
+    %value_1 = OpFunctionParameter %_arr_S_uint_4
+         %56 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %30
+%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %71
+               OpStore %i %30
+               OpBranch %59
+         %59 = OpLabel
+               OpLoopMerge %60 %61 None
+               OpBranch %62
+         %62 = OpLabel
+         %64 = OpLoad %uint %i
+         %65 = OpULessThan %bool %64 %uint_4
+         %63 = OpLogicalNot %bool %65
+               OpSelectionMerge %67 None
+               OpBranchConditional %63 %68 %67
+         %68 = OpLabel
+               OpBranch %60
+         %67 = OpLabel
+               OpStore %var_for_index %value_1
+         %73 = OpLoad %uint %i
+         %74 = OpCompositeConstruct %_arr_uint_uint_1 %73
+         %75 = OpLoad %uint %i
+         %77 = OpAccessChain %_ptr_Function_S %var_for_index %75
+         %78 = OpLoad %S %77
+         %72 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %74 %78
+               OpBranch %61
+         %61 = OpLabel
+         %79 = OpLoad %uint %i
+         %80 = OpIAdd %uint %79 %uint_1
+               OpStore %i %80
+               OpBranch %59
+         %60 = OpLabel
+               OpReturn
+               OpFunctionEnd
+     %conv_S = OpFunction %S None %81
         %val = OpFunctionParameter %S_std140
-         %71 = OpLabel
-         %72 = OpCompositeExtract %int %val 0
-         %73 = OpCompositeExtract %v3half %val 1
-         %74 = OpCompositeExtract %v3half %val 2
-         %75 = OpCompositeConstruct %mat2v3half %73 %74
-         %76 = OpCompositeExtract %int %val 3
-         %77 = OpCompositeConstruct %S %72 %75 %76
-               OpReturnValue %77
-               OpFunctionEnd
-%conv_arr4_S = OpFunction %_arr_S_uint_4 None %78
-      %val_0 = OpFunctionParameter %_arr_S_std140_uint_4
-         %81 = OpLabel
-        %arr = OpVariable %_ptr_Function__arr_S_uint_4 Function %58
-        %i_0 = OpVariable %_ptr_Function_uint Function %43
-%var_for_index_1 = OpVariable %_ptr_Function__arr_S_std140_uint_4 Function %95
-               OpBranch %84
          %84 = OpLabel
-               OpLoopMerge %85 %86 None
-               OpBranch %87
-         %87 = OpLabel
-         %89 = OpLoad %uint %i_0
-         %90 = OpULessThan %bool %89 %uint_4
-         %88 = OpLogicalNot %bool %90
-               OpSelectionMerge %91 None
-               OpBranchConditional %88 %92 %91
-         %92 = OpLabel
-               OpBranch %85
-         %91 = OpLabel
+         %85 = OpCompositeExtract %int %val 0
+         %86 = OpCompositeExtract %v3half %val 1
+         %87 = OpCompositeExtract %v3half %val 2
+         %88 = OpCompositeConstruct %mat2v3half %86 %87
+         %89 = OpCompositeExtract %int %val 3
+         %90 = OpCompositeConstruct %S %85 %88 %89
+               OpReturnValue %90
+               OpFunctionEnd
+%conv_arr4_S = OpFunction %_arr_S_uint_4 None %91
+      %val_0 = OpFunctionParameter %_arr_S_std140_uint_4
+         %94 = OpLabel
+        %arr = OpVariable %_ptr_Function__arr_S_uint_4 Function %71
+        %i_0 = OpVariable %_ptr_Function_uint Function %30
+%var_for_index_1 = OpVariable %_ptr_Function__arr_S_std140_uint_4 Function %108
+               OpBranch %97
+         %97 = OpLabel
+               OpLoopMerge %98 %99 None
+               OpBranch %100
+        %100 = OpLabel
+        %102 = OpLoad %uint %i_0
+        %103 = OpULessThan %bool %102 %uint_4
+        %101 = OpLogicalNot %bool %103
+               OpSelectionMerge %104 None
+               OpBranchConditional %101 %105 %104
+        %105 = OpLabel
+               OpBranch %98
+        %104 = OpLabel
                OpStore %var_for_index_1 %val_0
-         %96 = OpLoad %uint %i_0
-         %97 = OpAccessChain %_ptr_Function_S %arr %96
-         %99 = OpLoad %uint %i_0
-        %101 = OpAccessChain %_ptr_Function_S_std140 %var_for_index_1 %99
-        %102 = OpLoad %S_std140 %101
-         %98 = OpFunctionCall %S %conv_S %102
-               OpStore %97 %98
-               OpBranch %86
-         %86 = OpLabel
-        %103 = OpLoad %uint %i_0
-        %104 = OpIAdd %uint %103 %uint_1
-               OpStore %i_0 %104
-               OpBranch %84
-         %85 = OpLabel
-        %105 = OpLoad %_arr_S_uint_4 %arr
-               OpReturnValue %105
+        %109 = OpLoad %uint %i_0
+        %110 = OpAccessChain %_ptr_Function_S %arr %109
+        %112 = OpLoad %uint %i_0
+        %114 = OpAccessChain %_ptr_Function_S_std140 %var_for_index_1 %112
+        %115 = OpLoad %S_std140 %114
+        %111 = OpFunctionCall %S %conv_S %115
+               OpStore %110 %111
+               OpBranch %99
+         %99 = OpLabel
+        %116 = OpLoad %uint %i_0
+        %117 = OpIAdd %uint %116 %uint_1
+               OpStore %i_0 %117
+               OpBranch %97
+         %98 = OpLabel
+        %118 = OpLoad %_arr_S_uint_4 %arr
+               OpReturnValue %118
                OpFunctionEnd
-%load_u_inner_2_m = OpFunction %mat2v3half None %106
-        %108 = OpLabel
-        %111 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
-        %114 = OpAccessChain %_ptr_Uniform_v3half %111 %uint_1
-        %115 = OpLoad %v3half %114
-        %117 = OpAccessChain %_ptr_Uniform_v3half %111 %uint_2
-        %118 = OpLoad %v3half %117
-        %119 = OpCompositeConstruct %mat2v3half %115 %118
-               OpReturnValue %119
+%load_u_inner_2_m = OpFunction %mat2v3half None %119
+        %121 = OpLabel
+        %124 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
+        %127 = OpAccessChain %_ptr_Uniform_v3half %124 %uint_1
+        %128 = OpLoad %v3half %127
+        %130 = OpAccessChain %_ptr_Uniform_v3half %124 %uint_2
+        %131 = OpLoad %v3half %130
+        %132 = OpCompositeConstruct %mat2v3half %128 %131
+               OpReturnValue %132
                OpFunctionEnd
-          %f = OpFunction %void None %120
-        %122 = OpLabel
-        %126 = OpAccessChain %_ptr_Uniform__arr_S_std140_uint_4 %u %uint_0
-        %127 = OpLoad %_arr_S_std140_uint_4 %126
-        %124 = OpFunctionCall %_arr_S_uint_4 %conv_arr4_S %127
-        %123 = OpFunctionCall %void %assign_and_preserve_padding_s %124
-        %131 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
-        %132 = OpLoad %S_std140 %131
-        %130 = OpFunctionCall %S %conv_S %132
-        %128 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %129 %130
-        %134 = OpAccessChain %_ptr_StorageBuffer_mat2v3half %s %uint_0 %int_3 %uint_1
-        %135 = OpFunctionCall %mat2v3half %load_u_inner_2_m
-               OpStore %134 %135
-        %138 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %uint_1 %26
-        %139 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %43 %uint_2
-        %140 = OpLoad %v3half %139
-        %141 = OpVectorShuffle %v3half %140 %140 2 0 1
-               OpStore %138 %141
+          %f = OpFunction %void None %133
+        %135 = OpLabel
+        %139 = OpAccessChain %_ptr_Uniform__arr_S_std140_uint_4 %u %uint_0
+        %140 = OpLoad %_arr_S_std140_uint_4 %139
+        %137 = OpFunctionCall %_arr_S_uint_4 %conv_arr4_S %140
+        %136 = OpFunctionCall %void %assign_and_preserve_padding_s %137
+        %144 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
+        %145 = OpLoad %S_std140 %144
+        %143 = OpFunctionCall %S %conv_S %145
+        %141 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %142 %143
+        %149 = OpFunctionCall %mat2v3half %load_u_inner_2_m
+        %146 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %148 %149
+        %150 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %uint_1 %26
+        %151 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %30 %uint_2
+        %152 = OpLoad %v3half %151
+        %153 = OpVectorShuffle %v3half %152 %152 2 0 1
+               OpStore %150 %153
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/struct/mat2x3_f32/to_storage.wgsl.expected.glsl

@@ -36,26 +36,33 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   S inner[4];
 } s;
 
+void assign_and_preserve_padding_2_s_X_m(uint dest[1], mat2x3 value) {
+  s.inner[dest[0]].m[0] = value[0u];
+  s.inner[dest[0]].m[1] = value[1u];
+}
+
 void assign_and_preserve_padding_1_s_X(uint dest[1], S value) {
   s.inner[dest[0]].before = value.before;
-  s.inner[dest[0]].m = value.m;
+  uint tint_symbol[1] = uint[1](dest[0u]);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol, value.m);
   s.inner[dest[0]].after = value.after;
 }
 
 void assign_and_preserve_padding_s(S value[4]) {
   {
     for(uint i = 0u; (i < 4u); i = (i + 1u)) {
-      uint tint_symbol[1] = uint[1](i);
-      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+      uint tint_symbol_1[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol_1, value[i]);
     }
   }
 }
 
 void f() {
   assign_and_preserve_padding_s(u.inner);
-  uint tint_symbol_1[1] = uint[1](1u);
-  assign_and_preserve_padding_1_s_X(tint_symbol_1, u.inner[2]);
-  s.inner[3].m = u.inner[2].m;
+  uint tint_symbol_2[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_2, u.inner[2]);
+  uint tint_symbol_3[1] = uint[1](3u);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol_3, u.inner[2].m);
   s.inner[1].m[0] = u.inner[0].m[1].zxy;
 }
 

test/tint/buffer/uniform/std140/struct/mat2x3_f32/to_storage.wgsl.expected.msl

@@ -23,9 +23,14 @@ struct S {
   /* 0x0044 */ tint_array<int8_t, 60> tint_pad_2;
 };
 
+void assign_and_preserve_padding_2(device float2x3* const dest, float2x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+}
+
 void assign_and_preserve_padding_1(device S* const dest, S value) {
   (*(dest)).before = value.before;
-  (*(dest)).m = value.m;
+  assign_and_preserve_padding_2(&((*(dest)).m), value.m);
   (*(dest)).after = value.after;
 }
 
@@ -38,7 +43,7 @@ void assign_and_preserve_padding(device tint_array<S, 4>* const dest, tint_array
 kernel void f(device tint_array<S, 4>* tint_symbol [[buffer(1)]], const constant tint_array<S, 4>* tint_symbol_1 [[buffer(0)]]) {
   assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
-  (*(tint_symbol))[3].m = (*(tint_symbol_1))[2].m;
+  assign_and_preserve_padding_2(&((*(tint_symbol))[3].m), (*(tint_symbol_1))[2].m);
   (*(tint_symbol))[1].m[0] = float3((*(tint_symbol_1))[0].m[1]).zxy;
   return;
 }

test/tint/buffer/uniform/std140/struct/mat2x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 90
+; Bound: 102
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -15,11 +15,14 @@
                OpMemberName %S 2 "after"
                OpName %u "u"
                OpName %s "s"
-               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %assign_and_preserve_padding_2_s_X_m "assign_and_preserve_padding_2_s_X_m"
                OpName %dest "dest"
                OpName %value "value"
-               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest_0 "dest"
                OpName %value_0 "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_1 "value"
                OpName %i "i"
                OpName %var_for_index "var_for_index"
                OpName %f "f"
@@ -53,98 +56,112 @@
        %void = OpTypeVoid
      %uint_1 = OpConstant %uint 1
 %_arr_uint_uint_1 = OpTypeArray %uint %uint_1
-         %14 = OpTypeFunction %void %_arr_uint_uint_1 %S
+         %14 = OpTypeFunction %void %_arr_uint_uint_1 %mat2v3float
      %uint_0 = OpConstant %uint 0
          %23 = OpConstantNull %int
+%_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
+         %27 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+         %33 = OpTypeFunction %void %_arr_uint_uint_1 %S
 %_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
-%_ptr_StorageBuffer_mat2v3float = OpTypePointer StorageBuffer %mat2v3float
      %uint_2 = OpConstant %uint 2
-         %36 = OpTypeFunction %void %_arr_S_uint_4
-         %40 = OpConstantNull %uint
+         %50 = OpTypeFunction %void %_arr_S_uint_4
 %_ptr_Function_uint = OpTypePointer Function %uint
        %bool = OpTypeBool
 %_ptr_Function__arr_S_uint_4 = OpTypePointer Function %_arr_S_uint_4
-         %55 = OpConstantNull %_arr_S_uint_4
+         %68 = OpConstantNull %_arr_S_uint_4
 %_ptr_Function_S = OpTypePointer Function %S
-         %65 = OpTypeFunction %void
+         %78 = OpTypeFunction %void
 %_ptr_Uniform__arr_S_uint_4 = OpTypePointer Uniform %_arr_S_uint_4
-         %73 = OpConstantComposite %_arr_uint_uint_1 %uint_1
+         %86 = OpConstantComposite %_arr_uint_uint_1 %uint_1
       %int_2 = OpConstant %int 2
 %_ptr_Uniform_S = OpTypePointer Uniform %S
-      %int_3 = OpConstant %int 3
+     %uint_3 = OpConstant %uint 3
+         %93 = OpConstantComposite %_arr_uint_uint_1 %uint_3
 %_ptr_Uniform_mat2v3float = OpTypePointer Uniform %mat2v3float
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
-%assign_and_preserve_padding_1_s_X = OpFunction %void None %14
+%assign_and_preserve_padding_2_s_X_m = OpFunction %void None %14
        %dest = OpFunctionParameter %_arr_uint_uint_1
-      %value = OpFunctionParameter %S
+      %value = OpFunctionParameter %mat2v3float
          %21 = OpLabel
          %24 = OpCompositeExtract %uint %dest 0
-         %26 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %24 %uint_0
-         %27 = OpCompositeExtract %int %value 0
-               OpStore %26 %27
-         %28 = OpCompositeExtract %uint %dest 0
-         %30 = OpAccessChain %_ptr_StorageBuffer_mat2v3float %s %uint_0 %28 %uint_1
-         %31 = OpCompositeExtract %mat2v3float %value 1
-               OpStore %30 %31
-         %32 = OpCompositeExtract %uint %dest 0
-         %34 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %32 %uint_2
-         %35 = OpCompositeExtract %int %value 2
-               OpStore %34 %35
+         %26 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %24 %uint_1 %23
+         %28 = OpCompositeExtract %v3float %value 0
+               OpStore %26 %28
+         %29 = OpCompositeExtract %uint %dest 0
+         %31 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %29 %uint_1 %int_1
+         %32 = OpCompositeExtract %v3float %value 1
+               OpStore %31 %32
                OpReturn
                OpFunctionEnd
-%assign_and_preserve_padding_s = OpFunction %void None %36
-    %value_0 = OpFunctionParameter %_arr_S_uint_4
-         %39 = OpLabel
-          %i = OpVariable %_ptr_Function_uint Function %40
-%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %55
-               OpStore %i %40
-               OpBranch %43
-         %43 = OpLabel
-               OpLoopMerge %44 %45 None
-               OpBranch %46
-         %46 = OpLabel
-         %48 = OpLoad %uint %i
-         %49 = OpULessThan %bool %48 %uint_4
-         %47 = OpLogicalNot %bool %49
-               OpSelectionMerge %51 None
-               OpBranchConditional %47 %52 %51
-         %52 = OpLabel
-               OpBranch %44
-         %51 = OpLabel
-               OpStore %var_for_index %value_0
-         %57 = OpLoad %uint %i
-         %58 = OpCompositeConstruct %_arr_uint_uint_1 %57
-         %59 = OpLoad %uint %i
-         %61 = OpAccessChain %_ptr_Function_S %var_for_index %59
-         %62 = OpLoad %S %61
-         %56 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %58 %62
-               OpBranch %45
-         %45 = OpLabel
-         %63 = OpLoad %uint %i
-         %64 = OpIAdd %uint %63 %uint_1
-               OpStore %i %64
-               OpBranch %43
-         %44 = OpLabel
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %33
+     %dest_0 = OpFunctionParameter %_arr_uint_uint_1
+    %value_0 = OpFunctionParameter %S
+         %37 = OpLabel
+         %38 = OpCompositeExtract %uint %dest_0 0
+         %40 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %38 %uint_0
+         %41 = OpCompositeExtract %int %value_0 0
+               OpStore %40 %41
+         %43 = OpCompositeExtract %uint %dest_0 0
+         %44 = OpCompositeConstruct %_arr_uint_uint_1 %43
+         %45 = OpCompositeExtract %mat2v3float %value_0 1
+         %42 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %44 %45
+         %46 = OpCompositeExtract %uint %dest_0 0
+         %48 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %46 %uint_2
+         %49 = OpCompositeExtract %int %value_0 2
+               OpStore %48 %49
                OpReturn
                OpFunctionEnd
-          %f = OpFunction %void None %65
-         %67 = OpLabel
-         %70 = OpAccessChain %_ptr_Uniform__arr_S_uint_4 %u %uint_0
-         %71 = OpLoad %_arr_S_uint_4 %70
-         %68 = OpFunctionCall %void %assign_and_preserve_padding_s %71
-         %76 = OpAccessChain %_ptr_Uniform_S %u %uint_0 %int_2
-         %77 = OpLoad %S %76
-         %72 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %73 %77
-         %79 = OpAccessChain %_ptr_StorageBuffer_mat2v3float %s %uint_0 %int_3 %uint_1
-         %81 = OpAccessChain %_ptr_Uniform_mat2v3float %u %uint_0 %int_2 %uint_1
-         %82 = OpLoad %mat2v3float %81
-               OpStore %79 %82
-         %85 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %uint_1 %23
-         %87 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %23 %uint_1 %int_1
-         %88 = OpLoad %v3float %87
-         %89 = OpVectorShuffle %v3float %88 %88 2 0 1
-               OpStore %85 %89
+%assign_and_preserve_padding_s = OpFunction %void None %50
+    %value_1 = OpFunctionParameter %_arr_S_uint_4
+         %53 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %27
+%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %68
+               OpStore %i %27
+               OpBranch %56
+         %56 = OpLabel
+               OpLoopMerge %57 %58 None
+               OpBranch %59
+         %59 = OpLabel
+         %61 = OpLoad %uint %i
+         %62 = OpULessThan %bool %61 %uint_4
+         %60 = OpLogicalNot %bool %62
+               OpSelectionMerge %64 None
+               OpBranchConditional %60 %65 %64
+         %65 = OpLabel
+               OpBranch %57
+         %64 = OpLabel
+               OpStore %var_for_index %value_1
+         %70 = OpLoad %uint %i
+         %71 = OpCompositeConstruct %_arr_uint_uint_1 %70
+         %72 = OpLoad %uint %i
+         %74 = OpAccessChain %_ptr_Function_S %var_for_index %72
+         %75 = OpLoad %S %74
+         %69 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %71 %75
+               OpBranch %58
+         %58 = OpLabel
+         %76 = OpLoad %uint %i
+         %77 = OpIAdd %uint %76 %uint_1
+               OpStore %i %77
+               OpBranch %56
+         %57 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %78
+         %80 = OpLabel
+         %83 = OpAccessChain %_ptr_Uniform__arr_S_uint_4 %u %uint_0
+         %84 = OpLoad %_arr_S_uint_4 %83
+         %81 = OpFunctionCall %void %assign_and_preserve_padding_s %84
+         %89 = OpAccessChain %_ptr_Uniform_S %u %uint_0 %int_2
+         %90 = OpLoad %S %89
+         %85 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %86 %90
+         %95 = OpAccessChain %_ptr_Uniform_mat2v3float %u %uint_0 %int_2 %uint_1
+         %96 = OpLoad %mat2v3float %95
+         %91 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %93 %96
+         %97 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %uint_1 %23
+         %99 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %23 %uint_1 %int_1
+        %100 = OpLoad %v3float %99
+        %101 = OpVectorShuffle %v3float %100 %100 2 0 1
+               OpStore %97 %101
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/struct/mat3x3_f16/to_storage.wgsl.expected.glsl

@@ -71,17 +71,24 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   S inner[4];
 } s;
 
+void assign_and_preserve_padding_2_s_X_m(uint dest[1], f16mat3 value) {
+  s.inner[dest[0]].m[0] = value[0u];
+  s.inner[dest[0]].m[1] = value[1u];
+  s.inner[dest[0]].m[2] = value[2u];
+}
+
 void assign_and_preserve_padding_1_s_X(uint dest[1], S value) {
   s.inner[dest[0]].before = value.before;
-  s.inner[dest[0]].m = value.m;
+  uint tint_symbol[1] = uint[1](dest[0u]);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol, value.m);
   s.inner[dest[0]].after = value.after;
 }
 
 void assign_and_preserve_padding_s(S value[4]) {
   {
     for(uint i = 0u; (i < 4u); i = (i + 1u)) {
-      uint tint_symbol[1] = uint[1](i);
-      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+      uint tint_symbol_1[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol_1, value[i]);
     }
   }
 }
@@ -106,9 +113,10 @@ f16mat3 load_u_inner_2_m() {
 
 void f() {
   assign_and_preserve_padding_s(conv_arr4_S(u.inner));
-  uint tint_symbol_1[1] = uint[1](1u);
-  assign_and_preserve_padding_1_s_X(tint_symbol_1, conv_S(u.inner[2u]));
-  s.inner[3].m = load_u_inner_2_m();
+  uint tint_symbol_2[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_2, conv_S(u.inner[2u]));
+  uint tint_symbol_3[1] = uint[1](3u);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol_3, load_u_inner_2_m());
   s.inner[1].m[0] = u.inner[0u].m_1.zxy;
 }
 

test/tint/buffer/uniform/std140/struct/mat3x3_f16/to_storage.wgsl.expected.msl

@@ -23,9 +23,15 @@ struct S {
   /* 0x0044 */ tint_array<int8_t, 60> tint_pad_2;
 };
 
+void assign_and_preserve_padding_2(device half3x3* const dest, half3x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+}
+
 void assign_and_preserve_padding_1(device S* const dest, S value) {
   (*(dest)).before = value.before;
-  (*(dest)).m = value.m;
+  assign_and_preserve_padding_2(&((*(dest)).m), value.m);
   (*(dest)).after = value.after;
 }
 
@@ -38,7 +44,7 @@ void assign_and_preserve_padding(device tint_array<S, 4>* const dest, tint_array
 kernel void f(device tint_array<S, 4>* tint_symbol [[buffer(1)]], const constant tint_array<S, 4>* tint_symbol_1 [[buffer(0)]]) {
   assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
-  (*(tint_symbol))[3].m = (*(tint_symbol_1))[2].m;
+  assign_and_preserve_padding_2(&((*(tint_symbol))[3].m), (*(tint_symbol_1))[2].m);
   (*(tint_symbol))[1].m[0] = half3((*(tint_symbol_1))[0].m[1]).zxy;
   return;
 }

test/tint/buffer/uniform/std140/struct/mat3x3_f16/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 147
+; Bound: 162
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
@@ -27,11 +27,14 @@
                OpMemberName %S 1 "m"
                OpMemberName %S 2 "after"
                OpName %s "s"
-               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %assign_and_preserve_padding_2_s_X_m "assign_and_preserve_padding_2_s_X_m"
                OpName %dest "dest"
                OpName %value "value"
-               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest_0 "dest"
                OpName %value_0 "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_1 "value"
                OpName %i "i"
                OpName %var_for_index "var_for_index"
                OpName %conv_S "conv_S"
@@ -84,165 +87,183 @@
        %void = OpTypeVoid
      %uint_1 = OpConstant %uint 1
 %_arr_uint_uint_1 = OpTypeArray %uint %uint_1
-         %17 = OpTypeFunction %void %_arr_uint_uint_1 %S
+         %17 = OpTypeFunction %void %_arr_uint_uint_1 %mat3v3half
      %uint_0 = OpConstant %uint 0
          %26 = OpConstantNull %int
-%_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
-%_ptr_StorageBuffer_mat3v3half = OpTypePointer StorageBuffer %mat3v3half
+%_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
+         %30 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+      %int_2 = OpConstant %int 2
      %uint_2 = OpConstant %uint 2
-         %39 = OpTypeFunction %void %_arr_S_uint_4
-         %43 = OpConstantNull %uint
+         %41 = OpTypeFunction %void %_arr_uint_uint_1 %S
+%_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
+         %57 = OpTypeFunction %void %_arr_S_uint_4
 %_ptr_Function_uint = OpTypePointer Function %uint
        %bool = OpTypeBool
 %_ptr_Function__arr_S_uint_4 = OpTypePointer Function %_arr_S_uint_4
-         %58 = OpConstantNull %_arr_S_uint_4
+         %75 = OpConstantNull %_arr_S_uint_4
 %_ptr_Function_S = OpTypePointer Function %S
-         %68 = OpTypeFunction %S %S_std140
-         %79 = OpTypeFunction %_arr_S_uint_4 %_arr_S_std140_uint_4
+         %85 = OpTypeFunction %S %S_std140
+         %96 = OpTypeFunction %_arr_S_uint_4 %_arr_S_std140_uint_4
 %_ptr_Function__arr_S_std140_uint_4 = OpTypePointer Function %_arr_S_std140_uint_4
-         %96 = OpConstantNull %_arr_S_std140_uint_4
+        %113 = OpConstantNull %_arr_S_std140_uint_4
 %_ptr_Function_S_std140 = OpTypePointer Function %S_std140
-        %107 = OpTypeFunction %mat3v3half
+        %124 = OpTypeFunction %mat3v3half
 %_ptr_Uniform_S_std140 = OpTypePointer Uniform %S_std140
 %_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
      %uint_3 = OpConstant %uint 3
-        %125 = OpTypeFunction %void
+        %142 = OpTypeFunction %void
 %_ptr_Uniform__arr_S_std140_uint_4 = OpTypePointer Uniform %_arr_S_std140_uint_4
-        %134 = OpConstantComposite %_arr_uint_uint_1 %uint_1
-      %int_3 = OpConstant %int 3
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
-%assign_and_preserve_padding_1_s_X = OpFunction %void None %17
+        %151 = OpConstantComposite %_arr_uint_uint_1 %uint_1
+        %156 = OpConstantComposite %_arr_uint_uint_1 %uint_3
+%assign_and_preserve_padding_2_s_X_m = OpFunction %void None %17
        %dest = OpFunctionParameter %_arr_uint_uint_1
-      %value = OpFunctionParameter %S
+      %value = OpFunctionParameter %mat3v3half
          %24 = OpLabel
          %27 = OpCompositeExtract %uint %dest 0
-         %29 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %27 %uint_0
-         %30 = OpCompositeExtract %int %value 0
-               OpStore %29 %30
-         %31 = OpCompositeExtract %uint %dest 0
-         %33 = OpAccessChain %_ptr_StorageBuffer_mat3v3half %s %uint_0 %31 %uint_1
-         %34 = OpCompositeExtract %mat3v3half %value 1
-               OpStore %33 %34
-         %35 = OpCompositeExtract %uint %dest 0
-         %37 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %35 %uint_2
-         %38 = OpCompositeExtract %int %value 2
-               OpStore %37 %38
+         %29 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %27 %uint_1 %26
+         %31 = OpCompositeExtract %v3half %value 0
+               OpStore %29 %31
+         %32 = OpCompositeExtract %uint %dest 0
+         %34 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %32 %uint_1 %int_1
+         %35 = OpCompositeExtract %v3half %value 1
+               OpStore %34 %35
+         %36 = OpCompositeExtract %uint %dest 0
+         %38 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %36 %uint_1 %int_2
+         %40 = OpCompositeExtract %v3half %value 2
+               OpStore %38 %40
                OpReturn
                OpFunctionEnd
-%assign_and_preserve_padding_s = OpFunction %void None %39
-    %value_0 = OpFunctionParameter %_arr_S_uint_4
-         %42 = OpLabel
-          %i = OpVariable %_ptr_Function_uint Function %43
-%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %58
-               OpStore %i %43
-               OpBranch %46
-         %46 = OpLabel
-               OpLoopMerge %47 %48 None
-               OpBranch %49
-         %49 = OpLabel
-         %51 = OpLoad %uint %i
-         %52 = OpULessThan %bool %51 %uint_4
-         %50 = OpLogicalNot %bool %52
-               OpSelectionMerge %54 None
-               OpBranchConditional %50 %55 %54
-         %55 = OpLabel
-               OpBranch %47
-         %54 = OpLabel
-               OpStore %var_for_index %value_0
-         %60 = OpLoad %uint %i
-         %61 = OpCompositeConstruct %_arr_uint_uint_1 %60
-         %62 = OpLoad %uint %i
-         %64 = OpAccessChain %_ptr_Function_S %var_for_index %62
-         %65 = OpLoad %S %64
-         %59 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %61 %65
-               OpBranch %48
-         %48 = OpLabel
-         %66 = OpLoad %uint %i
-         %67 = OpIAdd %uint %66 %uint_1
-               OpStore %i %67
-               OpBranch %46
-         %47 = OpLabel
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %41
+     %dest_0 = OpFunctionParameter %_arr_uint_uint_1
+    %value_0 = OpFunctionParameter %S
+         %45 = OpLabel
+         %46 = OpCompositeExtract %uint %dest_0 0
+         %48 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %46 %uint_0
+         %49 = OpCompositeExtract %int %value_0 0
+               OpStore %48 %49
+         %51 = OpCompositeExtract %uint %dest_0 0
+         %52 = OpCompositeConstruct %_arr_uint_uint_1 %51
+         %53 = OpCompositeExtract %mat3v3half %value_0 1
+         %50 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %52 %53
+         %54 = OpCompositeExtract %uint %dest_0 0
+         %55 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %54 %uint_2
+         %56 = OpCompositeExtract %int %value_0 2
+               OpStore %55 %56
                OpReturn
                OpFunctionEnd
-     %conv_S = OpFunction %S None %68
-        %val = OpFunctionParameter %S_std140
+%assign_and_preserve_padding_s = OpFunction %void None %57
+    %value_1 = OpFunctionParameter %_arr_S_uint_4
+         %60 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %30
+%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %75
+               OpStore %i %30
+               OpBranch %63
+         %63 = OpLabel
+               OpLoopMerge %64 %65 None
+               OpBranch %66
+         %66 = OpLabel
+         %68 = OpLoad %uint %i
+         %69 = OpULessThan %bool %68 %uint_4
+         %67 = OpLogicalNot %bool %69
+               OpSelectionMerge %71 None
+               OpBranchConditional %67 %72 %71
+         %72 = OpLabel
+               OpBranch %64
          %71 = OpLabel
-         %72 = OpCompositeExtract %int %val 0
-         %73 = OpCompositeExtract %v3half %val 1
-         %74 = OpCompositeExtract %v3half %val 2
-         %75 = OpCompositeExtract %v3half %val 3
-         %76 = OpCompositeConstruct %mat3v3half %73 %74 %75
-         %77 = OpCompositeExtract %int %val 4
-         %78 = OpCompositeConstruct %S %72 %76 %77
-               OpReturnValue %78
-               OpFunctionEnd
-%conv_arr4_S = OpFunction %_arr_S_uint_4 None %79
-      %val_0 = OpFunctionParameter %_arr_S_std140_uint_4
-         %82 = OpLabel
-        %arr = OpVariable %_ptr_Function__arr_S_uint_4 Function %58
-        %i_0 = OpVariable %_ptr_Function_uint Function %43
-%var_for_index_1 = OpVariable %_ptr_Function__arr_S_std140_uint_4 Function %96
-               OpBranch %85
-         %85 = OpLabel
-               OpLoopMerge %86 %87 None
-               OpBranch %88
-         %88 = OpLabel
-         %90 = OpLoad %uint %i_0
-         %91 = OpULessThan %bool %90 %uint_4
-         %89 = OpLogicalNot %bool %91
-               OpSelectionMerge %92 None
-               OpBranchConditional %89 %93 %92
-         %93 = OpLabel
-               OpBranch %86
-         %92 = OpLabel
-               OpStore %var_for_index_1 %val_0
-         %97 = OpLoad %uint %i_0
-         %98 = OpAccessChain %_ptr_Function_S %arr %97
-        %100 = OpLoad %uint %i_0
-        %102 = OpAccessChain %_ptr_Function_S_std140 %var_for_index_1 %100
-        %103 = OpLoad %S_std140 %102
-         %99 = OpFunctionCall %S %conv_S %103
-               OpStore %98 %99
-               OpBranch %87
-         %87 = OpLabel
-        %104 = OpLoad %uint %i_0
-        %105 = OpIAdd %uint %104 %uint_1
-               OpStore %i_0 %105
-               OpBranch %85
-         %86 = OpLabel
-        %106 = OpLoad %_arr_S_uint_4 %arr
-               OpReturnValue %106
-               OpFunctionEnd
-%load_u_inner_2_m = OpFunction %mat3v3half None %107
-        %109 = OpLabel
-        %112 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
-        %115 = OpAccessChain %_ptr_Uniform_v3half %112 %uint_1
-        %116 = OpLoad %v3half %115
-        %118 = OpAccessChain %_ptr_Uniform_v3half %112 %uint_2
-        %119 = OpLoad %v3half %118
-        %122 = OpAccessChain %_ptr_Uniform_v3half %112 %uint_3
-        %123 = OpLoad %v3half %122
-        %124 = OpCompositeConstruct %mat3v3half %116 %119 %123
-               OpReturnValue %124
-               OpFunctionEnd
-          %f = OpFunction %void None %125
-        %127 = OpLabel
-        %131 = OpAccessChain %_ptr_Uniform__arr_S_std140_uint_4 %u %uint_0
-        %132 = OpLoad %_arr_S_std140_uint_4 %131
-        %129 = OpFunctionCall %_arr_S_uint_4 %conv_arr4_S %132
-        %128 = OpFunctionCall %void %assign_and_preserve_padding_s %129
-        %136 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
-        %137 = OpLoad %S_std140 %136
-        %135 = OpFunctionCall %S %conv_S %137
-        %133 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %134 %135
-        %139 = OpAccessChain %_ptr_StorageBuffer_mat3v3half %s %uint_0 %int_3 %uint_1
-        %140 = OpFunctionCall %mat3v3half %load_u_inner_2_m
-               OpStore %139 %140
-        %143 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %uint_1 %26
-        %144 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %43 %uint_2
-        %145 = OpLoad %v3half %144
-        %146 = OpVectorShuffle %v3half %145 %145 2 0 1
-               OpStore %143 %146
+               OpStore %var_for_index %value_1
+         %77 = OpLoad %uint %i
+         %78 = OpCompositeConstruct %_arr_uint_uint_1 %77
+         %79 = OpLoad %uint %i
+         %81 = OpAccessChain %_ptr_Function_S %var_for_index %79
+         %82 = OpLoad %S %81
+         %76 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %78 %82
+               OpBranch %65
+         %65 = OpLabel
+         %83 = OpLoad %uint %i
+         %84 = OpIAdd %uint %83 %uint_1
+               OpStore %i %84
+               OpBranch %63
+         %64 = OpLabel
+               OpReturn
+               OpFunctionEnd
+     %conv_S = OpFunction %S None %85
+        %val = OpFunctionParameter %S_std140
+         %88 = OpLabel
+         %89 = OpCompositeExtract %int %val 0
+         %90 = OpCompositeExtract %v3half %val 1
+         %91 = OpCompositeExtract %v3half %val 2
+         %92 = OpCompositeExtract %v3half %val 3
+         %93 = OpCompositeConstruct %mat3v3half %90 %91 %92
+         %94 = OpCompositeExtract %int %val 4
+         %95 = OpCompositeConstruct %S %89 %93 %94
+               OpReturnValue %95
+               OpFunctionEnd
+%conv_arr4_S = OpFunction %_arr_S_uint_4 None %96
+      %val_0 = OpFunctionParameter %_arr_S_std140_uint_4
+         %99 = OpLabel
+        %arr = OpVariable %_ptr_Function__arr_S_uint_4 Function %75
+        %i_0 = OpVariable %_ptr_Function_uint Function %30
+%var_for_index_1 = OpVariable %_ptr_Function__arr_S_std140_uint_4 Function %113
+               OpBranch %102
+        %102 = OpLabel
+               OpLoopMerge %103 %104 None
+               OpBranch %105
+        %105 = OpLabel
+        %107 = OpLoad %uint %i_0
+        %108 = OpULessThan %bool %107 %uint_4
+        %106 = OpLogicalNot %bool %108
+               OpSelectionMerge %109 None
+               OpBranchConditional %106 %110 %109
+        %110 = OpLabel
+               OpBranch %103
+        %109 = OpLabel
+               OpStore %var_for_index_1 %val_0
+        %114 = OpLoad %uint %i_0
+        %115 = OpAccessChain %_ptr_Function_S %arr %114
+        %117 = OpLoad %uint %i_0
+        %119 = OpAccessChain %_ptr_Function_S_std140 %var_for_index_1 %117
+        %120 = OpLoad %S_std140 %119
+        %116 = OpFunctionCall %S %conv_S %120
+               OpStore %115 %116
+               OpBranch %104
+        %104 = OpLabel
+        %121 = OpLoad %uint %i_0
+        %122 = OpIAdd %uint %121 %uint_1
+               OpStore %i_0 %122
+               OpBranch %102
+        %103 = OpLabel
+        %123 = OpLoad %_arr_S_uint_4 %arr
+               OpReturnValue %123
+               OpFunctionEnd
+%load_u_inner_2_m = OpFunction %mat3v3half None %124
+        %126 = OpLabel
+        %129 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
+        %132 = OpAccessChain %_ptr_Uniform_v3half %129 %uint_1
+        %133 = OpLoad %v3half %132
+        %135 = OpAccessChain %_ptr_Uniform_v3half %129 %uint_2
+        %136 = OpLoad %v3half %135
+        %139 = OpAccessChain %_ptr_Uniform_v3half %129 %uint_3
+        %140 = OpLoad %v3half %139
+        %141 = OpCompositeConstruct %mat3v3half %133 %136 %140
+               OpReturnValue %141
+               OpFunctionEnd
+          %f = OpFunction %void None %142
+        %144 = OpLabel
+        %148 = OpAccessChain %_ptr_Uniform__arr_S_std140_uint_4 %u %uint_0
+        %149 = OpLoad %_arr_S_std140_uint_4 %148
+        %146 = OpFunctionCall %_arr_S_uint_4 %conv_arr4_S %149
+        %145 = OpFunctionCall %void %assign_and_preserve_padding_s %146
+        %153 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
+        %154 = OpLoad %S_std140 %153
+        %152 = OpFunctionCall %S %conv_S %154
+        %150 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %151 %152
+        %157 = OpFunctionCall %mat3v3half %load_u_inner_2_m
+        %155 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %156 %157
+        %158 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %uint_1 %26
+        %159 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %30 %uint_2
+        %160 = OpLoad %v3half %159
+        %161 = OpVectorShuffle %v3half %160 %160 2 0 1
+               OpStore %158 %161
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/struct/mat3x3_f32/to_storage.wgsl.expected.glsl

@@ -32,26 +32,34 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   S inner[4];
 } s;
 
+void assign_and_preserve_padding_2_s_X_m(uint dest[1], mat3 value) {
+  s.inner[dest[0]].m[0] = value[0u];
+  s.inner[dest[0]].m[1] = value[1u];
+  s.inner[dest[0]].m[2] = value[2u];
+}
+
 void assign_and_preserve_padding_1_s_X(uint dest[1], S value) {
   s.inner[dest[0]].before = value.before;
-  s.inner[dest[0]].m = value.m;
+  uint tint_symbol[1] = uint[1](dest[0u]);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol, value.m);
   s.inner[dest[0]].after = value.after;
 }
 
 void assign_and_preserve_padding_s(S value[4]) {
   {
     for(uint i = 0u; (i < 4u); i = (i + 1u)) {
-      uint tint_symbol[1] = uint[1](i);
-      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+      uint tint_symbol_1[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol_1, value[i]);
     }
   }
 }
 
 void f() {
   assign_and_preserve_padding_s(u.inner);
-  uint tint_symbol_1[1] = uint[1](1u);
-  assign_and_preserve_padding_1_s_X(tint_symbol_1, u.inner[2]);
-  s.inner[3].m = u.inner[2].m;
+  uint tint_symbol_2[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_2, u.inner[2]);
+  uint tint_symbol_3[1] = uint[1](3u);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol_3, u.inner[2].m);
   s.inner[1].m[0] = u.inner[0].m[1].zxy;
 }
 

test/tint/buffer/uniform/std140/struct/mat3x3_f32/to_storage.wgsl.expected.msl

@@ -22,9 +22,15 @@ struct S {
   /* 0x0044 */ tint_array<int8_t, 60> tint_pad_1;
 };
 
+void assign_and_preserve_padding_2(device float3x3* const dest, float3x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+}
+
 void assign_and_preserve_padding_1(device S* const dest, S value) {
   (*(dest)).before = value.before;
-  (*(dest)).m = value.m;
+  assign_and_preserve_padding_2(&((*(dest)).m), value.m);
   (*(dest)).after = value.after;
 }
 
@@ -37,7 +43,7 @@ void assign_and_preserve_padding(device tint_array<S, 4>* const dest, tint_array
 kernel void f(device tint_array<S, 4>* tint_symbol [[buffer(1)]], const constant tint_array<S, 4>* tint_symbol_1 [[buffer(0)]]) {
   assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
-  (*(tint_symbol))[3].m = (*(tint_symbol_1))[2].m;
+  assign_and_preserve_padding_2(&((*(tint_symbol))[3].m), (*(tint_symbol_1))[2].m);
   (*(tint_symbol))[1].m[0] = float3((*(tint_symbol_1))[0].m[1]).zxy;
   return;
 }

test/tint/buffer/uniform/std140/struct/mat3x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 90
+; Bound: 105
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -15,11 +15,14 @@
                OpMemberName %S 2 "after"
                OpName %u "u"
                OpName %s "s"
-               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %assign_and_preserve_padding_2_s_X_m "assign_and_preserve_padding_2_s_X_m"
                OpName %dest "dest"
                OpName %value "value"
-               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest_0 "dest"
                OpName %value_0 "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_1 "value"
                OpName %i "i"
                OpName %var_for_index "var_for_index"
                OpName %f "f"
@@ -53,98 +56,116 @@
        %void = OpTypeVoid
      %uint_1 = OpConstant %uint 1
 %_arr_uint_uint_1 = OpTypeArray %uint %uint_1
-         %14 = OpTypeFunction %void %_arr_uint_uint_1 %S
+         %14 = OpTypeFunction %void %_arr_uint_uint_1 %mat3v3float
      %uint_0 = OpConstant %uint 0
          %23 = OpConstantNull %int
-%_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
-%_ptr_StorageBuffer_mat3v3float = OpTypePointer StorageBuffer %mat3v3float
+%_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
+         %27 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+      %int_2 = OpConstant %int 2
      %uint_2 = OpConstant %uint 2
-         %36 = OpTypeFunction %void %_arr_S_uint_4
-         %40 = OpConstantNull %uint
+         %38 = OpTypeFunction %void %_arr_uint_uint_1 %S
+%_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
+         %54 = OpTypeFunction %void %_arr_S_uint_4
 %_ptr_Function_uint = OpTypePointer Function %uint
        %bool = OpTypeBool
 %_ptr_Function__arr_S_uint_4 = OpTypePointer Function %_arr_S_uint_4
-         %55 = OpConstantNull %_arr_S_uint_4
+         %72 = OpConstantNull %_arr_S_uint_4
 %_ptr_Function_S = OpTypePointer Function %S
-         %65 = OpTypeFunction %void
+         %82 = OpTypeFunction %void
 %_ptr_Uniform__arr_S_uint_4 = OpTypePointer Uniform %_arr_S_uint_4
-         %73 = OpConstantComposite %_arr_uint_uint_1 %uint_1
-      %int_2 = OpConstant %int 2
+         %90 = OpConstantComposite %_arr_uint_uint_1 %uint_1
 %_ptr_Uniform_S = OpTypePointer Uniform %S
-      %int_3 = OpConstant %int 3
+     %uint_3 = OpConstant %uint 3
+         %96 = OpConstantComposite %_arr_uint_uint_1 %uint_3
 %_ptr_Uniform_mat3v3float = OpTypePointer Uniform %mat3v3float
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
-%assign_and_preserve_padding_1_s_X = OpFunction %void None %14
+%assign_and_preserve_padding_2_s_X_m = OpFunction %void None %14
        %dest = OpFunctionParameter %_arr_uint_uint_1
-      %value = OpFunctionParameter %S
+      %value = OpFunctionParameter %mat3v3float
          %21 = OpLabel
          %24 = OpCompositeExtract %uint %dest 0
-         %26 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %24 %uint_0
-         %27 = OpCompositeExtract %int %value 0
-               OpStore %26 %27
-         %28 = OpCompositeExtract %uint %dest 0
-         %30 = OpAccessChain %_ptr_StorageBuffer_mat3v3float %s %uint_0 %28 %uint_1
-         %31 = OpCompositeExtract %mat3v3float %value 1
-               OpStore %30 %31
-         %32 = OpCompositeExtract %uint %dest 0
-         %34 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %32 %uint_2
-         %35 = OpCompositeExtract %int %value 2
-               OpStore %34 %35
+         %26 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %24 %uint_1 %23
+         %28 = OpCompositeExtract %v3float %value 0
+               OpStore %26 %28
+         %29 = OpCompositeExtract %uint %dest 0
+         %31 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %29 %uint_1 %int_1
+         %32 = OpCompositeExtract %v3float %value 1
+               OpStore %31 %32
+         %33 = OpCompositeExtract %uint %dest 0
+         %35 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %33 %uint_1 %int_2
+         %37 = OpCompositeExtract %v3float %value 2
+               OpStore %35 %37
                OpReturn
                OpFunctionEnd
-%assign_and_preserve_padding_s = OpFunction %void None %36
-    %value_0 = OpFunctionParameter %_arr_S_uint_4
-         %39 = OpLabel
-          %i = OpVariable %_ptr_Function_uint Function %40
-%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %55
-               OpStore %i %40
-               OpBranch %43
-         %43 = OpLabel
-               OpLoopMerge %44 %45 None
-               OpBranch %46
-         %46 = OpLabel
-         %48 = OpLoad %uint %i
-         %49 = OpULessThan %bool %48 %uint_4
-         %47 = OpLogicalNot %bool %49
-               OpSelectionMerge %51 None
-               OpBranchConditional %47 %52 %51
-         %52 = OpLabel
-               OpBranch %44
-         %51 = OpLabel
-               OpStore %var_for_index %value_0
-         %57 = OpLoad %uint %i
-         %58 = OpCompositeConstruct %_arr_uint_uint_1 %57
-         %59 = OpLoad %uint %i
-         %61 = OpAccessChain %_ptr_Function_S %var_for_index %59
-         %62 = OpLoad %S %61
-         %56 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %58 %62
-               OpBranch %45
-         %45 = OpLabel
-         %63 = OpLoad %uint %i
-         %64 = OpIAdd %uint %63 %uint_1
-               OpStore %i %64
-               OpBranch %43
-         %44 = OpLabel
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %38
+     %dest_0 = OpFunctionParameter %_arr_uint_uint_1
+    %value_0 = OpFunctionParameter %S
+         %42 = OpLabel
+         %43 = OpCompositeExtract %uint %dest_0 0
+         %45 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %43 %uint_0
+         %46 = OpCompositeExtract %int %value_0 0
+               OpStore %45 %46
+         %48 = OpCompositeExtract %uint %dest_0 0
+         %49 = OpCompositeConstruct %_arr_uint_uint_1 %48
+         %50 = OpCompositeExtract %mat3v3float %value_0 1
+         %47 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %49 %50
+         %51 = OpCompositeExtract %uint %dest_0 0
+         %52 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %51 %uint_2
+         %53 = OpCompositeExtract %int %value_0 2
+               OpStore %52 %53
                OpReturn
                OpFunctionEnd
-          %f = OpFunction %void None %65
-         %67 = OpLabel
-         %70 = OpAccessChain %_ptr_Uniform__arr_S_uint_4 %u %uint_0
-         %71 = OpLoad %_arr_S_uint_4 %70
-         %68 = OpFunctionCall %void %assign_and_preserve_padding_s %71
-         %76 = OpAccessChain %_ptr_Uniform_S %u %uint_0 %int_2
-         %77 = OpLoad %S %76
-         %72 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %73 %77
-         %79 = OpAccessChain %_ptr_StorageBuffer_mat3v3float %s %uint_0 %int_3 %uint_1
-         %81 = OpAccessChain %_ptr_Uniform_mat3v3float %u %uint_0 %int_2 %uint_1
-         %82 = OpLoad %mat3v3float %81
-               OpStore %79 %82
-         %85 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %uint_1 %23
-         %87 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %23 %uint_1 %int_1
-         %88 = OpLoad %v3float %87
-         %89 = OpVectorShuffle %v3float %88 %88 2 0 1
-               OpStore %85 %89
+%assign_and_preserve_padding_s = OpFunction %void None %54
+    %value_1 = OpFunctionParameter %_arr_S_uint_4
+         %57 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %27
+%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %72
+               OpStore %i %27
+               OpBranch %60
+         %60 = OpLabel
+               OpLoopMerge %61 %62 None
+               OpBranch %63
+         %63 = OpLabel
+         %65 = OpLoad %uint %i
+         %66 = OpULessThan %bool %65 %uint_4
+         %64 = OpLogicalNot %bool %66
+               OpSelectionMerge %68 None
+               OpBranchConditional %64 %69 %68
+         %69 = OpLabel
+               OpBranch %61
+         %68 = OpLabel
+               OpStore %var_for_index %value_1
+         %74 = OpLoad %uint %i
+         %75 = OpCompositeConstruct %_arr_uint_uint_1 %74
+         %76 = OpLoad %uint %i
+         %78 = OpAccessChain %_ptr_Function_S %var_for_index %76
+         %79 = OpLoad %S %78
+         %73 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %75 %79
+               OpBranch %62
+         %62 = OpLabel
+         %80 = OpLoad %uint %i
+         %81 = OpIAdd %uint %80 %uint_1
+               OpStore %i %81
+               OpBranch %60
+         %61 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %82
+         %84 = OpLabel
+         %87 = OpAccessChain %_ptr_Uniform__arr_S_uint_4 %u %uint_0
+         %88 = OpLoad %_arr_S_uint_4 %87
+         %85 = OpFunctionCall %void %assign_and_preserve_padding_s %88
+         %92 = OpAccessChain %_ptr_Uniform_S %u %uint_0 %int_2
+         %93 = OpLoad %S %92
+         %89 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %90 %93
+         %98 = OpAccessChain %_ptr_Uniform_mat3v3float %u %uint_0 %int_2 %uint_1
+         %99 = OpLoad %mat3v3float %98
+         %94 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %96 %99
+        %100 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %uint_1 %23
+        %102 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %23 %uint_1 %int_1
+        %103 = OpLoad %v3float %102
+        %104 = OpVectorShuffle %v3float %103 %103 2 0 1
+               OpStore %100 %104
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/struct/mat4x3_f16/to_storage.wgsl.expected.glsl

@@ -68,17 +68,25 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   S inner[4];
 } s;
 
+void assign_and_preserve_padding_2_s_X_m(uint dest[1], f16mat4x3 value) {
+  s.inner[dest[0]].m[0] = value[0u];
+  s.inner[dest[0]].m[1] = value[1u];
+  s.inner[dest[0]].m[2] = value[2u];
+  s.inner[dest[0]].m[3] = value[3u];
+}
+
 void assign_and_preserve_padding_1_s_X(uint dest[1], S value) {
   s.inner[dest[0]].before = value.before;
-  s.inner[dest[0]].m = value.m;
+  uint tint_symbol[1] = uint[1](dest[0u]);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol, value.m);
   s.inner[dest[0]].after = value.after;
 }
 
 void assign_and_preserve_padding_s(S value[4]) {
   {
     for(uint i = 0u; (i < 4u); i = (i + 1u)) {
-      uint tint_symbol[1] = uint[1](i);
-      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+      uint tint_symbol_1[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol_1, value[i]);
     }
   }
 }
@@ -103,9 +111,10 @@ f16mat4x3 load_u_inner_2_m() {
 
 void f() {
   assign_and_preserve_padding_s(conv_arr4_S(u.inner));
-  uint tint_symbol_1[1] = uint[1](1u);
-  assign_and_preserve_padding_1_s_X(tint_symbol_1, conv_S(u.inner[2u]));
-  s.inner[3].m = load_u_inner_2_m();
+  uint tint_symbol_2[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_2, conv_S(u.inner[2u]));
+  uint tint_symbol_3[1] = uint[1](3u);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol_3, load_u_inner_2_m());
   s.inner[1].m[0] = u.inner[0u].m_1.zxy;
 }
 

test/tint/buffer/uniform/std140/struct/mat4x3_f16/to_storage.wgsl.expected.msl

@@ -23,9 +23,16 @@ struct S {
   /* 0x0044 */ tint_array<int8_t, 60> tint_pad_2;
 };
 
+void assign_and_preserve_padding_2(device half4x3* const dest, half4x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+  (*(dest))[3u] = value[3u];
+}
+
 void assign_and_preserve_padding_1(device S* const dest, S value) {
   (*(dest)).before = value.before;
-  (*(dest)).m = value.m;
+  assign_and_preserve_padding_2(&((*(dest)).m), value.m);
   (*(dest)).after = value.after;
 }
 
@@ -38,7 +45,7 @@ void assign_and_preserve_padding(device tint_array<S, 4>* const dest, tint_array
 kernel void f(device tint_array<S, 4>* tint_symbol [[buffer(1)]], const constant tint_array<S, 4>* tint_symbol_1 [[buffer(0)]]) {
   assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
-  (*(tint_symbol))[3].m = (*(tint_symbol_1))[2].m;
+  assign_and_preserve_padding_2(&((*(tint_symbol))[3].m), (*(tint_symbol_1))[2].m);
   (*(tint_symbol))[1].m[0] = half3((*(tint_symbol_1))[0].m[1]).zxy;
   return;
 }

test/tint/buffer/uniform/std140/struct/mat4x3_f16/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 151
+; Bound: 170
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
@@ -28,11 +28,14 @@
                OpMemberName %S 1 "m"
                OpMemberName %S 2 "after"
                OpName %s "s"
-               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %assign_and_preserve_padding_2_s_X_m "assign_and_preserve_padding_2_s_X_m"
                OpName %dest "dest"
                OpName %value "value"
-               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest_0 "dest"
                OpName %value_0 "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_1 "value"
                OpName %i "i"
                OpName %var_for_index "var_for_index"
                OpName %conv_S "conv_S"
@@ -86,168 +89,191 @@
        %void = OpTypeVoid
      %uint_1 = OpConstant %uint 1
 %_arr_uint_uint_1 = OpTypeArray %uint %uint_1
-         %17 = OpTypeFunction %void %_arr_uint_uint_1 %S
+         %17 = OpTypeFunction %void %_arr_uint_uint_1 %mat4v3half
      %uint_0 = OpConstant %uint 0
          %26 = OpConstantNull %int
-%_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
-%_ptr_StorageBuffer_mat4v3half = OpTypePointer StorageBuffer %mat4v3half
+%_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
+         %30 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+      %int_2 = OpConstant %int 2
      %uint_2 = OpConstant %uint 2
-         %39 = OpTypeFunction %void %_arr_S_uint_4
-         %43 = OpConstantNull %uint
+      %int_3 = OpConstant %int 3
+     %uint_3 = OpConstant %uint 3
+         %46 = OpTypeFunction %void %_arr_uint_uint_1 %S
+%_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
+         %62 = OpTypeFunction %void %_arr_S_uint_4
 %_ptr_Function_uint = OpTypePointer Function %uint
        %bool = OpTypeBool
 %_ptr_Function__arr_S_uint_4 = OpTypePointer Function %_arr_S_uint_4
-         %58 = OpConstantNull %_arr_S_uint_4
+         %80 = OpConstantNull %_arr_S_uint_4
 %_ptr_Function_S = OpTypePointer Function %S
-         %68 = OpTypeFunction %S %S_std140
-         %80 = OpTypeFunction %_arr_S_uint_4 %_arr_S_std140_uint_4
+         %90 = OpTypeFunction %S %S_std140
+        %102 = OpTypeFunction %_arr_S_uint_4 %_arr_S_std140_uint_4
 %_ptr_Function__arr_S_std140_uint_4 = OpTypePointer Function %_arr_S_std140_uint_4
-         %97 = OpConstantNull %_arr_S_std140_uint_4
+        %119 = OpConstantNull %_arr_S_std140_uint_4
 %_ptr_Function_S_std140 = OpTypePointer Function %S_std140
-        %108 = OpTypeFunction %mat4v3half
+        %130 = OpTypeFunction %mat4v3half
 %_ptr_Uniform_S_std140 = OpTypePointer Uniform %S_std140
 %_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
-     %uint_3 = OpConstant %uint 3
-        %129 = OpTypeFunction %void
+        %150 = OpTypeFunction %void
 %_ptr_Uniform__arr_S_std140_uint_4 = OpTypePointer Uniform %_arr_S_std140_uint_4
-        %138 = OpConstantComposite %_arr_uint_uint_1 %uint_1
-      %int_3 = OpConstant %int 3
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
-%assign_and_preserve_padding_1_s_X = OpFunction %void None %17
+        %159 = OpConstantComposite %_arr_uint_uint_1 %uint_1
+        %164 = OpConstantComposite %_arr_uint_uint_1 %uint_3
+%assign_and_preserve_padding_2_s_X_m = OpFunction %void None %17
        %dest = OpFunctionParameter %_arr_uint_uint_1
-      %value = OpFunctionParameter %S
+      %value = OpFunctionParameter %mat4v3half
          %24 = OpLabel
          %27 = OpCompositeExtract %uint %dest 0
-         %29 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %27 %uint_0
-         %30 = OpCompositeExtract %int %value 0
-               OpStore %29 %30
-         %31 = OpCompositeExtract %uint %dest 0
-         %33 = OpAccessChain %_ptr_StorageBuffer_mat4v3half %s %uint_0 %31 %uint_1
-         %34 = OpCompositeExtract %mat4v3half %value 1
-               OpStore %33 %34
-         %35 = OpCompositeExtract %uint %dest 0
-         %37 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %35 %uint_2
-         %38 = OpCompositeExtract %int %value 2
-               OpStore %37 %38
+         %29 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %27 %uint_1 %26
+         %31 = OpCompositeExtract %v3half %value 0
+               OpStore %29 %31
+         %32 = OpCompositeExtract %uint %dest 0
+         %34 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %32 %uint_1 %int_1
+         %35 = OpCompositeExtract %v3half %value 1
+               OpStore %34 %35
+         %36 = OpCompositeExtract %uint %dest 0
+         %38 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %36 %uint_1 %int_2
+         %40 = OpCompositeExtract %v3half %value 2
+               OpStore %38 %40
+         %41 = OpCompositeExtract %uint %dest 0
+         %43 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %41 %uint_1 %int_3
+         %45 = OpCompositeExtract %v3half %value 3
+               OpStore %43 %45
                OpReturn
                OpFunctionEnd
-%assign_and_preserve_padding_s = OpFunction %void None %39
-    %value_0 = OpFunctionParameter %_arr_S_uint_4
-         %42 = OpLabel
-          %i = OpVariable %_ptr_Function_uint Function %43
-%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %58
-               OpStore %i %43
-               OpBranch %46
-         %46 = OpLabel
-               OpLoopMerge %47 %48 None
-               OpBranch %49
-         %49 = OpLabel
-         %51 = OpLoad %uint %i
-         %52 = OpULessThan %bool %51 %uint_4
-         %50 = OpLogicalNot %bool %52
-               OpSelectionMerge %54 None
-               OpBranchConditional %50 %55 %54
-         %55 = OpLabel
-               OpBranch %47
-         %54 = OpLabel
-               OpStore %var_for_index %value_0
-         %60 = OpLoad %uint %i
-         %61 = OpCompositeConstruct %_arr_uint_uint_1 %60
-         %62 = OpLoad %uint %i
-         %64 = OpAccessChain %_ptr_Function_S %var_for_index %62
-         %65 = OpLoad %S %64
-         %59 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %61 %65
-               OpBranch %48
-         %48 = OpLabel
-         %66 = OpLoad %uint %i
-         %67 = OpIAdd %uint %66 %uint_1
-               OpStore %i %67
-               OpBranch %46
-         %47 = OpLabel
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %46
+     %dest_0 = OpFunctionParameter %_arr_uint_uint_1
+    %value_0 = OpFunctionParameter %S
+         %50 = OpLabel
+         %51 = OpCompositeExtract %uint %dest_0 0
+         %53 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %51 %uint_0
+         %54 = OpCompositeExtract %int %value_0 0
+               OpStore %53 %54
+         %56 = OpCompositeExtract %uint %dest_0 0
+         %57 = OpCompositeConstruct %_arr_uint_uint_1 %56
+         %58 = OpCompositeExtract %mat4v3half %value_0 1
+         %55 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %57 %58
+         %59 = OpCompositeExtract %uint %dest_0 0
+         %60 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %59 %uint_2
+         %61 = OpCompositeExtract %int %value_0 2
+               OpStore %60 %61
                OpReturn
                OpFunctionEnd
-     %conv_S = OpFunction %S None %68
-        %val = OpFunctionParameter %S_std140
+%assign_and_preserve_padding_s = OpFunction %void None %62
+    %value_1 = OpFunctionParameter %_arr_S_uint_4
+         %65 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %30
+%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %80
+               OpStore %i %30
+               OpBranch %68
+         %68 = OpLabel
+               OpLoopMerge %69 %70 None
+               OpBranch %71
          %71 = OpLabel
-         %72 = OpCompositeExtract %int %val 0
-         %73 = OpCompositeExtract %v3half %val 1
-         %74 = OpCompositeExtract %v3half %val 2
-         %75 = OpCompositeExtract %v3half %val 3
-         %76 = OpCompositeExtract %v3half %val 4
-         %77 = OpCompositeConstruct %mat4v3half %73 %74 %75 %76
-         %78 = OpCompositeExtract %int %val 5
-         %79 = OpCompositeConstruct %S %72 %77 %78
-               OpReturnValue %79
-               OpFunctionEnd
-%conv_arr4_S = OpFunction %_arr_S_uint_4 None %80
-      %val_0 = OpFunctionParameter %_arr_S_std140_uint_4
-         %83 = OpLabel
-        %arr = OpVariable %_ptr_Function__arr_S_uint_4 Function %58
-        %i_0 = OpVariable %_ptr_Function_uint Function %43
-%var_for_index_1 = OpVariable %_ptr_Function__arr_S_std140_uint_4 Function %97
-               OpBranch %86
-         %86 = OpLabel
-               OpLoopMerge %87 %88 None
-               OpBranch %89
-         %89 = OpLabel
-         %91 = OpLoad %uint %i_0
-         %92 = OpULessThan %bool %91 %uint_4
-         %90 = OpLogicalNot %bool %92
-               OpSelectionMerge %93 None
-               OpBranchConditional %90 %94 %93
-         %94 = OpLabel
-               OpBranch %87
-         %93 = OpLabel
-               OpStore %var_for_index_1 %val_0
-         %98 = OpLoad %uint %i_0
-         %99 = OpAccessChain %_ptr_Function_S %arr %98
-        %101 = OpLoad %uint %i_0
-        %103 = OpAccessChain %_ptr_Function_S_std140 %var_for_index_1 %101
-        %104 = OpLoad %S_std140 %103
-        %100 = OpFunctionCall %S %conv_S %104
-               OpStore %99 %100
-               OpBranch %88
-         %88 = OpLabel
-        %105 = OpLoad %uint %i_0
-        %106 = OpIAdd %uint %105 %uint_1
-               OpStore %i_0 %106
-               OpBranch %86
-         %87 = OpLabel
-        %107 = OpLoad %_arr_S_uint_4 %arr
-               OpReturnValue %107
-               OpFunctionEnd
-%load_u_inner_2_m = OpFunction %mat4v3half None %108
-        %110 = OpLabel
-        %113 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
-        %116 = OpAccessChain %_ptr_Uniform_v3half %113 %uint_1
-        %117 = OpLoad %v3half %116
-        %119 = OpAccessChain %_ptr_Uniform_v3half %113 %uint_2
-        %120 = OpLoad %v3half %119
-        %123 = OpAccessChain %_ptr_Uniform_v3half %113 %uint_3
-        %124 = OpLoad %v3half %123
-        %126 = OpAccessChain %_ptr_Uniform_v3half %113 %uint_4
-        %127 = OpLoad %v3half %126
-        %128 = OpCompositeConstruct %mat4v3half %117 %120 %124 %127
-               OpReturnValue %128
-               OpFunctionEnd
-          %f = OpFunction %void None %129
-        %131 = OpLabel
-        %135 = OpAccessChain %_ptr_Uniform__arr_S_std140_uint_4 %u %uint_0
-        %136 = OpLoad %_arr_S_std140_uint_4 %135
-        %133 = OpFunctionCall %_arr_S_uint_4 %conv_arr4_S %136
-        %132 = OpFunctionCall %void %assign_and_preserve_padding_s %133
-        %140 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
-        %141 = OpLoad %S_std140 %140
-        %139 = OpFunctionCall %S %conv_S %141
-        %137 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %138 %139
-        %143 = OpAccessChain %_ptr_StorageBuffer_mat4v3half %s %uint_0 %int_3 %uint_1
-        %144 = OpFunctionCall %mat4v3half %load_u_inner_2_m
-               OpStore %143 %144
-        %147 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %uint_1 %26
-        %148 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %43 %uint_2
-        %149 = OpLoad %v3half %148
-        %150 = OpVectorShuffle %v3half %149 %149 2 0 1
-               OpStore %147 %150
+         %73 = OpLoad %uint %i
+         %74 = OpULessThan %bool %73 %uint_4
+         %72 = OpLogicalNot %bool %74
+               OpSelectionMerge %76 None
+               OpBranchConditional %72 %77 %76
+         %77 = OpLabel
+               OpBranch %69
+         %76 = OpLabel
+               OpStore %var_for_index %value_1
+         %82 = OpLoad %uint %i
+         %83 = OpCompositeConstruct %_arr_uint_uint_1 %82
+         %84 = OpLoad %uint %i
+         %86 = OpAccessChain %_ptr_Function_S %var_for_index %84
+         %87 = OpLoad %S %86
+         %81 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %83 %87
+               OpBranch %70
+         %70 = OpLabel
+         %88 = OpLoad %uint %i
+         %89 = OpIAdd %uint %88 %uint_1
+               OpStore %i %89
+               OpBranch %68
+         %69 = OpLabel
+               OpReturn
+               OpFunctionEnd
+     %conv_S = OpFunction %S None %90
+        %val = OpFunctionParameter %S_std140
+         %93 = OpLabel
+         %94 = OpCompositeExtract %int %val 0
+         %95 = OpCompositeExtract %v3half %val 1
+         %96 = OpCompositeExtract %v3half %val 2
+         %97 = OpCompositeExtract %v3half %val 3
+         %98 = OpCompositeExtract %v3half %val 4
+         %99 = OpCompositeConstruct %mat4v3half %95 %96 %97 %98
+        %100 = OpCompositeExtract %int %val 5
+        %101 = OpCompositeConstruct %S %94 %99 %100
+               OpReturnValue %101
+               OpFunctionEnd
+%conv_arr4_S = OpFunction %_arr_S_uint_4 None %102
+      %val_0 = OpFunctionParameter %_arr_S_std140_uint_4
+        %105 = OpLabel
+        %arr = OpVariable %_ptr_Function__arr_S_uint_4 Function %80
+        %i_0 = OpVariable %_ptr_Function_uint Function %30
+%var_for_index_1 = OpVariable %_ptr_Function__arr_S_std140_uint_4 Function %119
+               OpBranch %108
+        %108 = OpLabel
+               OpLoopMerge %109 %110 None
+               OpBranch %111
+        %111 = OpLabel
+        %113 = OpLoad %uint %i_0
+        %114 = OpULessThan %bool %113 %uint_4
+        %112 = OpLogicalNot %bool %114
+               OpSelectionMerge %115 None
+               OpBranchConditional %112 %116 %115
+        %116 = OpLabel
+               OpBranch %109
+        %115 = OpLabel
+               OpStore %var_for_index_1 %val_0
+        %120 = OpLoad %uint %i_0
+        %121 = OpAccessChain %_ptr_Function_S %arr %120
+        %123 = OpLoad %uint %i_0
+        %125 = OpAccessChain %_ptr_Function_S_std140 %var_for_index_1 %123
+        %126 = OpLoad %S_std140 %125
+        %122 = OpFunctionCall %S %conv_S %126
+               OpStore %121 %122
+               OpBranch %110
+        %110 = OpLabel
+        %127 = OpLoad %uint %i_0
+        %128 = OpIAdd %uint %127 %uint_1
+               OpStore %i_0 %128
+               OpBranch %108
+        %109 = OpLabel
+        %129 = OpLoad %_arr_S_uint_4 %arr
+               OpReturnValue %129
+               OpFunctionEnd
+%load_u_inner_2_m = OpFunction %mat4v3half None %130
+        %132 = OpLabel
+        %135 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
+        %138 = OpAccessChain %_ptr_Uniform_v3half %135 %uint_1
+        %139 = OpLoad %v3half %138
+        %141 = OpAccessChain %_ptr_Uniform_v3half %135 %uint_2
+        %142 = OpLoad %v3half %141
+        %144 = OpAccessChain %_ptr_Uniform_v3half %135 %uint_3
+        %145 = OpLoad %v3half %144
+        %147 = OpAccessChain %_ptr_Uniform_v3half %135 %uint_4
+        %148 = OpLoad %v3half %147
+        %149 = OpCompositeConstruct %mat4v3half %139 %142 %145 %148
+               OpReturnValue %149
+               OpFunctionEnd
+          %f = OpFunction %void None %150
+        %152 = OpLabel
+        %156 = OpAccessChain %_ptr_Uniform__arr_S_std140_uint_4 %u %uint_0
+        %157 = OpLoad %_arr_S_std140_uint_4 %156
+        %154 = OpFunctionCall %_arr_S_uint_4 %conv_arr4_S %157
+        %153 = OpFunctionCall %void %assign_and_preserve_padding_s %154
+        %161 = OpAccessChain %_ptr_Uniform_S_std140 %u %uint_0 %uint_2
+        %162 = OpLoad %S_std140 %161
+        %160 = OpFunctionCall %S %conv_S %162
+        %158 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %159 %160
+        %165 = OpFunctionCall %mat4v3half %load_u_inner_2_m
+        %163 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %164 %165
+        %166 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1 %uint_1 %26
+        %167 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0 %30 %uint_2
+        %168 = OpLoad %v3half %167
+        %169 = OpVectorShuffle %v3half %168 %168 2 0 1
+               OpStore %166 %169
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/struct/mat4x3_f32/to_storage.wgsl.expected.glsl

@@ -44,26 +44,35 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   S inner[4];
 } s;
 
+void assign_and_preserve_padding_2_s_X_m(uint dest[1], mat4x3 value) {
+  s.inner[dest[0]].m[0] = value[0u];
+  s.inner[dest[0]].m[1] = value[1u];
+  s.inner[dest[0]].m[2] = value[2u];
+  s.inner[dest[0]].m[3] = value[3u];
+}
+
 void assign_and_preserve_padding_1_s_X(uint dest[1], S value) {
   s.inner[dest[0]].before = value.before;
-  s.inner[dest[0]].m = value.m;
+  uint tint_symbol[1] = uint[1](dest[0u]);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol, value.m);
   s.inner[dest[0]].after = value.after;
 }
 
 void assign_and_preserve_padding_s(S value[4]) {
   {
     for(uint i = 0u; (i < 4u); i = (i + 1u)) {
-      uint tint_symbol[1] = uint[1](i);
-      assign_and_preserve_padding_1_s_X(tint_symbol, value[i]);
+      uint tint_symbol_1[1] = uint[1](i);
+      assign_and_preserve_padding_1_s_X(tint_symbol_1, value[i]);
     }
   }
 }
 
 void f() {
   assign_and_preserve_padding_s(u.inner);
-  uint tint_symbol_1[1] = uint[1](1u);
-  assign_and_preserve_padding_1_s_X(tint_symbol_1, u.inner[2]);
-  s.inner[3].m = u.inner[2].m;
+  uint tint_symbol_2[1] = uint[1](1u);
+  assign_and_preserve_padding_1_s_X(tint_symbol_2, u.inner[2]);
+  uint tint_symbol_3[1] = uint[1](3u);
+  assign_and_preserve_padding_2_s_X_m(tint_symbol_3, u.inner[2].m);
   s.inner[1].m[0] = u.inner[0].m[1].zxy;
 }
 

test/tint/buffer/uniform/std140/struct/mat4x3_f32/to_storage.wgsl.expected.msl

@@ -23,9 +23,16 @@ struct S {
   /* 0x0084 */ tint_array<int8_t, 60> tint_pad_2;
 };
 
+void assign_and_preserve_padding_2(device float4x3* const dest, float4x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+  (*(dest))[3u] = value[3u];
+}
+
 void assign_and_preserve_padding_1(device S* const dest, S value) {
   (*(dest)).before = value.before;
-  (*(dest)).m = value.m;
+  assign_and_preserve_padding_2(&((*(dest)).m), value.m);
   (*(dest)).after = value.after;
 }
 
@@ -38,7 +45,7 @@ void assign_and_preserve_padding(device tint_array<S, 4>* const dest, tint_array
 kernel void f(device tint_array<S, 4>* tint_symbol [[buffer(1)]], const constant tint_array<S, 4>* tint_symbol_1 [[buffer(0)]]) {
   assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   assign_and_preserve_padding_1(&((*(tint_symbol))[1]), (*(tint_symbol_1))[2]);
-  (*(tint_symbol))[3].m = (*(tint_symbol_1))[2].m;
+  assign_and_preserve_padding_2(&((*(tint_symbol))[3].m), (*(tint_symbol_1))[2].m);
   (*(tint_symbol))[1].m[0] = float3((*(tint_symbol_1))[0].m[1]).zxy;
   return;
 }

test/tint/buffer/uniform/std140/struct/mat4x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 90
+; Bound: 109
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -15,11 +15,14 @@
                OpMemberName %S 2 "after"
                OpName %u "u"
                OpName %s "s"
-               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %assign_and_preserve_padding_2_s_X_m "assign_and_preserve_padding_2_s_X_m"
                OpName %dest "dest"
                OpName %value "value"
-               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %assign_and_preserve_padding_1_s_X "assign_and_preserve_padding_1_s_X"
+               OpName %dest_0 "dest"
                OpName %value_0 "value"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value_1 "value"
                OpName %i "i"
                OpName %var_for_index "var_for_index"
                OpName %f "f"
@@ -53,98 +56,121 @@
        %void = OpTypeVoid
      %uint_1 = OpConstant %uint 1
 %_arr_uint_uint_1 = OpTypeArray %uint %uint_1
-         %14 = OpTypeFunction %void %_arr_uint_uint_1 %S
+         %14 = OpTypeFunction %void %_arr_uint_uint_1 %mat4v3float
      %uint_0 = OpConstant %uint 0
          %23 = OpConstantNull %int
-%_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
-%_ptr_StorageBuffer_mat4v3float = OpTypePointer StorageBuffer %mat4v3float
+%_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
+         %27 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+      %int_2 = OpConstant %int 2
      %uint_2 = OpConstant %uint 2
-         %36 = OpTypeFunction %void %_arr_S_uint_4
-         %40 = OpConstantNull %uint
+      %int_3 = OpConstant %int 3
+     %uint_3 = OpConstant %uint 3
+         %43 = OpTypeFunction %void %_arr_uint_uint_1 %S
+%_ptr_StorageBuffer_int = OpTypePointer StorageBuffer %int
+         %59 = OpTypeFunction %void %_arr_S_uint_4
 %_ptr_Function_uint = OpTypePointer Function %uint
        %bool = OpTypeBool
 %_ptr_Function__arr_S_uint_4 = OpTypePointer Function %_arr_S_uint_4
-         %55 = OpConstantNull %_arr_S_uint_4
+         %77 = OpConstantNull %_arr_S_uint_4
 %_ptr_Function_S = OpTypePointer Function %S
-         %65 = OpTypeFunction %void
+         %87 = OpTypeFunction %void
 %_ptr_Uniform__arr_S_uint_4 = OpTypePointer Uniform %_arr_S_uint_4
-         %73 = OpConstantComposite %_arr_uint_uint_1 %uint_1
-      %int_2 = OpConstant %int 2
+         %95 = OpConstantComposite %_arr_uint_uint_1 %uint_1
 %_ptr_Uniform_S = OpTypePointer Uniform %S
-      %int_3 = OpConstant %int 3
+        %100 = OpConstantComposite %_arr_uint_uint_1 %uint_3
 %_ptr_Uniform_mat4v3float = OpTypePointer Uniform %mat4v3float
-      %int_1 = OpConstant %int 1
-%_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
-%assign_and_preserve_padding_1_s_X = OpFunction %void None %14
+%assign_and_preserve_padding_2_s_X_m = OpFunction %void None %14
        %dest = OpFunctionParameter %_arr_uint_uint_1
-      %value = OpFunctionParameter %S
+      %value = OpFunctionParameter %mat4v3float
          %21 = OpLabel
          %24 = OpCompositeExtract %uint %dest 0
-         %26 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %24 %uint_0
-         %27 = OpCompositeExtract %int %value 0
-               OpStore %26 %27
-         %28 = OpCompositeExtract %uint %dest 0
-         %30 = OpAccessChain %_ptr_StorageBuffer_mat4v3float %s %uint_0 %28 %uint_1
-         %31 = OpCompositeExtract %mat4v3float %value 1
-               OpStore %30 %31
-         %32 = OpCompositeExtract %uint %dest 0
-         %34 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %32 %uint_2
-         %35 = OpCompositeExtract %int %value 2
-               OpStore %34 %35
+         %26 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %24 %uint_1 %23
+         %28 = OpCompositeExtract %v3float %value 0
+               OpStore %26 %28
+         %29 = OpCompositeExtract %uint %dest 0
+         %31 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %29 %uint_1 %int_1
+         %32 = OpCompositeExtract %v3float %value 1
+               OpStore %31 %32
+         %33 = OpCompositeExtract %uint %dest 0
+         %35 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %33 %uint_1 %int_2
+         %37 = OpCompositeExtract %v3float %value 2
+               OpStore %35 %37
+         %38 = OpCompositeExtract %uint %dest 0
+         %40 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %38 %uint_1 %int_3
+         %42 = OpCompositeExtract %v3float %value 3
+               OpStore %40 %42
                OpReturn
                OpFunctionEnd
-%assign_and_preserve_padding_s = OpFunction %void None %36
-    %value_0 = OpFunctionParameter %_arr_S_uint_4
-         %39 = OpLabel
-          %i = OpVariable %_ptr_Function_uint Function %40
-%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %55
-               OpStore %i %40
-               OpBranch %43
-         %43 = OpLabel
-               OpLoopMerge %44 %45 None
-               OpBranch %46
-         %46 = OpLabel
-         %48 = OpLoad %uint %i
-         %49 = OpULessThan %bool %48 %uint_4
-         %47 = OpLogicalNot %bool %49
-               OpSelectionMerge %51 None
-               OpBranchConditional %47 %52 %51
-         %52 = OpLabel
-               OpBranch %44
-         %51 = OpLabel
-               OpStore %var_for_index %value_0
-         %57 = OpLoad %uint %i
-         %58 = OpCompositeConstruct %_arr_uint_uint_1 %57
-         %59 = OpLoad %uint %i
-         %61 = OpAccessChain %_ptr_Function_S %var_for_index %59
-         %62 = OpLoad %S %61
-         %56 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %58 %62
-               OpBranch %45
-         %45 = OpLabel
-         %63 = OpLoad %uint %i
-         %64 = OpIAdd %uint %63 %uint_1
-               OpStore %i %64
-               OpBranch %43
-         %44 = OpLabel
+%assign_and_preserve_padding_1_s_X = OpFunction %void None %43
+     %dest_0 = OpFunctionParameter %_arr_uint_uint_1
+    %value_0 = OpFunctionParameter %S
+         %47 = OpLabel
+         %48 = OpCompositeExtract %uint %dest_0 0
+         %50 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %48 %uint_0
+         %51 = OpCompositeExtract %int %value_0 0
+               OpStore %50 %51
+         %53 = OpCompositeExtract %uint %dest_0 0
+         %54 = OpCompositeConstruct %_arr_uint_uint_1 %53
+         %55 = OpCompositeExtract %mat4v3float %value_0 1
+         %52 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %54 %55
+         %56 = OpCompositeExtract %uint %dest_0 0
+         %57 = OpAccessChain %_ptr_StorageBuffer_int %s %uint_0 %56 %uint_2
+         %58 = OpCompositeExtract %int %value_0 2
+               OpStore %57 %58
                OpReturn
                OpFunctionEnd
-          %f = OpFunction %void None %65
+%assign_and_preserve_padding_s = OpFunction %void None %59
+    %value_1 = OpFunctionParameter %_arr_S_uint_4
+         %62 = OpLabel
+          %i = OpVariable %_ptr_Function_uint Function %27
+%var_for_index = OpVariable %_ptr_Function__arr_S_uint_4 Function %77
+               OpStore %i %27
+               OpBranch %65
+         %65 = OpLabel
+               OpLoopMerge %66 %67 None
+               OpBranch %68
+         %68 = OpLabel
+         %70 = OpLoad %uint %i
+         %71 = OpULessThan %bool %70 %uint_4
+         %69 = OpLogicalNot %bool %71
+               OpSelectionMerge %73 None
+               OpBranchConditional %69 %74 %73
+         %74 = OpLabel
+               OpBranch %66
+         %73 = OpLabel
+               OpStore %var_for_index %value_1
+         %79 = OpLoad %uint %i
+         %80 = OpCompositeConstruct %_arr_uint_uint_1 %79
+         %81 = OpLoad %uint %i
+         %83 = OpAccessChain %_ptr_Function_S %var_for_index %81
+         %84 = OpLoad %S %83
+         %78 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %80 %84
+               OpBranch %67
          %67 = OpLabel
-         %70 = OpAccessChain %_ptr_Uniform__arr_S_uint_4 %u %uint_0
-         %71 = OpLoad %_arr_S_uint_4 %70
-         %68 = OpFunctionCall %void %assign_and_preserve_padding_s %71
-         %76 = OpAccessChain %_ptr_Uniform_S %u %uint_0 %int_2
-         %77 = OpLoad %S %76
-         %72 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %73 %77
-         %79 = OpAccessChain %_ptr_StorageBuffer_mat4v3float %s %uint_0 %int_3 %uint_1
-         %81 = OpAccessChain %_ptr_Uniform_mat4v3float %u %uint_0 %int_2 %uint_1
-         %82 = OpLoad %mat4v3float %81
-               OpStore %79 %82
-         %85 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %uint_1 %23
-         %87 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %23 %uint_1 %int_1
-         %88 = OpLoad %v3float %87
-         %89 = OpVectorShuffle %v3float %88 %88 2 0 1
-               OpStore %85 %89
+         %85 = OpLoad %uint %i
+         %86 = OpIAdd %uint %85 %uint_1
+               OpStore %i %86
+               OpBranch %65
+         %66 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %87
+         %89 = OpLabel
+         %92 = OpAccessChain %_ptr_Uniform__arr_S_uint_4 %u %uint_0
+         %93 = OpLoad %_arr_S_uint_4 %92
+         %90 = OpFunctionCall %void %assign_and_preserve_padding_s %93
+         %97 = OpAccessChain %_ptr_Uniform_S %u %uint_0 %int_2
+         %98 = OpLoad %S %97
+         %94 = OpFunctionCall %void %assign_and_preserve_padding_1_s_X %95 %98
+        %102 = OpAccessChain %_ptr_Uniform_mat4v3float %u %uint_0 %int_2 %uint_1
+        %103 = OpLoad %mat4v3float %102
+         %99 = OpFunctionCall %void %assign_and_preserve_padding_2_s_X_m %100 %103
+        %104 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1 %uint_1 %23
+        %106 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %23 %uint_1 %int_1
+        %107 = OpLoad %v3float %106
+        %108 = OpVectorShuffle %v3float %107 %107 2 0 1
+               OpStore %104 %108
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/unnested/mat2x3_f16/to_storage.wgsl.expected.glsl

@@ -10,12 +10,17 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   f16mat2x3 inner;
 } s;
 
+void assign_and_preserve_padding_s(f16mat2x3 value) {
+  s.inner[0] = value[0u];
+  s.inner[1] = value[1u];
+}
+
 f16mat2x3 load_u_inner() {
   return f16mat2x3(u.inner_0, u.inner_1);
 }
 
 void f() {
-  s.inner = load_u_inner();
+  assign_and_preserve_padding_s(load_u_inner());
   s.inner[1] = u.inner_0;
   s.inner[1] = u.inner_0.zxy;
   s.inner[0][1] = u.inner_1[0u];

test/tint/buffer/uniform/std140/unnested/mat2x3_f16/to_storage.wgsl.expected.msl

@@ -1,8 +1,13 @@
 #include <metal_stdlib>
 
 using namespace metal;
+void assign_and_preserve_padding(device half2x3* const dest, half2x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+}
+
 kernel void f(device half2x3* tint_symbol [[buffer(1)]], const constant half2x3* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   (*(tint_symbol))[1] = (*(tint_symbol_1))[0];
   (*(tint_symbol))[1] = half3((*(tint_symbol_1))[0]).zxy;
   (*(tint_symbol))[0][1] = (*(tint_symbol_1))[1][0];

test/tint/buffer/uniform/std140/unnested/mat2x3_f16/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 49
+; Bound: 56
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
@@ -18,6 +18,8 @@
                OpName %u_block "u_block"
                OpMemberName %u_block 0 "inner"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value "value"
                OpName %load_u_inner "load_u_inner"
                OpName %f "f"
                OpDecorate %u_block_std140 Block
@@ -41,47 +43,57 @@
     %u_block = OpTypeStruct %mat2v3half
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
-         %10 = OpTypeFunction %mat2v3half
+       %void = OpTypeVoid
+         %10 = OpTypeFunction %void %mat2v3half
        %uint = OpTypeInt 32 0
      %uint_0 = OpConstant %uint 0
-%_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
-     %uint_1 = OpConstant %uint 1
-       %void = OpTypeVoid
-         %25 = OpTypeFunction %void
-%_ptr_StorageBuffer_mat2v3half = OpTypePointer StorageBuffer %mat2v3half
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
+         %18 = OpConstantNull %int
 %_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
-         %42 = OpConstantNull %int
+         %21 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+     %uint_1 = OpConstant %uint 1
+         %27 = OpTypeFunction %mat2v3half
+%_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
+         %39 = OpTypeFunction %void
 %_ptr_StorageBuffer_half = OpTypePointer StorageBuffer %half
-         %45 = OpConstantNull %uint
 %_ptr_Uniform_half = OpTypePointer Uniform %half
-%load_u_inner = OpFunction %mat2v3half None %10
-         %12 = OpLabel
-         %18 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %19 = OpLoad %v3half %18
-         %22 = OpAccessChain %_ptr_Uniform_v3half %u %uint_1
-         %23 = OpLoad %v3half %22
-         %24 = OpCompositeConstruct %mat2v3half %19 %23
-               OpReturnValue %24
-               OpFunctionEnd
-          %f = OpFunction %void None %25
-         %28 = OpLabel
-         %30 = OpAccessChain %_ptr_StorageBuffer_mat2v3half %s %uint_0
-         %31 = OpFunctionCall %mat2v3half %load_u_inner
-               OpStore %30 %31
-         %35 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
-         %36 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %37 = OpLoad %v3half %36
-               OpStore %35 %37
-         %38 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
-         %39 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %40 = OpLoad %v3half %39
-         %41 = OpVectorShuffle %v3half %40 %40 2 0 1
-               OpStore %38 %41
-         %44 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %42 %int_1
-         %47 = OpAccessChain %_ptr_Uniform_half %u %uint_1 %45
-         %48 = OpLoad %half %47
-               OpStore %44 %48
+%assign_and_preserve_padding_s = OpFunction %void None %10
+      %value = OpFunctionParameter %mat2v3half
+         %14 = OpLabel
+         %20 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %18
+         %22 = OpCompositeExtract %v3half %value 0
+               OpStore %20 %22
+         %24 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %26 = OpCompositeExtract %v3half %value 1
+               OpStore %24 %26
+               OpReturn
+               OpFunctionEnd
+%load_u_inner = OpFunction %mat2v3half None %27
+         %29 = OpLabel
+         %33 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %34 = OpLoad %v3half %33
+         %36 = OpAccessChain %_ptr_Uniform_v3half %u %uint_1
+         %37 = OpLoad %v3half %36
+         %38 = OpCompositeConstruct %mat2v3half %34 %37
+               OpReturnValue %38
+               OpFunctionEnd
+          %f = OpFunction %void None %39
+         %41 = OpLabel
+         %43 = OpFunctionCall %mat2v3half %load_u_inner
+         %42 = OpFunctionCall %void %assign_and_preserve_padding_s %43
+         %44 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %45 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %46 = OpLoad %v3half %45
+               OpStore %44 %46
+         %47 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %48 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %49 = OpLoad %v3half %48
+         %50 = OpVectorShuffle %v3half %49 %49 2 0 1
+               OpStore %47 %50
+         %52 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %18 %int_1
+         %54 = OpAccessChain %_ptr_Uniform_half %u %uint_1 %21
+         %55 = OpLoad %half %54
+               OpStore %52 %55
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/unnested/mat2x3_f32/to_storage.wgsl.expected.glsl

@@ -8,8 +8,13 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   mat2x3 inner;
 } s;
 
+void assign_and_preserve_padding_s(mat2x3 value) {
+  s.inner[0] = value[0u];
+  s.inner[1] = value[1u];
+}
+
 void f() {
-  s.inner = u.inner;
+  assign_and_preserve_padding_s(u.inner);
   s.inner[1] = u.inner[0];
   s.inner[1] = u.inner[0].zxy;
   s.inner[0][1] = u.inner[1][0];

test/tint/buffer/uniform/std140/unnested/mat2x3_f32/to_storage.wgsl.expected.msl

@@ -1,8 +1,13 @@
 #include <metal_stdlib>
 
 using namespace metal;
+void assign_and_preserve_padding(device float2x3* const dest, float2x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+}
+
 kernel void f(device float2x3* tint_symbol [[buffer(1)]], const constant float2x3* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   (*(tint_symbol))[1] = (*(tint_symbol_1))[0];
   (*(tint_symbol))[1] = float3((*(tint_symbol_1))[0]).zxy;
   (*(tint_symbol))[0][1] = (*(tint_symbol_1))[1][0];

test/tint/buffer/uniform/std140/unnested/mat2x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 37
+; Bound: 46
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -11,6 +11,8 @@
                OpMemberName %u_block 0 "inner"
                OpName %u "u"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value "value"
                OpName %f "f"
                OpDecorate %u_block Block
                OpMemberDecorate %u_block 0 Offset 0
@@ -30,36 +32,48 @@
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
        %void = OpTypeVoid
-          %9 = OpTypeFunction %void
+          %9 = OpTypeFunction %void %mat2v3float
        %uint = OpTypeInt 32 0
      %uint_0 = OpConstant %uint 0
-%_ptr_StorageBuffer_mat2v3float = OpTypePointer StorageBuffer %mat2v3float
-%_ptr_Uniform_mat2v3float = OpTypePointer Uniform %mat2v3float
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
+         %17 = OpConstantNull %int
 %_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
-         %24 = OpConstantNull %int
+         %20 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+     %uint_1 = OpConstant %uint 1
+         %26 = OpTypeFunction %void
+%_ptr_Uniform_mat2v3float = OpTypePointer Uniform %mat2v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
 %_ptr_StorageBuffer_float = OpTypePointer StorageBuffer %float
 %_ptr_Uniform_float = OpTypePointer Uniform %float
-          %f = OpFunction %void None %9
-         %12 = OpLabel
-         %16 = OpAccessChain %_ptr_StorageBuffer_mat2v3float %s %uint_0
-         %18 = OpAccessChain %_ptr_Uniform_mat2v3float %u %uint_0
-         %19 = OpLoad %mat2v3float %18
-               OpStore %16 %19
+%assign_and_preserve_padding_s = OpFunction %void None %9
+      %value = OpFunctionParameter %mat2v3float
+         %13 = OpLabel
+         %19 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %17
+         %21 = OpCompositeExtract %v3float %value 0
+               OpStore %19 %21
          %23 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
-         %26 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %24
-         %27 = OpLoad %v3float %26
-               OpStore %23 %27
-         %28 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
-         %29 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %24
-         %30 = OpLoad %v3float %29
-         %31 = OpVectorShuffle %v3float %30 %30 2 0 1
-               OpStore %28 %31
-         %33 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %24 %int_1
-         %35 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %int_1 %24
-         %36 = OpLoad %float %35
-               OpStore %33 %36
+         %25 = OpCompositeExtract %v3float %value 1
+               OpStore %23 %25
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %26
+         %28 = OpLabel
+         %31 = OpAccessChain %_ptr_Uniform_mat2v3float %u %uint_0
+         %32 = OpLoad %mat2v3float %31
+         %29 = OpFunctionCall %void %assign_and_preserve_padding_s %32
+         %33 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
+         %35 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %17
+         %36 = OpLoad %v3float %35
+               OpStore %33 %36
+         %37 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
+         %38 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %17
+         %39 = OpLoad %v3float %38
+         %40 = OpVectorShuffle %v3float %39 %39 2 0 1
+               OpStore %37 %40
+         %42 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %17 %int_1
+         %44 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %int_1 %17
+         %45 = OpLoad %float %44
+               OpStore %42 %45
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/unnested/mat3x3_f16/to_storage.wgsl.expected.glsl

@@ -11,12 +11,18 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   f16mat3 inner;
 } s;
 
+void assign_and_preserve_padding_s(f16mat3 value) {
+  s.inner[0] = value[0u];
+  s.inner[1] = value[1u];
+  s.inner[2] = value[2u];
+}
+
 f16mat3 load_u_inner() {
   return f16mat3(u.inner_0, u.inner_1, u.inner_2);
 }
 
 void f() {
-  s.inner = load_u_inner();
+  assign_and_preserve_padding_s(load_u_inner());
   s.inner[1] = u.inner_0;
   s.inner[1] = u.inner_0.zxy;
   s.inner[0][1] = u.inner_1[0u];

test/tint/buffer/uniform/std140/unnested/mat3x3_f16/to_storage.wgsl.expected.msl

@@ -1,8 +1,14 @@
 #include <metal_stdlib>
 
 using namespace metal;
+void assign_and_preserve_padding(device half3x3* const dest, half3x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+}
+
 kernel void f(device half3x3* tint_symbol [[buffer(1)]], const constant half3x3* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   (*(tint_symbol))[1] = (*(tint_symbol_1))[0];
   (*(tint_symbol))[1] = half3((*(tint_symbol_1))[0]).zxy;
   (*(tint_symbol))[0][1] = (*(tint_symbol_1))[1][0];

test/tint/buffer/uniform/std140/unnested/mat3x3_f16/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 53
+; Bound: 63
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
@@ -19,6 +19,8 @@
                OpName %u_block "u_block"
                OpMemberName %u_block 0 "inner"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value "value"
                OpName %load_u_inner "load_u_inner"
                OpName %f "f"
                OpDecorate %u_block_std140 Block
@@ -43,50 +45,64 @@
     %u_block = OpTypeStruct %mat3v3half
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
-         %10 = OpTypeFunction %mat3v3half
+       %void = OpTypeVoid
+         %10 = OpTypeFunction %void %mat3v3half
        %uint = OpTypeInt 32 0
      %uint_0 = OpConstant %uint 0
-%_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
-     %uint_1 = OpConstant %uint 1
-     %uint_2 = OpConstant %uint 2
-       %void = OpTypeVoid
-         %29 = OpTypeFunction %void
-%_ptr_StorageBuffer_mat3v3half = OpTypePointer StorageBuffer %mat3v3half
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
+         %18 = OpConstantNull %int
 %_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
-         %46 = OpConstantNull %int
+         %21 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+     %uint_1 = OpConstant %uint 1
+      %int_2 = OpConstant %int 2
+     %uint_2 = OpConstant %uint 2
+         %31 = OpTypeFunction %mat3v3half
+%_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
+         %46 = OpTypeFunction %void
 %_ptr_StorageBuffer_half = OpTypePointer StorageBuffer %half
-         %49 = OpConstantNull %uint
 %_ptr_Uniform_half = OpTypePointer Uniform %half
-%load_u_inner = OpFunction %mat3v3half None %10
-         %12 = OpLabel
-         %18 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %19 = OpLoad %v3half %18
-         %22 = OpAccessChain %_ptr_Uniform_v3half %u %uint_1
-         %23 = OpLoad %v3half %22
-         %26 = OpAccessChain %_ptr_Uniform_v3half %u %uint_2
-         %27 = OpLoad %v3half %26
-         %28 = OpCompositeConstruct %mat3v3half %19 %23 %27
-               OpReturnValue %28
-               OpFunctionEnd
-          %f = OpFunction %void None %29
-         %32 = OpLabel
-         %34 = OpAccessChain %_ptr_StorageBuffer_mat3v3half %s %uint_0
-         %35 = OpFunctionCall %mat3v3half %load_u_inner
-               OpStore %34 %35
-         %39 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
-         %40 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %41 = OpLoad %v3half %40
-               OpStore %39 %41
-         %42 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
-         %43 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %44 = OpLoad %v3half %43
-         %45 = OpVectorShuffle %v3half %44 %44 2 0 1
-               OpStore %42 %45
-         %48 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %46 %int_1
-         %51 = OpAccessChain %_ptr_Uniform_half %u %uint_1 %49
-         %52 = OpLoad %half %51
-               OpStore %48 %52
+%assign_and_preserve_padding_s = OpFunction %void None %10
+      %value = OpFunctionParameter %mat3v3half
+         %14 = OpLabel
+         %20 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %18
+         %22 = OpCompositeExtract %v3half %value 0
+               OpStore %20 %22
+         %24 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %26 = OpCompositeExtract %v3half %value 1
+               OpStore %24 %26
+         %28 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_2
+         %30 = OpCompositeExtract %v3half %value 2
+               OpStore %28 %30
+               OpReturn
+               OpFunctionEnd
+%load_u_inner = OpFunction %mat3v3half None %31
+         %33 = OpLabel
+         %37 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %38 = OpLoad %v3half %37
+         %40 = OpAccessChain %_ptr_Uniform_v3half %u %uint_1
+         %41 = OpLoad %v3half %40
+         %43 = OpAccessChain %_ptr_Uniform_v3half %u %uint_2
+         %44 = OpLoad %v3half %43
+         %45 = OpCompositeConstruct %mat3v3half %38 %41 %44
+               OpReturnValue %45
+               OpFunctionEnd
+          %f = OpFunction %void None %46
+         %48 = OpLabel
+         %50 = OpFunctionCall %mat3v3half %load_u_inner
+         %49 = OpFunctionCall %void %assign_and_preserve_padding_s %50
+         %51 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %52 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %53 = OpLoad %v3half %52
+               OpStore %51 %53
+         %54 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %55 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %56 = OpLoad %v3half %55
+         %57 = OpVectorShuffle %v3half %56 %56 2 0 1
+               OpStore %54 %57
+         %59 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %18 %int_1
+         %61 = OpAccessChain %_ptr_Uniform_half %u %uint_1 %21
+         %62 = OpLoad %half %61
+               OpStore %59 %62
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/unnested/mat3x3_f32/to_storage.wgsl.expected.glsl

@@ -8,8 +8,14 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   mat3 inner;
 } s;
 
+void assign_and_preserve_padding_s(mat3 value) {
+  s.inner[0] = value[0u];
+  s.inner[1] = value[1u];
+  s.inner[2] = value[2u];
+}
+
 void f() {
-  s.inner = u.inner;
+  assign_and_preserve_padding_s(u.inner);
   s.inner[1] = u.inner[0];
   s.inner[1] = u.inner[0].zxy;
   s.inner[0][1] = u.inner[1][0];

test/tint/buffer/uniform/std140/unnested/mat3x3_f32/to_storage.wgsl.expected.msl

@@ -1,8 +1,14 @@
 #include <metal_stdlib>
 
 using namespace metal;
+void assign_and_preserve_padding(device float3x3* const dest, float3x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+}
+
 kernel void f(device float3x3* tint_symbol [[buffer(1)]], const constant float3x3* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   (*(tint_symbol))[1] = (*(tint_symbol_1))[0];
   (*(tint_symbol))[1] = float3((*(tint_symbol_1))[0]).zxy;
   (*(tint_symbol))[0][1] = (*(tint_symbol_1))[1][0];

test/tint/buffer/uniform/std140/unnested/mat3x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 37
+; Bound: 50
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -11,6 +11,8 @@
                OpMemberName %u_block 0 "inner"
                OpName %u "u"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value "value"
                OpName %f "f"
                OpDecorate %u_block Block
                OpMemberDecorate %u_block 0 Offset 0
@@ -30,36 +32,53 @@
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
        %void = OpTypeVoid
-          %9 = OpTypeFunction %void
+          %9 = OpTypeFunction %void %mat3v3float
        %uint = OpTypeInt 32 0
      %uint_0 = OpConstant %uint 0
-%_ptr_StorageBuffer_mat3v3float = OpTypePointer StorageBuffer %mat3v3float
-%_ptr_Uniform_mat3v3float = OpTypePointer Uniform %mat3v3float
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
+         %17 = OpConstantNull %int
 %_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
-         %24 = OpConstantNull %int
+         %20 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+     %uint_1 = OpConstant %uint 1
+      %int_2 = OpConstant %int 2
+     %uint_2 = OpConstant %uint 2
+         %30 = OpTypeFunction %void
+%_ptr_Uniform_mat3v3float = OpTypePointer Uniform %mat3v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
 %_ptr_StorageBuffer_float = OpTypePointer StorageBuffer %float
 %_ptr_Uniform_float = OpTypePointer Uniform %float
-          %f = OpFunction %void None %9
-         %12 = OpLabel
-         %16 = OpAccessChain %_ptr_StorageBuffer_mat3v3float %s %uint_0
-         %18 = OpAccessChain %_ptr_Uniform_mat3v3float %u %uint_0
-         %19 = OpLoad %mat3v3float %18
-               OpStore %16 %19
+%assign_and_preserve_padding_s = OpFunction %void None %9
+      %value = OpFunctionParameter %mat3v3float
+         %13 = OpLabel
+         %19 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %17
+         %21 = OpCompositeExtract %v3float %value 0
+               OpStore %19 %21
          %23 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
-         %26 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %24
-         %27 = OpLoad %v3float %26
-               OpStore %23 %27
-         %28 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
-         %29 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %24
-         %30 = OpLoad %v3float %29
-         %31 = OpVectorShuffle %v3float %30 %30 2 0 1
-               OpStore %28 %31
-         %33 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %24 %int_1
-         %35 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %int_1 %24
-         %36 = OpLoad %float %35
-               OpStore %33 %36
+         %25 = OpCompositeExtract %v3float %value 1
+               OpStore %23 %25
+         %27 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_2
+         %29 = OpCompositeExtract %v3float %value 2
+               OpStore %27 %29
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %30
+         %32 = OpLabel
+         %35 = OpAccessChain %_ptr_Uniform_mat3v3float %u %uint_0
+         %36 = OpLoad %mat3v3float %35
+         %33 = OpFunctionCall %void %assign_and_preserve_padding_s %36
+         %37 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
+         %39 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %17
+         %40 = OpLoad %v3float %39
+               OpStore %37 %40
+         %41 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
+         %42 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %17
+         %43 = OpLoad %v3float %42
+         %44 = OpVectorShuffle %v3float %43 %43 2 0 1
+               OpStore %41 %44
+         %46 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %17 %int_1
+         %48 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %int_1 %17
+         %49 = OpLoad %float %48
+               OpStore %46 %49
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/unnested/mat4x3_f16/to_storage.wgsl.expected.glsl

@@ -12,12 +12,19 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   f16mat4x3 inner;
 } s;
 
+void assign_and_preserve_padding_s(f16mat4x3 value) {
+  s.inner[0] = value[0u];
+  s.inner[1] = value[1u];
+  s.inner[2] = value[2u];
+  s.inner[3] = value[3u];
+}
+
 f16mat4x3 load_u_inner() {
   return f16mat4x3(u.inner_0, u.inner_1, u.inner_2, u.inner_3);
 }
 
 void f() {
-  s.inner = load_u_inner();
+  assign_and_preserve_padding_s(load_u_inner());
   s.inner[1] = u.inner_0;
   s.inner[1] = u.inner_0.zxy;
   s.inner[0][1] = u.inner_1[0u];

test/tint/buffer/uniform/std140/unnested/mat4x3_f16/to_storage.wgsl.expected.msl

@@ -1,8 +1,15 @@
 #include <metal_stdlib>
 
 using namespace metal;
+void assign_and_preserve_padding(device half4x3* const dest, half4x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+  (*(dest))[3u] = value[3u];
+}
+
 kernel void f(device half4x3* tint_symbol [[buffer(1)]], const constant half4x3* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   (*(tint_symbol))[1] = (*(tint_symbol_1))[0];
   (*(tint_symbol))[1] = half3((*(tint_symbol_1))[0]).zxy;
   (*(tint_symbol))[0][1] = (*(tint_symbol_1))[1][0];

test/tint/buffer/uniform/std140/unnested/mat4x3_f16/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 57
+; Bound: 70
 ; Schema: 0
                OpCapability Shader
                OpCapability Float16
@@ -20,6 +20,8 @@
                OpName %u_block "u_block"
                OpMemberName %u_block 0 "inner"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value "value"
                OpName %load_u_inner "load_u_inner"
                OpName %f "f"
                OpDecorate %u_block_std140 Block
@@ -45,53 +47,71 @@
     %u_block = OpTypeStruct %mat4v3half
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
-         %10 = OpTypeFunction %mat4v3half
+       %void = OpTypeVoid
+         %10 = OpTypeFunction %void %mat4v3half
        %uint = OpTypeInt 32 0
      %uint_0 = OpConstant %uint 0
-%_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
-     %uint_1 = OpConstant %uint 1
-     %uint_2 = OpConstant %uint 2
-     %uint_3 = OpConstant %uint 3
-       %void = OpTypeVoid
-         %33 = OpTypeFunction %void
-%_ptr_StorageBuffer_mat4v3half = OpTypePointer StorageBuffer %mat4v3half
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
+         %18 = OpConstantNull %int
 %_ptr_StorageBuffer_v3half = OpTypePointer StorageBuffer %v3half
-         %50 = OpConstantNull %int
+         %21 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+     %uint_1 = OpConstant %uint 1
+      %int_2 = OpConstant %int 2
+     %uint_2 = OpConstant %uint 2
+      %int_3 = OpConstant %int 3
+     %uint_3 = OpConstant %uint 3
+         %35 = OpTypeFunction %mat4v3half
+%_ptr_Uniform_v3half = OpTypePointer Uniform %v3half
+         %53 = OpTypeFunction %void
 %_ptr_StorageBuffer_half = OpTypePointer StorageBuffer %half
-         %53 = OpConstantNull %uint
 %_ptr_Uniform_half = OpTypePointer Uniform %half
-%load_u_inner = OpFunction %mat4v3half None %10
-         %12 = OpLabel
-         %18 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %19 = OpLoad %v3half %18
-         %22 = OpAccessChain %_ptr_Uniform_v3half %u %uint_1
-         %23 = OpLoad %v3half %22
-         %26 = OpAccessChain %_ptr_Uniform_v3half %u %uint_2
-         %27 = OpLoad %v3half %26
-         %30 = OpAccessChain %_ptr_Uniform_v3half %u %uint_3
-         %31 = OpLoad %v3half %30
-         %32 = OpCompositeConstruct %mat4v3half %19 %23 %27 %31
-               OpReturnValue %32
-               OpFunctionEnd
-          %f = OpFunction %void None %33
-         %36 = OpLabel
-         %38 = OpAccessChain %_ptr_StorageBuffer_mat4v3half %s %uint_0
-         %39 = OpFunctionCall %mat4v3half %load_u_inner
-               OpStore %38 %39
-         %43 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
-         %44 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %45 = OpLoad %v3half %44
-               OpStore %43 %45
-         %46 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
-         %47 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
-         %48 = OpLoad %v3half %47
-         %49 = OpVectorShuffle %v3half %48 %48 2 0 1
-               OpStore %46 %49
-         %52 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %50 %int_1
-         %55 = OpAccessChain %_ptr_Uniform_half %u %uint_1 %53
-         %56 = OpLoad %half %55
-               OpStore %52 %56
+%assign_and_preserve_padding_s = OpFunction %void None %10
+      %value = OpFunctionParameter %mat4v3half
+         %14 = OpLabel
+         %20 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %18
+         %22 = OpCompositeExtract %v3half %value 0
+               OpStore %20 %22
+         %24 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %26 = OpCompositeExtract %v3half %value 1
+               OpStore %24 %26
+         %28 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_2
+         %30 = OpCompositeExtract %v3half %value 2
+               OpStore %28 %30
+         %32 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_3
+         %34 = OpCompositeExtract %v3half %value 3
+               OpStore %32 %34
+               OpReturn
+               OpFunctionEnd
+%load_u_inner = OpFunction %mat4v3half None %35
+         %37 = OpLabel
+         %41 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %42 = OpLoad %v3half %41
+         %44 = OpAccessChain %_ptr_Uniform_v3half %u %uint_1
+         %45 = OpLoad %v3half %44
+         %47 = OpAccessChain %_ptr_Uniform_v3half %u %uint_2
+         %48 = OpLoad %v3half %47
+         %50 = OpAccessChain %_ptr_Uniform_v3half %u %uint_3
+         %51 = OpLoad %v3half %50
+         %52 = OpCompositeConstruct %mat4v3half %42 %45 %48 %51
+               OpReturnValue %52
+               OpFunctionEnd
+          %f = OpFunction %void None %53
+         %55 = OpLabel
+         %57 = OpFunctionCall %mat4v3half %load_u_inner
+         %56 = OpFunctionCall %void %assign_and_preserve_padding_s %57
+         %58 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %59 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %60 = OpLoad %v3half %59
+               OpStore %58 %60
+         %61 = OpAccessChain %_ptr_StorageBuffer_v3half %s %uint_0 %int_1
+         %62 = OpAccessChain %_ptr_Uniform_v3half %u %uint_0
+         %63 = OpLoad %v3half %62
+         %64 = OpVectorShuffle %v3half %63 %63 2 0 1
+               OpStore %61 %64
+         %66 = OpAccessChain %_ptr_StorageBuffer_half %s %uint_0 %18 %int_1
+         %68 = OpAccessChain %_ptr_Uniform_half %u %uint_1 %21
+         %69 = OpLoad %half %68
+               OpStore %66 %69
                OpReturn
                OpFunctionEnd

test/tint/buffer/uniform/std140/unnested/mat4x3_f32/to_storage.wgsl.expected.glsl

@@ -8,8 +8,15 @@ layout(binding = 1, std430) buffer u_block_ssbo {
   mat4x3 inner;
 } s;
 
+void assign_and_preserve_padding_s(mat4x3 value) {
+  s.inner[0] = value[0u];
+  s.inner[1] = value[1u];
+  s.inner[2] = value[2u];
+  s.inner[3] = value[3u];
+}
+
 void f() {
-  s.inner = u.inner;
+  assign_and_preserve_padding_s(u.inner);
   s.inner[1] = u.inner[0];
   s.inner[1] = u.inner[0].zxy;
   s.inner[0][1] = u.inner[1][0];

test/tint/buffer/uniform/std140/unnested/mat4x3_f32/to_storage.wgsl.expected.msl

@@ -1,8 +1,15 @@
 #include <metal_stdlib>
 
 using namespace metal;
+void assign_and_preserve_padding(device float4x3* const dest, float4x3 value) {
+  (*(dest))[0u] = value[0u];
+  (*(dest))[1u] = value[1u];
+  (*(dest))[2u] = value[2u];
+  (*(dest))[3u] = value[3u];
+}
+
 kernel void f(device float4x3* tint_symbol [[buffer(1)]], const constant float4x3* tint_symbol_1 [[buffer(0)]]) {
-  *(tint_symbol) = *(tint_symbol_1);
+  assign_and_preserve_padding(tint_symbol, *(tint_symbol_1));
   (*(tint_symbol))[1] = (*(tint_symbol_1))[0];
   (*(tint_symbol))[1] = float3((*(tint_symbol_1))[0]).zxy;
   (*(tint_symbol))[0][1] = (*(tint_symbol_1))[1][0];

test/tint/buffer/uniform/std140/unnested/mat4x3_f32/to_storage.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 37
+; Bound: 54
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
@@ -11,6 +11,8 @@
                OpMemberName %u_block 0 "inner"
                OpName %u "u"
                OpName %s "s"
+               OpName %assign_and_preserve_padding_s "assign_and_preserve_padding_s"
+               OpName %value "value"
                OpName %f "f"
                OpDecorate %u_block Block
                OpMemberDecorate %u_block 0 Offset 0
@@ -30,36 +32,58 @@
 %_ptr_StorageBuffer_u_block = OpTypePointer StorageBuffer %u_block
           %s = OpVariable %_ptr_StorageBuffer_u_block StorageBuffer
        %void = OpTypeVoid
-          %9 = OpTypeFunction %void
+          %9 = OpTypeFunction %void %mat4v3float
        %uint = OpTypeInt 32 0
      %uint_0 = OpConstant %uint 0
-%_ptr_StorageBuffer_mat4v3float = OpTypePointer StorageBuffer %mat4v3float
-%_ptr_Uniform_mat4v3float = OpTypePointer Uniform %mat4v3float
         %int = OpTypeInt 32 1
-      %int_1 = OpConstant %int 1
+         %17 = OpConstantNull %int
 %_ptr_StorageBuffer_v3float = OpTypePointer StorageBuffer %v3float
-         %24 = OpConstantNull %int
+         %20 = OpConstantNull %uint
+      %int_1 = OpConstant %int 1
+     %uint_1 = OpConstant %uint 1
+      %int_2 = OpConstant %int 2
+     %uint_2 = OpConstant %uint 2
+      %int_3 = OpConstant %int 3
+     %uint_3 = OpConstant %uint 3
+         %34 = OpTypeFunction %void
+%_ptr_Uniform_mat4v3float = OpTypePointer Uniform %mat4v3float
 %_ptr_Uniform_v3float = OpTypePointer Uniform %v3float
 %_ptr_StorageBuffer_float = OpTypePointer StorageBuffer %float
 %_ptr_Uniform_float = OpTypePointer Uniform %float
-          %f = OpFunction %void None %9
-         %12 = OpLabel
-         %16 = OpAccessChain %_ptr_StorageBuffer_mat4v3float %s %uint_0
-         %18 = OpAccessChain %_ptr_Uniform_mat4v3float %u %uint_0
-         %19 = OpLoad %mat4v3float %18
-               OpStore %16 %19
+%assign_and_preserve_padding_s = OpFunction %void None %9
+      %value = OpFunctionParameter %mat4v3float
+         %13 = OpLabel
+         %19 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %17
+         %21 = OpCompositeExtract %v3float %value 0
+               OpStore %19 %21
          %23 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
-         %26 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %24
-         %27 = OpLoad %v3float %26
-               OpStore %23 %27
-         %28 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
-         %29 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %24
-         %30 = OpLoad %v3float %29
-         %31 = OpVectorShuffle %v3float %30 %30 2 0 1
-               OpStore %28 %31
-         %33 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %24 %int_1
-         %35 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %int_1 %24
-         %36 = OpLoad %float %35
-               OpStore %33 %36
+         %25 = OpCompositeExtract %v3float %value 1
+               OpStore %23 %25
+         %27 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_2
+         %29 = OpCompositeExtract %v3float %value 2
+               OpStore %27 %29
+         %31 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_3
+         %33 = OpCompositeExtract %v3float %value 3
+               OpStore %31 %33
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %34
+         %36 = OpLabel
+         %39 = OpAccessChain %_ptr_Uniform_mat4v3float %u %uint_0
+         %40 = OpLoad %mat4v3float %39
+         %37 = OpFunctionCall %void %assign_and_preserve_padding_s %40
+         %41 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
+         %43 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %17
+         %44 = OpLoad %v3float %43
+               OpStore %41 %44
+         %45 = OpAccessChain %_ptr_StorageBuffer_v3float %s %uint_0 %int_1
+         %46 = OpAccessChain %_ptr_Uniform_v3float %u %uint_0 %17
+         %47 = OpLoad %v3float %46
+         %48 = OpVectorShuffle %v3float %47 %47 2 0 1
+               OpStore %45 %48
+         %50 = OpAccessChain %_ptr_StorageBuffer_float %s %uint_0 %17 %int_1
+         %52 = OpAccessChain %_ptr_Uniform_float %u %uint_0 %int_1 %17
+         %53 = OpLoad %float %52
+               OpStore %50 %53
                OpReturn
                OpFunctionEnd