[hlsl-writer] Add if/else statements.

This CL adds if/else statement emission to the HLSL writer.

Bug: tint:7
Change-Id: Idd6e6d8c329ed270676fa0276474a68c715dd9eb
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/25847
Reviewed-by: David Neto <dneto@google.com>

BUILD.gn

@@ -1053,6 +1053,7 @@ source_set("tint_unittests_hlsl_writer_src") {
     "src/writer/hlsl/generator_impl_continue_test.cc",
     "src/writer/hlsl/generator_impl_discard_test.cc",
     "src/writer/hlsl/generator_impl_identifier_test.cc",
+    "src/writer/hlsl/generator_impl_if_test.cc",
     "src/writer/hlsl/generator_impl_member_accessor_test.cc",
     "src/writer/hlsl/generator_impl_return_test.cc",
     "src/writer/hlsl/generator_impl_switch_test.cc",

src/CMakeLists.txt

@@ -561,6 +561,7 @@ if (${TINT_BUILD_HLSL_WRITER})
     writer/hlsl/generator_impl_continue_test.cc
     writer/hlsl/generator_impl_discard_test.cc
     writer/hlsl/generator_impl_identifier_test.cc
+    writer/hlsl/generator_impl_if_test.cc
     writer/hlsl/generator_impl_member_accessor_test.cc
     writer/hlsl/generator_impl_return_test.cc
     writer/hlsl/generator_impl_switch_test.cc

src/writer/hlsl/generator_impl.cc

@@ -20,8 +20,10 @@
 #include "src/ast/binary_expression.h"
 #include "src/ast/bool_literal.h"
 #include "src/ast/case_statement.h"
+#include "src/ast/else_statement.h"
 #include "src/ast/float_literal.h"
 #include "src/ast/identifier_expression.h"
+#include "src/ast/if_statement.h"
 #include "src/ast/member_accessor_expression.h"
 #include "src/ast/return_statement.h"
 #include "src/ast/sint_literal.h"
@@ -447,6 +449,43 @@ bool GeneratorImpl::EmitIdentifier(ast::IdentifierExpression* expr) {
   return true;
 }
 
+bool GeneratorImpl::EmitIf(ast::IfStatement* stmt) {
+  make_indent();
+
+  out_ << "if (";
+  if (!EmitExpression(stmt->condition())) {
+    return false;
+  }
+  out_ << ") ";
+
+  if (!EmitBlock(stmt->body())) {
+    return false;
+  }
+
+  for (const auto& e : stmt->else_statements()) {
+    if (!EmitElse(e.get())) {
+      return false;
+    }
+  }
+  out_ << std::endl;
+
+  return true;
+}
+
+bool GeneratorImpl::EmitElse(ast::ElseStatement* stmt) {
+  if (stmt->HasCondition()) {
+    out_ << " else if (";
+    if (!EmitExpression(stmt->condition())) {
+      return false;
+    }
+    out_ << ") ";
+  } else {
+    out_ << " else ";
+  }
+
+  return EmitBlock(stmt->body());
+}
+
 bool GeneratorImpl::EmitLiteral(ast::Literal* lit) {
   if (lit->IsBool()) {
     out_ << (lit->AsBool()->IsTrue() ? "true" : "false");
@@ -539,6 +578,9 @@ bool GeneratorImpl::EmitStatement(ast::Statement* stmt) {
     out_ << "/* fallthrough */" << std::endl;
     return true;
   }
+  if (stmt->IsIf()) {
+    return EmitIf(stmt->AsIf());
+  }
   if (stmt->IsReturn()) {
     return EmitReturn(stmt->AsReturn());
   }

src/writer/hlsl/generator_impl.h

@@ -98,10 +98,18 @@ class GeneratorImpl : public TextGenerator {
   /// @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 generate an Expression
   /// @param expr the expression
   /// @returns true if the expression was emitted
   bool EmitExpression(ast::Expression* expr);
+  /// Handles an if statement
+  /// @param stmt the statement to emit
+  /// @returns true if the statement was successfully emitted
+  bool EmitIf(ast::IfStatement* stmt);
   /// Handles a literal
   /// @param lit the literal to emit
   /// @returns true if the literal was successfully emitted

src/writer/hlsl/generator_impl_if_test.cc

@@ -0,0 +1,143 @@
+// 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/else_statement.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/if_statement.h"
+#include "src/ast/module.h"
+#include "src/ast/return_statement.h"
+#include "src/writer/hlsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace hlsl {
+namespace {
+
+using HlslGeneratorImplTest = testing::Test;
+
+TEST_F(HlslGeneratorImplTest, Emit_If) {
+  auto cond = std::make_unique<ast::IdentifierExpression>("cond");
+  auto body = std::make_unique<ast::BlockStatement>();
+  body->append(std::make_unique<ast::ReturnStatement>());
+
+  ast::IfStatement i(std::move(cond), std::move(body));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&i)) << g.error();
+  EXPECT_EQ(g.result(), R"(  if (cond) {
+    return;
+  }
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, Emit_IfWithElseIf) {
+  auto else_cond = std::make_unique<ast::IdentifierExpression>("else_cond");
+  auto else_body = std::make_unique<ast::BlockStatement>();
+  else_body->append(std::make_unique<ast::ReturnStatement>());
+
+  ast::ElseStatementList elses;
+  elses.push_back(std::make_unique<ast::ElseStatement>(std::move(else_cond),
+                                                       std::move(else_body)));
+
+  auto cond = std::make_unique<ast::IdentifierExpression>("cond");
+  auto body = std::make_unique<ast::BlockStatement>();
+  body->append(std::make_unique<ast::ReturnStatement>());
+
+  ast::IfStatement i(std::move(cond), std::move(body));
+  i.set_else_statements(std::move(elses));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&i)) << g.error();
+  EXPECT_EQ(g.result(), R"(  if (cond) {
+    return;
+  } else if (else_cond) {
+    return;
+  }
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, Emit_IfWithElse) {
+  auto else_body = std::make_unique<ast::BlockStatement>();
+  else_body->append(std::make_unique<ast::ReturnStatement>());
+
+  ast::ElseStatementList elses;
+  elses.push_back(std::make_unique<ast::ElseStatement>(std::move(else_body)));
+
+  auto cond = std::make_unique<ast::IdentifierExpression>("cond");
+  auto body = std::make_unique<ast::BlockStatement>();
+  body->append(std::make_unique<ast::ReturnStatement>());
+
+  ast::IfStatement i(std::move(cond), std::move(body));
+  i.set_else_statements(std::move(elses));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&i)) << g.error();
+  EXPECT_EQ(g.result(), R"(  if (cond) {
+    return;
+  } else {
+    return;
+  }
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, Emit_IfWithMultiple) {
+  auto else_cond = std::make_unique<ast::IdentifierExpression>("else_cond");
+
+  auto else_body = std::make_unique<ast::BlockStatement>();
+  else_body->append(std::make_unique<ast::ReturnStatement>());
+
+  auto else_body_2 = std::make_unique<ast::BlockStatement>();
+  else_body_2->append(std::make_unique<ast::ReturnStatement>());
+
+  ast::ElseStatementList elses;
+  elses.push_back(std::make_unique<ast::ElseStatement>(std::move(else_cond),
+                                                       std::move(else_body)));
+  elses.push_back(std::make_unique<ast::ElseStatement>(std::move(else_body_2)));
+
+  auto cond = std::make_unique<ast::IdentifierExpression>("cond");
+  auto body = std::make_unique<ast::BlockStatement>();
+  body->append(std::make_unique<ast::ReturnStatement>());
+
+  ast::IfStatement i(std::move(cond), std::move(body));
+  i.set_else_statements(std::move(elses));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&i)) << g.error();
+  EXPECT_EQ(g.result(), R"(  if (cond) {
+    return;
+  } else if (else_cond) {
+    return;
+  } else {
+    return;
+  }
+)");
+}
+
+}  // namespace
+}  // namespace hlsl
+}  // namespace writer
+}  // namespace tint