tint: Add basic support for chromium_experimental_push_constant.

This extension adds support for the push_constant storage class such
that it can be tested with WGSL test files. The real goal is to allow
future transforms that will add push constants that the SPIRV writer
will output.

The extension:

 - Adds the `chromium_experimental_push_constant` enable.
 - Allows the push_constant storage class for global variables.
 - Adds validation that the types are host-shareable for push_constant
   variables, and that they don't contain f16 (must be 32bit types
   only).
 - Validates that at most one push_constant variable is statically used
   per entry-point.
 - Skips validation that the extension has been enabled if
   kIgnoreStorageClass is used.

Tests are added:

 - For parsing of var<push_constant>
   - Caught a missing conversion.
 - For each of the validation rules.
 - For the wrapping of push constants in structs if needed by
   AddSpirvBlockAttribute.
 - For the layout and type rules of the storage class.
 - For a shader with multiple entry-points using various push constants.
    - Caught a missing reset of the previous push constant variable in
      the validation check that at most one is used.
    - Caught the missing wrapping in structs that had to be added to
      AddSpirvBlockAttribute.
    - Caught incorrect logic when adding diagnostics about the call
      graph leading to the reference to push constants.

Bug: tint:1620
Change-Id: I04a5d8e5188c0dcef077f2233ba1359d1575bf51
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/96682
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Ben Clayton <bclayton@google.com>

test/tint/var/uses/push_constant.wgsl

@@ -0,0 +1,36 @@
+enable chromium_experimental_push_constant;
+
+var<push_constant> a : i32;
+var<push_constant> b : i32;
+var<push_constant> c : i32; // unused
+
+fn uses_a() {
+  let foo = a;
+}
+
+fn uses_uses_a() {
+  uses_a();
+}
+
+fn uses_b() {
+  let foo = b;
+}
+
+@compute @workgroup_size(1)
+fn main1() {
+  uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main2() {
+  uses_uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main3() {
+  uses_b();
+}
+
+@compute @workgroup_size(1)
+fn main4() {
+}

test/tint/var/uses/push_constant.wgsl.expected.dxc.hlsl

@@ -0,0 +1,43 @@
+SKIP: FAILED
+
+
+enable chromium_experimental_push_constant;
+
+var<push_constant> a : i32;
+
+var<push_constant> b : i32;
+
+var<push_constant> c : i32;
+
+fn uses_a() {
+  let foo = a;
+}
+
+fn uses_uses_a() {
+  uses_a();
+}
+
+fn uses_b() {
+  let foo = b;
+}
+
+@compute @workgroup_size(1)
+fn main1() {
+  uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main2() {
+  uses_uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main3() {
+  uses_b();
+}
+
+@compute @workgroup_size(1)
+fn main4() {
+}
+
+Failed to generate: error: unhandled storage class push_constant

test/tint/var/uses/push_constant.wgsl.expected.fxc.hlsl

@@ -0,0 +1,43 @@
+SKIP: FAILED
+
+
+enable chromium_experimental_push_constant;
+
+var<push_constant> a : i32;
+
+var<push_constant> b : i32;
+
+var<push_constant> c : i32;
+
+fn uses_a() {
+  let foo = a;
+}
+
+fn uses_uses_a() {
+  uses_a();
+}
+
+fn uses_b() {
+  let foo = b;
+}
+
+@compute @workgroup_size(1)
+fn main1() {
+  uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main2() {
+  uses_uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main3() {
+  uses_b();
+}
+
+@compute @workgroup_size(1)
+fn main4() {
+}
+
+Failed to generate: error: unhandled storage class push_constant

test/tint/var/uses/push_constant.wgsl.expected.glsl

@@ -0,0 +1,135 @@
+SKIP: FAILED
+
+
+enable chromium_experimental_push_constant;
+
+var<push_constant> a : i32;
+
+var<push_constant> b : i32;
+
+var<push_constant> c : i32;
+
+fn uses_a() {
+  let foo = a;
+}
+
+fn uses_uses_a() {
+  uses_a();
+}
+
+fn uses_b() {
+  let foo = b;
+}
+
+@compute @workgroup_size(1)
+fn main1() {
+  uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main2() {
+  uses_uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main3() {
+  uses_b();
+}
+
+@compute @workgroup_size(1)
+fn main4() {
+}
+
+Failed to generate: error: unhandled storage class push_constant
+
+enable chromium_experimental_push_constant;
+
+var<push_constant> a : i32;
+
+var<push_constant> b : i32;
+
+var<push_constant> c : i32;
+
+fn uses_a() {
+  let foo = a;
+}
+
+fn uses_uses_a() {
+  uses_a();
+}
+
+fn uses_b() {
+  let foo = b;
+}
+
+@compute @workgroup_size(1)
+fn main1() {
+  uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main2() {
+  uses_uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main3() {
+  uses_b();
+}
+
+@compute @workgroup_size(1)
+fn main4() {
+}
+
+Failed to generate: error: unhandled storage class push_constant
+
+enable chromium_experimental_push_constant;
+
+var<push_constant> a : i32;
+
+var<push_constant> b : i32;
+
+var<push_constant> c : i32;
+
+fn uses_a() {
+  let foo = a;
+}
+
+fn uses_uses_a() {
+  uses_a();
+}
+
+fn uses_b() {
+  let foo = b;
+}
+
+@compute @workgroup_size(1)
+fn main1() {
+  uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main2() {
+  uses_uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main3() {
+  uses_b();
+}
+
+@compute @workgroup_size(1)
+fn main4() {
+}
+
+Failed to generate: error: unhandled storage class push_constant
+#version 310 es
+
+void main4() {
+}
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void main() {
+  main4();
+  return;
+}

test/tint/var/uses/push_constant.wgsl.expected.msl

@@ -0,0 +1,48 @@
+SKIP: FAILED
+
+
+enable chromium_experimental_push_constant;
+
+var<push_constant> a : i32;
+
+var<push_constant> b : i32;
+
+var<push_constant> c : i32;
+
+fn uses_a() {
+  let foo = a;
+}
+
+fn uses_uses_a() {
+  uses_a();
+}
+
+fn uses_b() {
+  let foo = b;
+}
+
+@compute @workgroup_size(1)
+fn main1() {
+  uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main2() {
+  uses_uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main3() {
+  uses_b();
+}
+
+@compute @workgroup_size(1)
+fn main4() {
+}
+
+Failed to generate: error: unhandled module-scope storage class (push_constant)
+error: unhandled module-scope storage class (push_constant)
+error: unhandled module-scope storage class (push_constant)
+error: unhandled module-scope storage class (push_constant)
+error: unhandled module-scope storage class (push_constant)
+error: unhandled module-scope storage class (push_constant)

test/tint/var/uses/push_constant.wgsl.expected.spvasm

@@ -0,0 +1,76 @@
+; SPIR-V
+; Version: 1.3
+; Generator: Google Tint Compiler; 0
+; Bound: 34
+; Schema: 0
+               OpCapability Shader
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %main1 "main1"
+               OpEntryPoint GLCompute %main2 "main2"
+               OpEntryPoint GLCompute %main3 "main3"
+               OpEntryPoint GLCompute %main4 "main4"
+               OpExecutionMode %main1 LocalSize 1 1 1
+               OpExecutionMode %main2 LocalSize 1 1 1
+               OpExecutionMode %main3 LocalSize 1 1 1
+               OpExecutionMode %main4 LocalSize 1 1 1
+               OpName %a_block "a_block"
+               OpMemberName %a_block 0 "inner"
+               OpName %a "a"
+               OpName %b "b"
+               OpName %c "c"
+               OpName %uses_a "uses_a"
+               OpName %uses_uses_a "uses_uses_a"
+               OpName %uses_b "uses_b"
+               OpName %main1 "main1"
+               OpName %main2 "main2"
+               OpName %main3 "main3"
+               OpName %main4 "main4"
+               OpDecorate %a_block Block
+               OpMemberDecorate %a_block 0 Offset 0
+        %int = OpTypeInt 32 1
+    %a_block = OpTypeStruct %int
+%_ptr_PushConstant_a_block = OpTypePointer PushConstant %a_block
+          %a = OpVariable %_ptr_PushConstant_a_block PushConstant
+          %b = OpVariable %_ptr_PushConstant_a_block PushConstant
+          %c = OpVariable %_ptr_PushConstant_a_block PushConstant
+       %void = OpTypeVoid
+          %7 = OpTypeFunction %void
+       %uint = OpTypeInt 32 0
+     %uint_0 = OpConstant %uint 0
+%_ptr_PushConstant_int = OpTypePointer PushConstant %int
+     %uses_a = OpFunction %void None %7
+         %10 = OpLabel
+         %14 = OpAccessChain %_ptr_PushConstant_int %a %uint_0
+         %15 = OpLoad %int %14
+               OpReturn
+               OpFunctionEnd
+%uses_uses_a = OpFunction %void None %7
+         %17 = OpLabel
+         %18 = OpFunctionCall %void %uses_a
+               OpReturn
+               OpFunctionEnd
+     %uses_b = OpFunction %void None %7
+         %20 = OpLabel
+         %21 = OpAccessChain %_ptr_PushConstant_int %b %uint_0
+         %22 = OpLoad %int %21
+               OpReturn
+               OpFunctionEnd
+      %main1 = OpFunction %void None %7
+         %24 = OpLabel
+         %25 = OpFunctionCall %void %uses_a
+               OpReturn
+               OpFunctionEnd
+      %main2 = OpFunction %void None %7
+         %27 = OpLabel
+         %28 = OpFunctionCall %void %uses_uses_a
+               OpReturn
+               OpFunctionEnd
+      %main3 = OpFunction %void None %7
+         %30 = OpLabel
+         %31 = OpFunctionCall %void %uses_b
+               OpReturn
+               OpFunctionEnd
+      %main4 = OpFunction %void None %7
+         %33 = OpLabel
+               OpReturn
+               OpFunctionEnd

test/tint/var/uses/push_constant.wgsl.expected.wgsl

@@ -0,0 +1,38 @@
+enable chromium_experimental_push_constant;
+
+var<push_constant> a : i32;
+
+var<push_constant> b : i32;
+
+var<push_constant> c : i32;
+
+fn uses_a() {
+  let foo = a;
+}
+
+fn uses_uses_a() {
+  uses_a();
+}
+
+fn uses_b() {
+  let foo = b;
+}
+
+@compute @workgroup_size(1)
+fn main1() {
+  uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main2() {
+  uses_uses_a();
+}
+
+@compute @workgroup_size(1)
+fn main3() {
+  uses_b();
+}
+
+@compute @workgroup_size(1)
+fn main4() {
+}