[hlsl-writer] Add alias type support.

This CL adds support for emitting type aliases to the HLSL backend.

Bug: tint:7
Change-Id: Ibd2c2d3bbe6c9a86033e379b4e1cb494259b4df2
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/25800
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>

BUILD.gn

@@ -1041,6 +1041,7 @@ source_set("tint_unittests_msl_writer_src") {
 
 source_set("tint_unittests_hlsl_writer_src") {
   sources = [
+    "src/writer/hlsl/generator_impl_alias_type_test.cc",
     "src/writer/hlsl/generator_impl_assign_test.cc",
     "src/writer/hlsl/generator_impl_binary_test.cc",
     "src/writer/hlsl/generator_impl_break_test.cc",

src/CMakeLists.txt

@@ -549,6 +549,7 @@ endif()
 
 if (${TINT_BUILD_HLSL_WRITER})
   list(APPEND TINT_TEST_SRCS
+    writer/hlsl/generator_impl_alias_type_test.cc
     writer/hlsl/generator_impl_assign_test.cc
     writer/hlsl/generator_impl_binary_test.cc
     writer/hlsl/generator_impl_break_test.cc

src/writer/hlsl/generator_impl.cc

@@ -57,6 +57,16 @@ bool GeneratorImpl::Generate() {
   for (const auto& global : module_->global_variables()) {
     global_variables_.set(global->name(), global.get());
   }
+
+  for (auto* const alias : module_->alias_types()) {
+    if (!EmitAliasType(alias)) {
+      return false;
+    }
+  }
+  if (!module_->alias_types().empty()) {
+    out_ << std::endl;
+  }
+
   return true;
 }
 
@@ -81,6 +91,17 @@ std::string GeneratorImpl::current_ep_var_name(VarType type) {
   return name;
 }
 
+bool GeneratorImpl::EmitAliasType(const ast::type::AliasType* alias) {
+  make_indent();
+  out_ << "typedef ";
+  if (!EmitType(alias->type(), "")) {
+    return false;
+  }
+  out_ << " " << namer_.NameFor(alias->name()) << ";" << std::endl;
+
+  return true;
+}
+
 bool GeneratorImpl::EmitAssign(ast::AssignmentStatement* stmt) {
   make_indent();
 

src/writer/hlsl/generator_impl.h

@@ -38,6 +38,10 @@ class GeneratorImpl : public TextGenerator {
   /// @returns true on successful generation; false otherwise
   bool Generate();
 
+  /// Handles generating an alias
+  /// @param alias the alias to generate
+  /// @returns true if the alias was emitted
+  bool EmitAliasType(const ast::type::AliasType* alias);
   /// Handles an assignment statement
   /// @param stmt the statement to emit
   /// @returns true if the statement was emitted successfully

src/writer/hlsl/generator_impl_alias_type_test.cc

@@ -0,0 +1,87 @@
+// Copyright 2020 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "gtest/gtest.h"
+#include "src/ast/module.h"
+#include "src/ast/struct.h"
+#include "src/ast/struct_member.h"
+#include "src/ast/struct_member_decoration.h"
+#include "src/ast/struct_member_offset_decoration.h"
+#include "src/ast/type/f32_type.h"
+#include "src/ast/type/i32_type.h"
+#include "src/ast/type/struct_type.h"
+#include "src/writer/hlsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace hlsl {
+namespace {
+
+using HlslGeneratorImplTest = testing::Test;
+
+TEST_F(HlslGeneratorImplTest, EmitAliasType_F32) {
+  ast::type::F32Type f32;
+  ast::type::AliasType alias("a", &f32);
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  ASSERT_TRUE(g.EmitAliasType(&alias)) << g.error();
+  EXPECT_EQ(g.result(), R"(typedef float a;
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, EmitAliasType_NameCollision) {
+  ast::type::F32Type f32;
+  ast::type::AliasType alias("float", &f32);
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  ASSERT_TRUE(g.EmitAliasType(&alias)) << g.error();
+  EXPECT_EQ(g.result(), R"(typedef float float_tint_0;
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, EmitAliasType_Struct) {
+  ast::type::I32Type i32;
+  ast::type::F32Type f32;
+
+  ast::StructMemberList members;
+  members.push_back(std::make_unique<ast::StructMember>(
+      "a", &f32, ast::StructMemberDecorationList{}));
+
+  ast::StructMemberDecorationList b_deco;
+  b_deco.push_back(std::make_unique<ast::StructMemberOffsetDecoration>(4));
+  members.push_back(
+      std::make_unique<ast::StructMember>("b", &i32, std::move(b_deco)));
+
+  auto str = std::make_unique<ast::Struct>();
+  str->set_members(std::move(members));
+
+  ast::type::StructType s(std::move(str));
+  ast::type::AliasType alias("a", &s);
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  ASSERT_TRUE(g.EmitAliasType(&alias)) << g.error();
+  EXPECT_EQ(g.result(), R"(typedef struct {
+  float a;
+  int b;
+} a;
+)");
+}
+
+}  // namespace
+}  // namespace hlsl
+}  // namespace writer
+}  // namespace tint