spirv-reader: builtin in/out keep their signedness as private vars

Update the plan for pipeline I/O.

Bug: tint:508
Change-Id: I263d954403134a78106b3372ec9df3d9d868ef1d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54462
Auto-Submit: David Neto <dneto@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: David Neto <dneto@google.com>
Reviewed-by: James Price <jrprice@google.com>

docs/spirv-input-output-variables.md

@@ -36,19 +36,22 @@ inputs and outputs, and two functions:
   is the same as the original SPIR-V entry point.
 - Original input variables are mapped to pseudo-in Private variables
   with the same store types, but no other attributes or properties copied.
+  In Vulkan, Input variables don't have initalizers.
 - Original output variables are mapped to pseudo-out Private variables
-  with the same store types, but no other attributes or properties are copied.
+  with the same store types and optional initializer, but no other attributes
+  or properties are copied.
 - A wrapper entry point function whose arguments correspond in type, location
   and builtin attributes the original input variables, and whose return type is
   a structure containing members correspond in type, location, and builtin
   attributes to the original output variables.
   The body of the wrapper function the following phases:
   - Copy formal parameter values into pseudo-in variables.
-  - Use stores to initialize pseudo-out variables:
+    - Insert a bitcast if the WGSL builtin variable has different signedness
-    - If the original variable had an initializer, store that value.
+      from the SPIR-V declared type.
-    - Otherwise, store a zero value for the store type.
   - Execute the inner function.
   - Copy pseudo-out variables into the return structure.
+    - Insert a bitcast if the WGSL builtin variable has different signedness
+      from the SPIR-V declared type.
   - Return the return structure.
 
 - Replace uses of the the original input/output variables to the pseudo-in and

src/reader/spirv/function.cc

@@ -957,6 +957,8 @@ bool FunctionEmitter::EmitEntryPointAsWrapper() {
       continue;
     }
 
+    // In Vulkan SPIR-V, Input variables must not have an initializer.
+
     const auto var_name = namer_.GetName(var_id);
     const auto var_sym = builder_.Symbols().Register(var_name);
     const auto param_name = namer_.MakeDerivedName(var_name + "_param");

src/reader/spirv/parser_impl_module_var_test.cc

@@ -80,6 +80,7 @@ std::string CommonTypes() {
     %float_1p5 = OpConstant %float 1.5
     %uint_1 = OpConstant %uint 1
     %int_m1 = OpConstant %int -1
+    %int_14 = OpConstant %int 14
     %uint_2 = OpConstant %uint 2
 
     %v2bool = OpTypeVector %bool 2
@@ -4018,6 +4019,157 @@ TEST_F(SpvModuleScopeVarParserTest, OutputVarsConvertedToPrivate) {
   EXPECT_THAT(got, HasSubstr(expected)) << got;
 }
 
+TEST_F(SpvModuleScopeVarParserTest,
+       OutputVarsConvertedToPrivate_WithInitializer) {
+  const auto assembly = Preamble() + FragMain() + CommonTypes() + R"(
+     %ptr_out_uint = OpTypePointer Output %uint
+     %1 = OpVariable %ptr_out_uint Output %uint_1
+  )" + MainBody();
+  auto p = parser(test::Assemble(assembly));
+
+  // TODO(crbug.com/tint/508): Remove this when everything is converted
+  // to HLSL style pipeline IO.
+  p->SetHLSLStylePipelineIO();
+
+  ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions());
+  EXPECT_TRUE(p->error().empty());
+  const auto got = p->program().to_str();
+  const std::string expected =
+      R"(Variable{
+    x_1
+    private
+    undefined
+    __u32
+    {
+      ScalarConstructor[not set]{1u}
+    }
+  }
+)";
+  EXPECT_THAT(got, HasSubstr(expected)) << got;
+}
+
+TEST_F(SpvModuleScopeVarParserTest,
+       Builtin_Output_Initializer_SameSignednessAsWGSL) {
+  // Only outputs can have initializers.
+  // WGSL sample_mask store type is u32.
+  const auto assembly = Preamble() + FragMain() + R"(
+     OpDecorate %1 BuiltIn SampleMask
+)" + CommonTypes() + R"(
+     %ptr_ty = OpTypePointer Output %uint
+     %1 = OpVariable %ptr_ty Output %uint_1
+  )" + MainBody();
+  auto p = parser(test::Assemble(assembly));
+
+  // TODO(crbug.com/tint/508): Remove this when everything is converted
+  // to HLSL style pipeline IO.
+  p->SetHLSLStylePipelineIO();
+
+  ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions());
+  EXPECT_TRUE(p->error().empty());
+  const auto got = p->program().to_str();
+  const std::string expected =
+      R"(Variable{
+    x_1
+    private
+    undefined
+    __u32
+    {
+      ScalarConstructor[not set]{1u}
+    }
+  }
+)";
+  EXPECT_THAT(got, HasSubstr(expected)) << got;
+}
+
+TEST_F(SpvModuleScopeVarParserTest,
+       Builtin_Output_Initializer_OppositeSignednessAsWGSL) {
+  // Only outputs can have initializers.
+  // WGSL sample_mask store type is u32.  Use i32 in SPIR-V
+  const auto assembly = Preamble() + FragMain() + R"(
+     OpDecorate %1 BuiltIn SampleMask
+)" + CommonTypes() + R"(
+     %ptr_ty = OpTypePointer Output %int
+     %1 = OpVariable %ptr_ty Output %int_14
+  )" + MainBody();
+  auto p = parser(test::Assemble(assembly));
+
+  // TODO(crbug.com/tint/508): Remove this when everything is converted
+  // to HLSL style pipeline IO.
+  p->SetHLSLStylePipelineIO();
+
+  ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions());
+  EXPECT_TRUE(p->error().empty());
+  const auto got = p->program().to_str();
+  const std::string expected =
+      R"(Variable{
+    x_1
+    private
+    undefined
+    __i32
+    {
+      ScalarConstructor[not set]{14}
+    }
+  }
+)";
+  EXPECT_THAT(got, HasSubstr(expected)) << got;
+}
+
+TEST_F(SpvModuleScopeVarParserTest, Builtin_Input_SameSignednessAsWGSL) {
+  // WGSL vertex_index store type is u32.
+  const auto assembly = Preamble() + FragMain() + R"(
+     OpDecorate %1 BuiltIn VertexIndex
+)" + CommonTypes() + R"(
+     %ptr_ty = OpTypePointer Input %uint
+     %1 = OpVariable %ptr_ty Input
+  )" + MainBody();
+  auto p = parser(test::Assemble(assembly));
+
+  // TODO(crbug.com/tint/508): Remove this when everything is converted
+  // to HLSL style pipeline IO.
+  p->SetHLSLStylePipelineIO();
+
+  ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions());
+  EXPECT_TRUE(p->error().empty());
+  const auto got = p->program().to_str();
+  const std::string expected =
+      R"(Variable{
+    x_1
+    private
+    undefined
+    __u32
+  }
+)";
+  EXPECT_THAT(got, HasSubstr(expected)) << got;
+}
+
+TEST_F(SpvModuleScopeVarParserTest, Builtin_Input_OppositeSignednessAsWGSL) {
+  // WGSL vertex_index store type is u32.  Use i32 in SPIR-V.
+  const auto assembly = Preamble() + FragMain() + R"(
+     OpDecorate %1 BuiltIn VertexIndex
+)" + CommonTypes() + R"(
+     %ptr_ty = OpTypePointer Input %int
+     %1 = OpVariable %ptr_ty Input
+  )" + MainBody();
+  auto p = parser(test::Assemble(assembly));
+
+  // TODO(crbug.com/tint/508): Remove this when everything is converted
+  // to HLSL style pipeline IO.
+  p->SetHLSLStylePipelineIO();
+
+  ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions());
+  EXPECT_TRUE(p->error().empty());
+  const auto got = p->program().to_str();
+  const std::string expected =
+      R"(Variable{
+    x_1
+    private
+    undefined
+    __i32
+  }
+)";
+  EXPECT_THAT(got, HasSubstr(expected)) << got;
+}
+
 TEST_F(SpvModuleScopeVarParserTest, EntryPointWrapping_IOLocations) {
   const auto assembly = CommonCapabilities() + R"(
      OpEntryPoint Vertex %main "main" %1 %2 %3 %4
@@ -4136,6 +4288,12 @@ TEST_F(SpvModuleScopeVarParserTest, EntryPointWrapping_IOLocations) {
   EXPECT_THAT(got, HasSubstr(expected)) << got;
 }
 
+// TODO(dneto): pipeline IO: convert signedness on builtin inputs in the wrapper
+// body
+// TODO(dneto): pipeline IO: convert signedness on builtin outputs in the
+// wrapper body
+// TODO(dneto): pipeline IO: flatten structures, and distribute locations
+
 // TODO(dneto): Test passing pointer to SampleMask as function parameter,
 // both input case and output case.