Emit functions.

This Cl adds functions to the WGSL generator.

Bug: tint:4
Change-Id: Ibc7d27597c6c0d63c82931d0fa016856359d21b5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17340
Reviewed-by: David Neto <dneto@google.com>

src/CMakeLists.txt

@@ -416,6 +416,7 @@ if(${TINT_BUILD_WGSL_WRITER})
     writer/wgsl/generator_impl_else_test.cc
     writer/wgsl/generator_impl_entry_point_test.cc
     writer/wgsl/generator_impl_fallthrough_test.cc
+    writer/wgsl/generator_impl_function_test.cc
     writer/wgsl/generator_impl_identifier_test.cc
     writer/wgsl/generator_impl_if_test.cc
     writer/wgsl/generator_impl_import_test.cc

src/writer/wgsl/generator_impl.cc

@@ -104,6 +104,13 @@ bool GeneratorImpl::Generate(const ast::Module& module) {
     out_ << std::endl;
   }
 
+  for (const auto& func : module.functions()) {
+    if (!EmitFunction(func.get())) {
+      return false;
+    }
+    out_ << std::endl;
+  }
+
   return true;
 }
 
@@ -331,6 +338,48 @@ bool GeneratorImpl::EmitImport(const ast::Import* import) {
   return true;
 }
 
+bool GeneratorImpl::EmitFunction(ast::Function* func) {
+  make_indent();
+
+  out_ << "fn " << func->name() << "(";
+
+  bool first = true;
+  for (const auto& v : func->params()) {
+    if (!first) {
+      out_ << ", ";
+    }
+    first = false;
+
+    out_ << v->name() << " : ";
+
+    if (!EmitType(v->type())) {
+      return false;
+    }
+  }
+
+  out_ << ") -> ";
+
+  if (!EmitType(func->return_type())) {
+    return false;
+  }
+
+  out_ << " {" << std::endl;
+
+  increment_indent();
+
+  for (const auto& s : func->body()) {
+    if (!EmitStatement(s.get())) {
+      return false;
+    }
+  }
+
+  decrement_indent();
+  make_indent();
+  out_ << "}" << std::endl;
+
+  return true;
+}
+
 bool GeneratorImpl::EmitType(ast::type::Type* type) {
   if (type->IsAlias()) {
     auto alias = type->AsAlias();

src/writer/wgsl/generator_impl.h

@@ -122,6 +122,10 @@ class GeneratorImpl {
   /// @param stmt the fallthrough statement
   /// @returns true if the statement was successfully emitted
   bool EmitFallthrough(ast::FallthroughStatement* stmt);
+  /// Handles generating a function
+  /// @param func the function to generate
+  /// @returns true if the function was emitted
+  bool EmitFunction(ast::Function* func);
   /// Handles generating an identifier expression
   /// @param expr the identifier expression
   /// @returns true if the identifeir was emitted

src/writer/wgsl/generator_impl_function_test.cc

@@ -0,0 +1,83 @@
+// 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/function.h"
+#include "src/ast/kill_statement.h"
+#include "src/ast/return_statement.h"
+#include "src/ast/type/f32_type.h"
+#include "src/ast/type/i32_type.h"
+#include "src/ast/type/void_type.h"
+#include "src/ast/variable.h"
+#include "src/writer/wgsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace wgsl {
+namespace {
+
+using GeneratorImplTest = testing::Test;
+
+TEST_F(GeneratorImplTest, Emit_Function) {
+  std::vector<std::unique_ptr<ast::Statement>> body;
+  body.push_back(std::make_unique<ast::KillStatement>());
+  body.push_back(std::make_unique<ast::ReturnStatement>());
+
+  ast::type::VoidType void_type;
+  ast::Function func("my_func", {}, &void_type);
+  func.set_body(std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitFunction(&func));
+  EXPECT_EQ(g.result(), R"(  fn my_func() -> void {
+    kill;
+    return;
+  }
+)");
+}
+
+TEST_F(GeneratorImplTest, Emit_Function_WithParams) {
+  std::vector<std::unique_ptr<ast::Statement>> body;
+  body.push_back(std::make_unique<ast::KillStatement>());
+  body.push_back(std::make_unique<ast::ReturnStatement>());
+
+  ast::type::F32Type f32;
+  ast::type::I32Type i32;
+  std::vector<std::unique_ptr<ast::Variable>> params;
+  params.push_back(
+      std::make_unique<ast::Variable>("a", ast::StorageClass::kNone, &f32));
+  params.push_back(
+      std::make_unique<ast::Variable>("b", ast::StorageClass::kNone, &i32));
+
+  ast::type::VoidType void_type;
+  ast::Function func("my_func", std::move(params), &void_type);
+  func.set_body(std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitFunction(&func));
+  EXPECT_EQ(g.result(), R"(  fn my_func(a : f32, b : i32) -> void {
+    kill;
+    return;
+  }
+)");
+}
+
+}  // namespace
+}  // namespace wgsl
+}  // namespace writer
+}  // namespace tint