[msl-writer] Add variable declarations.

This CL adds variable declarations to the MSL backend.

Bug: tint:7
Change-Id: Icf63ad44a217213e5036eb76429e25a3031822eb
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/24540
Reviewed-by: David Neto <dneto@google.com>

src/CMakeLists.txt

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0776647..66ae755 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -515,6 +515,7 @@
     writer/msl/generator_impl_test.cc
     writer/msl/generator_impl_type_test.cc
     writer/msl/generator_impl_unary_op_test.cc
+    writer/msl/generator_impl_variable_decl_statement_test.cc
     writer/msl/namer_test.cc
   )
 endif()

src/writer/msl/generator_impl.cc

diff --git a/src/writer/msl/generator_impl.cc b/src/writer/msl/generator_impl.cc
index 70b78fe..2468a3b 100644
--- a/src/writer/msl/generator_impl.cc
+++ b/src/writer/msl/generator_impl.cc
@@ -46,6 +46,7 @@
 #include "src/ast/type/void_type.h"
 #include "src/ast/uint_literal.h"
 #include "src/ast/unary_op_expression.h"
+#include "src/ast/variable_decl_statement.h"
 
 namespace tint {
 namespace writer {
@@ -314,22 +315,48 @@
 
   out_ << "(";
 
-  bool first = true;
-  for (const auto& e : expr->values()) {
-    if (!first) {
-      out_ << ", ";
-    }
-    first = false;
-
-    if (!EmitExpression(e.get())) {
+  // If the type constructor is empty then we need to construct with the zero
+  // value for all components.
+  if (expr->values().empty()) {
+    if (!EmitZeroValue(expr->type())) {
       return false;
     }
+  } else {
+    bool first = true;
+    for (const auto& e : expr->values()) {
+      if (!first) {
+        out_ << ", ";
+      }
+      first = false;
+
+      if (!EmitExpression(e.get())) {
+        return false;
+      }
+    }
   }
 
   out_ << ")";
   return true;
 }
 
+bool GeneratorImpl::EmitZeroValue(ast::type::Type* type) {
+  if (type->IsBool()) {
+    out_ << "false";
+  } else if (type->IsF32()) {
+    out_ << "0.0f";
+  } else if (type->IsI32()) {
+    out_ << "0";
+  } else if (type->IsU32()) {
+    out_ << "0u";
+  } else if (type->IsVector()) {
+    return EmitZeroValue(type->AsVector()->type());
+  } else {
+    error_ = "Invalid type for zero emission: " + type->type_name();
+    return false;
+  }
+  return true;
+}
+
 bool GeneratorImpl::EmitScalarConstructor(
     ast::ScalarConstructorExpression* expr) {
   return EmitLiteral(expr->literal());
@@ -647,6 +674,9 @@
   if (stmt->IsSwitch()) {
     return EmitSwitch(stmt->AsSwitch());
   }
+  if (stmt->IsVariableDecl()) {
+    return EmitVariable(stmt->AsVariableDecl()->variable());
+  }
 
   error_ = "unknown statement type: " + stmt->str();
   return false;
@@ -781,6 +811,36 @@
   return true;
 }
 
+bool GeneratorImpl::EmitVariable(ast::Variable* var) {
+  make_indent();
+
+  // TODO(dsinclair): Handle variable decorations
+  if (var->IsDecorated()) {
+    error_ = "Variable decorations are not handled yet";
+    return false;
+  }
+
+  if (var->is_const()) {
+    out_ << "const ";
+  }
+  if (!EmitType(var->type(), var->name())) {
+    return false;
+  }
+  if (!var->type()->IsArray()) {
+    out_ << " " << var->name();
+  }
+
+  if (var->constructor() != nullptr) {
+    out_ << " = ";
+    if (!EmitExpression(var->constructor())) {
+      return false;
+    }
+  }
+  out_ << ";" << std::endl;
+
+  return true;
+}
+
 }  // namespace msl
 }  // namespace writer
 }  // namespace tint

src/writer/msl/generator_impl.h

diff --git a/src/writer/msl/generator_impl.h b/src/writer/msl/generator_impl.h
index 7e2448c..719e1c3 100644
--- a/src/writer/msl/generator_impl.h
+++ b/src/writer/msl/generator_impl.h
@@ -157,6 +157,14 @@
   /// @param expr the expression to emit
   /// @returns true if the expression was emitted
   bool EmitUnaryOp(ast::UnaryOpExpression* expr);
+  /// Handles generating a variable
+  /// @param var the variable to generate
+  /// @returns true if the variable was emitted
+  bool EmitVariable(ast::Variable* var);
+  /// Emits the zero value for the given type
+  /// @param type the type to emit the value for
+  /// @returns true if the zero value was successfully emitted.
+  bool EmitZeroValue(ast::type::Type* type);
 
  private:
   Namer namer_;

src/writer/msl/generator_impl_constructor_test.cc

diff --git a/src/writer/msl/generator_impl_constructor_test.cc b/src/writer/msl/generator_impl_constructor_test.cc
index 2ebf533..ba2518d 100644
--- a/src/writer/msl/generator_impl_constructor_test.cc
+++ b/src/writer/msl/generator_impl_constructor_test.cc
@@ -157,6 +157,18 @@
   EXPECT_EQ(g.result(), "float3(1.00000000f, 2.00000000f, 3.00000000f)");
 }
 
+TEST_F(MslGeneratorImplTest, EmitConstructor_Type_Vec_Empty) {
+  ast::type::F32Type f32;
+  ast::type::VectorType vec(&f32, 3);
+
+  ast::ExpressionList values;
+  ast::TypeConstructorExpression expr(&vec, std::move(values));
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitConstructor(&expr)) << g.error();
+  EXPECT_EQ(g.result(), "float3(0.0f)");
+}
+
 TEST_F(MslGeneratorImplTest, EmitConstructor_Type_Mat) {
   ast::type::F32Type f32;
   ast::type::MatrixType mat(&f32, 3, 2);

src/writer/msl/generator_impl_variable_decl_statement_test.cc

diff --git a/src/writer/msl/generator_impl_variable_decl_statement_test.cc b/src/writer/msl/generator_impl_variable_decl_statement_test.cc
new file mode 100644
index 0000000..1f99714
--- /dev/null
+++ b/src/writer/msl/generator_impl_variable_decl_statement_test.cc
@@ -0,0 +1,131 @@
+// 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 <vector>
+
+#include "gtest/gtest.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/type/array_type.h"
+#include "src/ast/type/f32_type.h"
+#include "src/ast/type/vector_type.h"
+#include "src/ast/variable.h"
+#include "src/ast/variable_decl_statement.h"
+#include "src/writer/msl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace msl {
+namespace {
+
+using MslGeneratorImplTest = testing::Test;
+
+TEST_F(MslGeneratorImplTest, Emit_VariableDeclStatement) {
+  ast::type::F32Type f32;
+  auto var =
+      std::make_unique<ast::Variable>("a", ast::StorageClass::kNone, &f32);
+
+  ast::VariableDeclStatement stmt(std::move(var));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&stmt)) << g.error();
+  EXPECT_EQ(g.result(), "  float a;\n");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_VariableDeclStatement_Array) {
+  ast::type::F32Type f32;
+  ast::type::ArrayType ary(&f32, 5);
+
+  auto var =
+      std::make_unique<ast::Variable>("a", ast::StorageClass::kNone, &ary);
+
+  ast::VariableDeclStatement stmt(std::move(var));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&stmt)) << g.error();
+  EXPECT_EQ(g.result(), "  float a[5];\n");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_VariableDeclStatement_Function) {
+  ast::type::F32Type f32;
+  auto var =
+      std::make_unique<ast::Variable>("a", ast::StorageClass::kFunction, &f32);
+
+  ast::VariableDeclStatement stmt(std::move(var));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&stmt)) << g.error();
+  EXPECT_EQ(g.result(), "  float a;\n");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_VariableDeclStatement_Private) {
+  ast::type::F32Type f32;
+  auto var =
+      std::make_unique<ast::Variable>("a", ast::StorageClass::kPrivate, &f32);
+
+  ast::VariableDeclStatement stmt(std::move(var));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&stmt)) << g.error();
+  EXPECT_EQ(g.result(), "  float a;\n");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_VariableDeclStatement_Initializer_Private) {
+  auto ident = std::make_unique<ast::IdentifierExpression>("initializer");
+
+  ast::type::F32Type f32;
+  auto var =
+      std::make_unique<ast::Variable>("a", ast::StorageClass::kNone, &f32);
+  var->set_constructor(std::move(ident));
+
+  ast::VariableDeclStatement stmt(std::move(var));
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitStatement(&stmt)) << g.error();
+  EXPECT_EQ(g.result(), R"(float a = initializer;
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_VariableDeclStatement_Initializer_ZeroVec) {
+  ast::type::F32Type f32;
+  ast::type::VectorType vec(&f32, 3);
+
+  ast::ExpressionList values;
+  auto zero_vec =
+      std::make_unique<ast::TypeConstructorExpression>(&vec, std::move(values));
+
+  auto var =
+      std::make_unique<ast::Variable>("a", ast::StorageClass::kNone, &vec);
+  var->set_constructor(std::move(zero_vec));
+
+  ast::VariableDeclStatement stmt(std::move(var));
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitStatement(&stmt)) << g.error();
+  EXPECT_EQ(g.result(), R"(float3 a = float3(0.0f);
+)");
+}
+
+}  // namespace
+}  // namespace msl
+}  // namespace writer
+}  // namespace tint

src/writer/wgsl/generator_impl_variable_decl_statement_test.cc

diff --git a/src/writer/wgsl/generator_impl_variable_decl_statement_test.cc b/src/writer/wgsl/generator_impl_variable_decl_statement_test.cc
index 4f705a4..2e0e03a 100644
--- a/src/writer/wgsl/generator_impl_variable_decl_statement_test.cc
+++ b/src/writer/wgsl/generator_impl_variable_decl_statement_test.cc
@@ -16,6 +16,7 @@
 #include <vector>
 
 #include "gtest/gtest.h"
+#include "src/ast/identifier_expression.h"
 #include "src/ast/type/f32_type.h"
 #include "src/ast/variable.h"
 #include "src/ast/variable_decl_statement.h"