writer/hlsl: Emit zero values for private variables

Also remove the unreachanble constructor logic in EmitHandleVariable.
Variables of the handle storage class cannot have initializers.

Fixed: tint:173
Change-Id: I7c997a8b6a70308ff9b5c42fa1198810ee365bac
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/55258
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/writer/hlsl/generator_impl.cc

@@ -2119,13 +2119,6 @@ bool GeneratorImpl::EmitHandleVariable(std::ostream& out,
   auto* decl = var->Declaration();
   auto* unwrapped_type = var->Type()->UnwrapRef();
 
-  std::ostringstream constructor_out;
-  if (auto* constructor = decl->constructor()) {
-    if (!EmitExpression(out, constructor_out, constructor)) {
-      return false;
-    }
-  }
-
   auto name = builder_.Symbols().NameFor(decl->symbol());
   auto* type = var->Type()->UnwrapRef();
   if (!EmitTypeAndName(out, type, var->StorageClass(), var->Access(), name)) {
@@ -2151,10 +2144,6 @@ bool GeneratorImpl::EmitHandleVariable(std::ostream& out,
         << bp.group->value() << ")";
   }
 
-  if (constructor_out.str().length()) {
-    out << " = " << constructor_out.str();
-  }
-
   out << ";" << std::endl;
   return true;
 }
@@ -2170,6 +2159,10 @@ bool GeneratorImpl::EmitPrivateVariable(std::ostream& out,
     if (!EmitExpression(out, constructor_out, constructor)) {
       return false;
     }
+  } else {
+    if (!EmitZeroValue(constructor_out, var->Type()->UnwrapRef())) {
+      return false;
+    }
   }
 
   out << "static ";

src/writer/hlsl/generator_impl_member_accessor_test.cc

@@ -136,7 +136,7 @@ TEST_F(HlslGeneratorImplTest_MemberAccessor, EmitExpression_MemberAccessor) {
   float mem;
 };
 
-static Data str;
+static Data str = {0.0f};
 
 [numthreads(1, 1, 1)]
 void test_function() {

src/writer/hlsl/generator_impl_variable_decl_statement_test.cc

@@ -75,7 +75,7 @@ TEST_F(HlslGeneratorImplTest_VariableDecl, Emit_VariableDeclStatement_Private) {
   gen.increment_indent();
 
   ASSERT_TRUE(gen.Generate(out)) << gen.error();
-  EXPECT_THAT(result(), HasSubstr("  static float a;\n"));
+  EXPECT_THAT(result(), HasSubstr("  static float a = 0.0f;\n"));
 }
 
 TEST_F(HlslGeneratorImplTest_VariableDecl,

test/array/assign_to_function_var.wgsl.expected.hlsl

@@ -27,7 +27,7 @@ tint_array_wrapper tint_symbol_4(RWByteAddressBuffer buffer, uint offset) {
   return tint_symbol_6;
 }
 
-static tint_array_wrapper src_private;
+static tint_array_wrapper src_private = {{{0}, {0}, {0}, {0}}};
 groupshared tint_array_wrapper src_workgroup;
 cbuffer cbuffer_src_uniform : register(b0, space0) {
   uint4 src_uniform[4];

test/array/assign_to_private_var.wgsl.expected.hlsl

@@ -27,13 +27,13 @@ tint_array_wrapper tint_symbol_4(RWByteAddressBuffer buffer, uint offset) {
   return tint_symbol_6;
 }
 
-static tint_array_wrapper src_private;
+static tint_array_wrapper src_private = {{{0}, {0}, {0}, {0}}};
 groupshared tint_array_wrapper src_workgroup;
 cbuffer cbuffer_src_uniform : register(b0, space0) {
   uint4 src_uniform[4];
 };
 RWByteAddressBuffer src_storage : register(u1, space0);
-static tint_array_wrapper tint_symbol;
+static tint_array_wrapper tint_symbol = {{{0}, {0}, {0}, {0}}};
 
 struct tint_array_wrapper_3 {
   int arr[2];
@@ -45,7 +45,7 @@ struct tint_array_wrapper_1 {
   tint_array_wrapper_2 arr[4];
 };
 
-static tint_array_wrapper_1 dst_nested;
+static tint_array_wrapper_1 dst_nested = {{{{{{0, 0}}, {{0, 0}}, {{0, 0}}}}, {{{{0, 0}}, {{0, 0}}, {{0, 0}}}}, {{{{0, 0}}, {{0, 0}}, {{0, 0}}}}, {{{{0, 0}}, {{0, 0}}, {{0, 0}}}}}};
 
 tint_array_wrapper ret_arr() {
   const tint_array_wrapper tint_symbol_7 = {{{0}, {0}, {0}, {0}}};

test/array/assign_to_storage_var.wgsl.expected.hlsl

@@ -62,7 +62,7 @@ void tint_symbol_10(RWByteAddressBuffer buffer, uint offset, tint_array_wrapper_
   tint_symbol_9(buffer, (offset + 72u), value.arr[3u]);
 }
 
-static tint_array_wrapper src_private;
+static tint_array_wrapper src_private = {{{0}, {0}, {0}, {0}}};
 groupshared tint_array_wrapper src_workgroup;
 cbuffer cbuffer_src_uniform : register(b0, space0) {
   uint4 src_uniform[4];

test/array/assign_to_workgroup_var.wgsl.expected.hlsl

@@ -27,7 +27,7 @@ tint_array_wrapper tint_symbol_4(RWByteAddressBuffer buffer, uint offset) {
   return tint_symbol_6;
 }
 
-static tint_array_wrapper src_private;
+static tint_array_wrapper src_private = {{{0}, {0}, {0}, {0}}};
 groupshared tint_array_wrapper src_workgroup;
 cbuffer cbuffer_src_uniform : register(b0, space0) {
   uint4 src_uniform[4];

test/bug/tint/749.spvasm.expected.hlsl

@@ -5,12 +5,12 @@ struct QuicksortObject {
   tint_array_wrapper numbers;
 };
 
-static QuicksortObject obj;
-static float4 gl_FragCoord;
+static QuicksortObject obj = {{{0, 0, 0, 0, 0, 0, 0, 0, 0, 0}}};
+static float4 gl_FragCoord = float4(0.0f, 0.0f, 0.0f, 0.0f);
 cbuffer cbuffer_x_188 : register(b0, space0) {
   uint4 x_188[1];
 };
-static float4 x_GLF_color;
+static float4 x_GLF_color = float4(0.0f, 0.0f, 0.0f, 0.0f);
 
 void swap_i1_i1_(inout int i, inout int j) {
   int temp = 0;

test/intrinsics/gen/frexp/53d417.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static uint3 arg_1;
+static uint3 arg_1 = uint3(0u, 0u, 0u);
 
 void frexp_53d417() {
   float3 tint_tmp;

test/intrinsics/gen/frexp/6efa09.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static int3 arg_1;
+static int3 arg_1 = int3(0, 0, 0);
 
 void frexp_6efa09() {
   float3 tint_tmp;

test/intrinsics/gen/frexp/a2a617.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static int arg_1;
+static int arg_1 = 0;
 
 void frexp_a2a617() {
   float tint_tmp;

test/intrinsics/gen/frexp/b45525.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static int4 arg_1;
+static int4 arg_1 = int4(0, 0, 0, 0);
 
 void frexp_b45525() {
   float4 tint_tmp;

test/intrinsics/gen/frexp/b7bcbb.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static uint arg_1;
+static uint arg_1 = 0u;
 
 void frexp_b7bcbb() {
   float tint_tmp;

test/intrinsics/gen/frexp/c084e3.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static int2 arg_1;
+static int2 arg_1 = int2(0, 0);
 
 void frexp_c084e3() {
   float2 tint_tmp;

test/intrinsics/gen/frexp/d14b16.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static uint4 arg_1;
+static uint4 arg_1 = uint4(0u, 0u, 0u, 0u);
 
 void frexp_d14b16() {
   float4 tint_tmp;

test/intrinsics/gen/frexp/e06acd.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static uint2 arg_1;
+static uint2 arg_1 = uint2(0u, 0u);
 
 void frexp_e06acd() {
   float2 tint_tmp;

test/intrinsics/gen/modf/3d00e2.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static float4 arg_1;
+static float4 arg_1 = float4(0.0f, 0.0f, 0.0f, 0.0f);
 
 void modf_3d00e2() {
   float4 res = modf(float4(0.0f, 0.0f, 0.0f, 0.0f), arg_1);

test/intrinsics/gen/modf/5e8476.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static float arg_1;
+static float arg_1 = 0.0f;
 
 void modf_5e8476() {
   float res = modf(1.0f, arg_1);

test/intrinsics/gen/modf/9c6a91.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static float2 arg_1;
+static float2 arg_1 = float2(0.0f, 0.0f);
 
 void modf_9c6a91() {
   float2 res = modf(float2(0.0f, 0.0f), arg_1);

test/intrinsics/gen/modf/9cecfc.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static float3 arg_1;
+static float3 arg_1 = float3(0.0f, 0.0f, 0.0f);
 
 void modf_9cecfc() {
   float3 res = modf(float3(0.0f, 0.0f, 0.0f), arg_1);

test/ptr_ref/load/global/i32.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static int I;
+static int I = 0;
 
 [numthreads(1, 1, 1)]
 void main() {

test/ptr_ref/load/global/struct_field.spvasm.expected.hlsl

@@ -2,7 +2,7 @@ struct S {
   int i;
 };
 
-static S V;
+static S V = {0};
 
 void main_1() {
   int i = 0;

test/ptr_ref/load/global/struct_field.wgsl.expected.hlsl

@@ -2,7 +2,7 @@ struct S {
   int i;
 };
 
-static S V;
+static S V = {0};
 
 [numthreads(1, 1, 1)]
 void main() {

test/ptr_ref/store/global/i32.wgsl.expected.hlsl

@@ -1,4 +1,4 @@
-static int I;
+static int I = 0;
 
 [numthreads(1, 1, 1)]
 void main() {

test/ptr_ref/store/global/struct_field.spvasm.expected.hlsl

@@ -2,7 +2,7 @@ struct S {
   int i;
 };
 
-static S V;
+static S V = {0};
 
 void main_1() {
   V.i = 5;

test/samples/simple_vertex.spvasm.expected.hlsl

@@ -1,4 +1,4 @@
-static float4 gl_Position;
+static float4 gl_Position = float4(0.0f, 0.0f, 0.0f, 0.0f);
 
 void main_1() {
   gl_Position = float4(0.0f, 0.0f, 0.0f, 0.0f);

test/types/module_scope_var.wgsl.expected.hlsl

@@ -1,21 +1,21 @@
 struct S {
 };
 
-static bool bool_var;
-static int i32_var;
-static uint u32_var;
-static float f32_var;
-static int2 v2i32_var;
-static uint3 v3u32_var;
-static float4 v4f32_var;
-static float2x3 m2x3_var;
+static bool bool_var = false;
+static int i32_var = 0;
+static uint u32_var = 0u;
+static float f32_var = 0.0f;
+static int2 v2i32_var = int2(0, 0);
+static uint3 v3u32_var = uint3(0u, 0u, 0u);
+static float4 v4f32_var = float4(0.0f, 0.0f, 0.0f, 0.0f);
+static float2x3 m2x3_var = float2x3(0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f);
 
 struct tint_array_wrapper {
   float arr[4];
 };
 
-static tint_array_wrapper arr_var;
-static S struct_var;
+static tint_array_wrapper arr_var = {{0.0f, 0.0f, 0.0f, 0.0f}};
+static S struct_var = {};
 
 [numthreads(1, 1, 1)]
 void main() {

test/var/private.wgsl.expected.hlsl

@@ -1,6 +1,6 @@
-static int a;
-static int b;
-static int c;
+static int a = 0;
+static int b = 0;
+static int c = 0;
 
 void uses_a() {
   a = (a + 1);