Emit case statement

This CL adds case statements to the WGSL generator.

Bug: tint:4
Change-Id: Ic7945646d79b7c3e9e1cb1cf57d1633a28f45fc0
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17180
Reviewed-by: David Neto <dneto@google.com>

src/CMakeLists.txt

@@ -410,6 +410,7 @@ if(${TINT_BUILD_WGSL_WRITER})
     writer/wgsl/generator_impl_assign_test.cc
     writer/wgsl/generator_impl_break_test.cc
     writer/wgsl/generator_impl_call_test.cc
+    writer/wgsl/generator_impl_case_test.cc
     writer/wgsl/generator_impl_cast_test.cc
     writer/wgsl/generator_impl_entry_point_test.cc
     writer/wgsl/generator_impl_identifier_test.cc

src/writer/wgsl/generator_impl.cc

@@ -25,6 +25,7 @@
 #include "src/ast/break_statement.h"
 #include "src/ast/builtin_decoration.h"
 #include "src/ast/call_expression.h"
+#include "src/ast/case_statement.h"
 #include "src/ast/cast_expression.h"
 #include "src/ast/const_initializer_expression.h"
 #include "src/ast/decorated_variable.h"
@@ -274,7 +275,10 @@ bool GeneratorImpl::EmitTypeInitializer(ast::TypeInitializerExpression* expr) {
 
 bool GeneratorImpl::EmitConstInitializer(
     ast::ConstInitializerExpression* expr) {
-  auto lit = expr->literal();
+  return EmitLiteral(expr->literal());
+}
+
+bool GeneratorImpl::EmitLiteral(ast::Literal* lit) {
   if (lit->IsBool()) {
     out_ << (lit->AsBool()->IsTrue() ? "true" : "false");
   } else if (lit->IsFloat()) {
@@ -649,6 +653,9 @@ bool GeneratorImpl::EmitStatement(ast::Statement* stmt) {
   if (stmt->IsBreak()) {
     return EmitBreak(stmt->AsBreak());
   }
+  if (stmt->IsCase()) {
+    return EmitCase(stmt->AsCase());
+  }
 
   error_ = "unknown statement type";
   return false;
@@ -667,7 +674,7 @@ bool GeneratorImpl::EmitAssign(ast::AssignmentStatement* stmt) {
     return false;
   }
 
-  out_ << ";";
+  out_ << ";" << std::endl;
 
   return true;
 }
@@ -692,7 +699,36 @@ bool GeneratorImpl::EmitBreak(ast::BreakStatement* stmt) {
     out_ << ")";
   }
 
-  out_ << ";";
+  out_ << ";" << std::endl;
+
+  return true;
+}
+
+bool GeneratorImpl::EmitCase(ast::CaseStatement* stmt) {
+  make_indent();
+
+  if (stmt->IsDefault()) {
+    out_ << "default:";
+  } else {
+    out_ << "case ";
+
+    if (!EmitLiteral(stmt->condition())) {
+      return false;
+    }
+    out_ << ":";
+  }
+  out_ << " {" << std::endl;
+  increment_indent();
+
+  for (const auto& b : stmt->body()) {
+    if (!EmitStatement(b.get())) {
+      return false;
+    }
+  }
+  decrement_indent();
+
+  make_indent();
+  out_ << "}" << std::endl;
 
   return true;
 }

src/writer/wgsl/generator_impl.h

@@ -90,6 +90,10 @@ class GeneratorImpl {
   /// @param expr the call expression
   /// @returns true if the call expression is emitted
   bool EmitCall(ast::CallExpression* expr);
+  /// Handles a case statement
+  /// @param stmt the statement
+  /// @returns true if the statment was emitted successfully
+  bool EmitCase(ast::CaseStatement* stmt);
   /// Handles generating a cast expression
   /// @param expr the cast expression
   /// @returns true if the cast was emitted
@@ -118,6 +122,10 @@ class GeneratorImpl {
   /// @param expr the initializer expression
   /// @returns true if the expression was emitted
   bool EmitInitializer(ast::InitializerExpression* expr);
+  /// Handles a literal
+  /// @param lit the literal to emit
+  /// @returns true if the literal was successfully emitted
+  bool EmitLiteral(ast::Literal* lit);
   /// Handles a member accessor expression
   /// @param expr the member accessor expression
   /// @returns true if the member accessor was emitted

src/writer/wgsl/generator_impl_assign_test.cc

@@ -36,7 +36,7 @@ TEST_F(GeneratorImplTest, Emit_Assign) {
   g.increment_indent();
 
   ASSERT_TRUE(g.EmitStatement(&assign)) << g.error();
-  EXPECT_EQ(g.result(), "  lhs = rhs;");
+  EXPECT_EQ(g.result(), "  lhs = rhs;\n");
 }
 
 }  // namespace

src/writer/wgsl/generator_impl_break_test.cc

@@ -34,7 +34,7 @@ TEST_F(GeneratorImplTest, Emit_Break) {
   g.increment_indent();
 
   ASSERT_TRUE(g.EmitStatement(&b)) << g.error();
-  EXPECT_EQ(g.result(), "  break;");
+  EXPECT_EQ(g.result(), "  break;\n");
 }
 
 TEST_F(GeneratorImplTest, Emit_BreakWithIf) {
@@ -45,7 +45,7 @@ TEST_F(GeneratorImplTest, Emit_BreakWithIf) {
   g.increment_indent();
 
   ASSERT_TRUE(g.EmitStatement(&b)) << g.error();
-  EXPECT_EQ(g.result(), "  break if (expr);");
+  EXPECT_EQ(g.result(), "  break if (expr);\n");
 }
 
 TEST_F(GeneratorImplTest, Emit_BreakWithUnless) {
@@ -56,7 +56,7 @@ TEST_F(GeneratorImplTest, Emit_BreakWithUnless) {
   g.increment_indent();
 
   ASSERT_TRUE(g.EmitStatement(&b)) << g.error();
-  EXPECT_EQ(g.result(), "  break unless (expr);");
+  EXPECT_EQ(g.result(), "  break unless (expr);\n");
 }
 
 }  // namespace

src/writer/wgsl/generator_impl_case_test.cc

@@ -0,0 +1,71 @@
+// 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/break_statement.h"
+#include "src/ast/case_statement.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/int_literal.h"
+#include "src/writer/wgsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace wgsl {
+namespace {
+
+using GeneratorImplTest = testing::Test;
+
+TEST_F(GeneratorImplTest, Emit_Case) {
+  auto cond = std::make_unique<ast::IntLiteral>(5);
+
+  std::vector<std::unique_ptr<ast::Statement>> body;
+  body.push_back(std::make_unique<ast::BreakStatement>());
+
+  ast::CaseStatement c(std::move(cond), std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5: {
+    break;
+  }
+)");
+}
+
+TEST_F(GeneratorImplTest, Emit_Case_Default) {
+  ast::CaseStatement c;
+
+  std::vector<std::unique_ptr<ast::Statement>> body;
+  body.push_back(std::make_unique<ast::BreakStatement>());
+
+  c.set_body(std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  default: {
+    break;
+  }
+)");
+}
+
+}  // namespace
+}  // namespace wgsl
+}  // namespace writer
+}  // namespace tint