[hlsl-writer] Add member accessor emission.

This CL adds emitting MemberAccessorExpressions to the HLSL backend.

Bug: tint:7
Change-Id: Ic6c99232e98322c8145700d5f1a3a8314cf60feb
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/25844
Reviewed-by: David Neto <dneto@google.com>

BUILD.gn

@@ -1053,6 +1053,7 @@ source_set("tint_unittests_hlsl_writer_src") {
     "src/writer/hlsl/generator_impl_continue_test.cc",
     "src/writer/hlsl/generator_impl_discard_test.cc",
     "src/writer/hlsl/generator_impl_identifier_test.cc",
+    "src/writer/hlsl/generator_impl_member_accessor_test.cc",
     "src/writer/hlsl/generator_impl_return_test.cc",
     "src/writer/hlsl/generator_impl_switch_test.cc",
     "src/writer/hlsl/generator_impl_test.cc",

src/CMakeLists.txt

@@ -561,6 +561,7 @@ if (${TINT_BUILD_HLSL_WRITER})
     writer/hlsl/generator_impl_continue_test.cc
     writer/hlsl/generator_impl_discard_test.cc
     writer/hlsl/generator_impl_identifier_test.cc
+    writer/hlsl/generator_impl_member_accessor_test.cc
     writer/hlsl/generator_impl_return_test.cc
     writer/hlsl/generator_impl_switch_test.cc
     writer/hlsl/generator_impl_test.cc

src/writer/hlsl/generator_impl.cc

@@ -22,6 +22,7 @@
 #include "src/ast/case_statement.h"
 #include "src/ast/float_literal.h"
 #include "src/ast/identifier_expression.h"
+#include "src/ast/member_accessor_expression.h"
 #include "src/ast/return_statement.h"
 #include "src/ast/sint_literal.h"
 #include "src/ast/struct.h"
@@ -403,6 +404,9 @@ bool GeneratorImpl::EmitExpression(ast::Expression* expr) {
   if (expr->IsIdentifier()) {
     return EmitIdentifier(expr->AsIdentifier());
   }
+  if (expr->IsMemberAccessor()) {
+    return EmitMemberAccessor(expr->AsMemberAccessor());
+  }
   if (expr->IsUnaryOp()) {
     return EmitUnaryOp(expr->AsUnaryOp());
   }
@@ -485,6 +489,14 @@ bool GeneratorImpl::EmitZeroValue(ast::type::Type* type) {
   return true;
 }
 
+bool GeneratorImpl::EmitMemberAccessor(ast::MemberAccessorExpression* expr) {
+  if (!EmitExpression(expr->structure())) {
+    return false;
+  }
+  out_ << ".";
+  return EmitExpression(expr->member());
+}
+
 bool GeneratorImpl::EmitReturn(ast::ReturnStatement* stmt) {
   make_indent();
 

src/writer/hlsl/generator_impl.h

@@ -110,6 +110,10 @@ class GeneratorImpl : public TextGenerator {
   /// @param expr the identifier expression
   /// @returns true if the identifeir was emitted
   bool EmitIdentifier(ast::IdentifierExpression* expr);
+  /// Handles a member accessor expression
+  /// @param expr the member accessor expression
+  /// @returns true if the member accessor was emitted
+  bool EmitMemberAccessor(ast::MemberAccessorExpression* expr);
   /// Handles return statements
   /// @param stmt the statement to emit
   /// @returns true if the statement was successfully emitted

src/writer/hlsl/generator_impl_member_accessor_test.cc

@@ -0,0 +1,45 @@
+// 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 <memory>
+
+#include "gtest/gtest.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/member_accessor_expression.h"
+#include "src/ast/module.h"
+#include "src/writer/hlsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace hlsl {
+namespace {
+
+using HlslGeneratorImplTest = testing::Test;
+
+TEST_F(HlslGeneratorImplTest, EmitExpression_MemberAccessor) {
+  auto str = std::make_unique<ast::IdentifierExpression>("str");
+  auto mem = std::make_unique<ast::IdentifierExpression>("mem");
+
+  ast::MemberAccessorExpression expr(std::move(str), std::move(mem));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  ASSERT_TRUE(g.EmitExpression(&expr)) << g.error();
+  EXPECT_EQ(g.result(), "str.mem");
+}
+
+}  // namespace
+}  // namespace hlsl
+}  // namespace writer
+}  // namespace tint