[msl-writer] Emit switch statements.

This CL adds support for switch and case statements into the MSL writer.

Bug: tint:8
Change-Id: Ib51f943e8476c0ecfd45e9131404f96934c6e21f
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/24180
Reviewed-by: David Neto <dneto@google.com>

BUILD.gn

@@ -890,6 +890,7 @@ source_set("tint_unittests_msl_writer_src") {
     "src/writer/msl/generator_impl_assign_test.cc",
     "src/writer/msl/generator_impl_binary_test.cc",
     "src/writer/msl/generator_impl_break_test.cc",
+    "src/writer/msl/generator_impl_case_test.cc",
     "src/writer/msl/generator_impl_cast_test.cc",
     "src/writer/msl/generator_impl_constructor_test.cc",
     "src/writer/msl/generator_impl_continue_test.cc",
@@ -900,6 +901,7 @@ source_set("tint_unittests_msl_writer_src") {
     "src/writer/msl/generator_impl_loop_test.cc",
     "src/writer/msl/generator_impl_member_accessor_test.cc",
     "src/writer/msl/generator_impl_return_test.cc",
+    "src/writer/msl/generator_impl_switch_test.cc",
     "src/writer/msl/generator_impl_test.cc",
     "src/writer/msl/generator_impl_type_test.cc",
     "src/writer/msl/generator_impl_unary_op_test.cc",

src/CMakeLists.txt

@@ -498,6 +498,7 @@ if(${TINT_BUILD_MSL_WRITER})
     writer/msl/generator_impl_assign_test.cc
     writer/msl/generator_impl_binary_test.cc
     writer/msl/generator_impl_break_test.cc
+    writer/msl/generator_impl_case_test.cc
     writer/msl/generator_impl_cast_test.cc
     writer/msl/generator_impl_constructor_test.cc
     writer/msl/generator_impl_continue_test.cc
@@ -508,6 +509,7 @@ if(${TINT_BUILD_MSL_WRITER})
     writer/msl/generator_impl_loop_test.cc
     writer/msl/generator_impl_member_accessor_test.cc
     writer/msl/generator_impl_return_test.cc
+    writer/msl/generator_impl_switch_test.cc
     writer/msl/generator_impl_test.cc
     writer/msl/generator_impl_type_test.cc
     writer/msl/generator_impl_unary_op_test.cc

src/writer/msl/generator_impl.cc

@@ -20,6 +20,7 @@
 #include "src/ast/binary_expression.h"
 #include "src/ast/bool_literal.h"
 #include "src/ast/break_statement.h"
+#include "src/ast/case_statement.h"
 #include "src/ast/cast_expression.h"
 #include "src/ast/continue_statement.h"
 #include "src/ast/else_statement.h"
@@ -31,6 +32,7 @@
 #include "src/ast/member_accessor_expression.h"
 #include "src/ast/return_statement.h"
 #include "src/ast/sint_literal.h"
+#include "src/ast/switch_statement.h"
 #include "src/ast/type/alias_type.h"
 #include "src/ast/type/array_type.h"
 #include "src/ast/type/bool_type.h"
@@ -48,6 +50,17 @@
 namespace tint {
 namespace writer {
 namespace msl {
+namespace {
+
+bool last_is_break_or_fallthrough(const ast::StatementList& stmts) {
+  if (stmts.empty()) {
+    return false;
+  }
+
+  return stmts.back()->IsBreak() || stmts.back()->IsFallthrough();
+}
+
+}  // namespace
 
 GeneratorImpl::GeneratorImpl() = default;
 
@@ -222,6 +235,50 @@ bool GeneratorImpl::EmitBreak(ast::BreakStatement*) {
   return true;
 }
 
+bool GeneratorImpl::EmitCase(ast::CaseStatement* stmt) {
+  make_indent();
+
+  if (stmt->IsDefault()) {
+    out_ << "default:";
+  } else {
+    bool first = true;
+    for (const auto& selector : stmt->selectors()) {
+      if (!first) {
+        out_ << std::endl;
+        make_indent();
+      }
+      first = false;
+
+      out_ << "case ";
+      if (!EmitLiteral(selector.get())) {
+        return false;
+      }
+      out_ << ":";
+    }
+  }
+
+  out_ << " {" << std::endl;
+
+  increment_indent();
+
+  for (const auto& s : stmt->body()) {
+    if (!EmitStatement(s.get())) {
+      return false;
+    }
+  }
+
+  if (!last_is_break_or_fallthrough(stmt->body())) {
+    make_indent();
+    out_ << "break;" << std::endl;
+  }
+
+  decrement_indent();
+  make_indent();
+  out_ << "}" << std::endl;
+
+  return true;
+}
+
 bool GeneratorImpl::EmitCast(ast::CastExpression* expr) {
   if (!EmitType(expr->type(), "")) {
     return false;
@@ -567,6 +624,11 @@ bool GeneratorImpl::EmitStatement(ast::Statement* stmt) {
   if (stmt->IsContinue()) {
     return EmitContinue(stmt->AsContinue());
   }
+  if (stmt->IsFallthrough()) {
+    make_indent();
+    out_ << "/* fallthrough */" << std::endl;
+    return true;
+  }
   if (stmt->IsIf()) {
     return EmitIf(stmt->AsIf());
   }
@@ -579,11 +641,38 @@ bool GeneratorImpl::EmitStatement(ast::Statement* stmt) {
   if (stmt->IsReturn()) {
     return EmitReturn(stmt->AsReturn());
   }
+  if (stmt->IsSwitch()) {
+    return EmitSwitch(stmt->AsSwitch());
+  }
 
   error_ = "unknown statement type";
   return false;
 }
 
+bool GeneratorImpl::EmitSwitch(ast::SwitchStatement* stmt) {
+  make_indent();
+
+  out_ << "switch(";
+  if (!EmitExpression(stmt->condition())) {
+    return false;
+  }
+  out_ << ") {" << std::endl;
+
+  increment_indent();
+
+  for (const auto& s : stmt->body()) {
+    if (!EmitCase(s.get())) {
+      return false;
+    }
+  }
+
+  decrement_indent();
+  make_indent();
+  out_ << "}" << std::endl;
+
+  return true;
+}
+
 bool GeneratorImpl::EmitType(ast::type::Type* type, const std::string& name) {
   if (type->IsAlias()) {
     auto* alias = type->AsAlias();

src/writer/msl/generator_impl.h

@@ -64,6 +64,10 @@ class GeneratorImpl : public TextGenerator {
   /// @param stmt the statement to emit
   /// @returns true if the statement was emitted successfully
   bool EmitBreak(ast::BreakStatement* stmt);
+  /// 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
@@ -135,6 +139,10 @@ class GeneratorImpl : public TextGenerator {
   /// @param stmt the statement to emit
   /// @returns true if the statement was emitted
   bool EmitStatement(ast::Statement* stmt);
+  /// Handles generating a switch statement
+  /// @param stmt the statement to emit
+  /// @returns true if the statement was emitted
+  bool EmitSwitch(ast::SwitchStatement* stmt);
   /// Handles generating type
   /// @param type the type to generate
   /// @param name the name of the variable, only used for array emission

src/writer/msl/generator_impl_case_test.cc

@@ -0,0 +1,135 @@
+// 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/break_statement.h"
+#include "src/ast/case_statement.h"
+#include "src/ast/fallthrough_statement.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/sint_literal.h"
+#include "src/ast/type/i32_type.h"
+#include "src/writer/msl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace msl {
+namespace {
+
+using MslGeneratorImplTest = testing::Test;
+
+TEST_F(MslGeneratorImplTest, Emit_Case) {
+  ast::type::I32Type i32;
+
+  ast::StatementList body;
+  body.push_back(std::make_unique<ast::BreakStatement>());
+
+  ast::CaseSelectorList lit;
+  lit.push_back(std::make_unique<ast::SintLiteral>(&i32, 5));
+  ast::CaseStatement c(std::move(lit), std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5: {
+    break;
+  }
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_Case_BreaksByDefault) {
+  ast::type::I32Type i32;
+
+  ast::StatementList body;
+
+  ast::CaseSelectorList lit;
+  lit.push_back(std::make_unique<ast::SintLiteral>(&i32, 5));
+  ast::CaseStatement c(std::move(lit), std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5: {
+    break;
+  }
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_Case_WithFallthrough) {
+  ast::type::I32Type i32;
+
+  ast::StatementList body;
+  body.push_back(std::make_unique<ast::FallthroughStatement>());
+
+  ast::CaseSelectorList lit;
+  lit.push_back(std::make_unique<ast::SintLiteral>(&i32, 5));
+  ast::CaseStatement c(std::move(lit), std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5: {
+    /* fallthrough */
+  }
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_Case_MultipleSelectors) {
+  ast::type::I32Type i32;
+
+  ast::StatementList body;
+  body.push_back(std::make_unique<ast::BreakStatement>());
+
+  ast::CaseSelectorList lit;
+  lit.push_back(std::make_unique<ast::SintLiteral>(&i32, 5));
+  lit.push_back(std::make_unique<ast::SintLiteral>(&i32, 6));
+  ast::CaseStatement c(std::move(lit), std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5:
+  case 6: {
+    break;
+  }
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_Case_Default) {
+  ast::CaseStatement c;
+
+  ast::StatementList body;
+  body.push_back(std::make_unique<ast::BreakStatement>());
+
+  c.set_body(std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  default: {
+    break;
+  }
+)");
+}
+
+}  // namespace
+}  // namespace msl
+}  // namespace writer
+}  // namespace tint

src/writer/msl/generator_impl_switch_test.cc

@@ -0,0 +1,74 @@
+// 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/break_statement.h"
+#include "src/ast/case_statement.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/sint_literal.h"
+#include "src/ast/switch_statement.h"
+#include "src/ast/type/i32_type.h"
+#include "src/writer/msl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace msl {
+namespace {
+
+using MslGeneratorImplTest = testing::Test;
+
+TEST_F(MslGeneratorImplTest, Emit_Switch) {
+  auto def = std::make_unique<ast::CaseStatement>();
+  ast::StatementList def_body;
+  def_body.push_back(std::make_unique<ast::BreakStatement>());
+  def->set_body(std::move(def_body));
+
+  ast::type::I32Type i32;
+  ast::CaseSelectorList case_val;
+  case_val.push_back(std::make_unique<ast::SintLiteral>(&i32, 5));
+
+  ast::StatementList case_body;
+  case_body.push_back(std::make_unique<ast::BreakStatement>());
+
+  auto case_stmt = std::make_unique<ast::CaseStatement>(std::move(case_val),
+                                                        std::move(case_body));
+
+  ast::CaseStatementList body;
+  body.push_back(std::move(case_stmt));
+  body.push_back(std::move(def));
+
+  auto cond = std::make_unique<ast::IdentifierExpression>("cond");
+  ast::SwitchStatement s(std::move(cond), std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&s)) << g.error();
+  EXPECT_EQ(g.result(), R"(  switch(cond) {
+    case 5: {
+      break;
+    }
+    default: {
+      break;
+    }
+  }
+)");
+}
+
+}  // namespace
+}  // namespace msl
+}  // namespace writer
+}  // namespace tint