Emit else statements.

This Cl updates the WGSL writer to generate else statements.

Bug: tint:4
Change-Id: I72f6bbb6a2ab00bec3933083fd12c5da1a3dd5f8
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17285
Reviewed-by: David Neto <dneto@google.com>

src/CMakeLists.txt

@@ -413,6 +413,7 @@ if(${TINT_BUILD_WGSL_WRITER})
     writer/wgsl/generator_impl_case_test.cc
     writer/wgsl/generator_impl_cast_test.cc
     writer/wgsl/generator_impl_continue_test.cc
+    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_identifier_test.cc

src/writer/wgsl/generator_impl.cc

@@ -20,6 +20,7 @@
 #include "src/ast/array_accessor_expression.h"
 #include "src/ast/as_expression.h"
 #include "src/ast/assignment_statement.h"
+#include "src/ast/else_statement.h"
 #include "src/ast/binding_decoration.h"
 #include "src/ast/bool_literal.h"
 #include "src/ast/break_statement.h"
@@ -660,9 +661,6 @@ bool GeneratorImpl::EmitStatement(ast::Statement* stmt) {
   if (stmt->IsBreak()) {
     return EmitBreak(stmt->AsBreak());
   }
-  if (stmt->IsCase()) {
-    return EmitCase(stmt->AsCase());
-  }
   if (stmt->IsContinue()) {
     return EmitContinue(stmt->AsContinue());
   }
@@ -795,6 +793,34 @@ bool GeneratorImpl::EmitContinue(ast::ContinueStatement* stmt) {
   return true;
 }
 
+bool GeneratorImpl::EmitElse(ast::ElseStatement* stmt) {
+  if (stmt->HasCondition()) {
+    out_ << " elseif (";
+    if (!EmitExpression(stmt->condition())) {
+      return false;
+    }
+    out_ << ")";
+  } else {
+    out_ << " else";
+  }
+  out_ << " {" << std::endl;
+
+  increment_indent();
+
+  for (const auto& s : stmt->body()) {
+    if (!EmitStatement(s.get())) {
+      return false;
+    }
+  }
+
+  decrement_indent();
+
+  make_indent();
+  out_ << "}";
+
+  return true;
+}
+
 bool GeneratorImpl::EmitFallthrough(ast::FallthroughStatement*) {
   make_indent();
   out_ << "fallthrough;" << std::endl;

src/writer/wgsl/generator_impl.h

@@ -106,6 +106,10 @@ class GeneratorImpl {
   /// @param stmt the statement to emit
   /// @returns true if the statement was emitted successfully
   bool EmitContinue(ast::ContinueStatement* stmt);
+  /// Handles generating an else statement
+  /// @param stmt the statement to emit
+  /// @returns true if the statement was emitted
+  bool EmitElse(ast::ElseStatement* stmt);
   /// Handles generating an entry_point command
   /// @param ep the entry point
   /// @returns true if the entry point was emitted

src/writer/wgsl/generator_impl_case_test.cc

@@ -40,7 +40,7 @@ TEST_F(GeneratorImplTest, Emit_Case) {
   GeneratorImpl g;
   g.increment_indent();
 
-  ASSERT_TRUE(g.EmitStatement(&c)) << g.error();
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
   EXPECT_EQ(g.result(), R"(  case 5: {
     break;
   }
@@ -58,7 +58,7 @@ TEST_F(GeneratorImplTest, Emit_Case_Default) {
   GeneratorImpl g;
   g.increment_indent();
 
-  ASSERT_TRUE(g.EmitStatement(&c)) << g.error();
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
   EXPECT_EQ(g.result(), R"(  default: {
     break;
   }

src/writer/wgsl/generator_impl_else_test.cc

@@ -0,0 +1,67 @@
+// 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/kill_statement.h"
+#include "src/ast/else_statement.h"
+#include "src/ast/identifier_expression.h"
+#include "src/writer/wgsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace wgsl {
+namespace {
+
+using GeneratorImplTest = testing::Test;
+
+TEST_F(GeneratorImplTest, Emit_Else) {
+  std::vector<std::unique_ptr<ast::Statement>> body;
+  body.push_back(std::make_unique<ast::KillStatement>());
+
+  ast::ElseStatement e(std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitElse(&e)) << g.error();
+  EXPECT_EQ(g.result(), R"( else {
+    kill;
+  })");
+}
+
+TEST_F(GeneratorImplTest, Emit_ElseWithCondition) {
+  auto cond = std::make_unique<ast::IdentifierExpression>("cond");
+
+  std::vector<std::unique_ptr<ast::Statement>> body;
+  body.push_back(std::make_unique<ast::KillStatement>());
+
+  ast::ElseStatement e(std::move(cond), std::move(body));
+
+  GeneratorImpl g;
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitElse(&e)) << g.error();
+  EXPECT_EQ(g.result(), R"( elseif (cond) {
+    kill;
+  })");
+}
+
+}  // namespace
+}  // namespace wgsl
+}  // namespace writer
+}  // namespace tint
+