[hlsl-writer] Emit case statements.

This CL adds emission of case statements to the HLSL backend.

Bug: tint:7
Change-Id: I5d0dd7ecfe4ef032a03777c29f3d0d00e584a93a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/25222
Reviewed-by: David Neto <dneto@google.com>

BUILD.gn

@@ -1020,6 +1020,7 @@ source_set("tint_unittests_hlsl_writer_src") {
   sources = [
     "src/writer/hlsl/generator_impl_binary_test.cc",
     "src/writer/hlsl/generator_impl_break_test.cc",
+    "src/writer/hlsl/generator_impl_case_test.cc",
     "src/writer/hlsl/generator_impl_continue_test.cc",
     "src/writer/hlsl/generator_impl_identifier_test.cc",
     "src/writer/hlsl/generator_impl_return_test.cc",

src/CMakeLists.txt

@@ -544,6 +544,7 @@ if (${TINT_BUILD_HLSL_WRITER})
   list(APPEND TINT_TEST_SRCS
     writer/hlsl/generator_impl_binary_test.cc
     writer/hlsl/generator_impl_break_test.cc
+    writer/hlsl/generator_impl_case_test.cc
     writer/hlsl/generator_impl_continue_test.cc
     writer/hlsl/generator_impl_identifier_test.cc
     writer/hlsl/generator_impl_return_test.cc

src/writer/hlsl/generator_impl.cc

@@ -15,13 +15,29 @@
 #include "src/writer/hlsl/generator_impl.h"
 
 #include "src/ast/binary_expression.h"
+#include "src/ast/bool_literal.h"
+#include "src/ast/case_statement.h"
+#include "src/ast/float_literal.h"
 #include "src/ast/identifier_expression.h"
 #include "src/ast/return_statement.h"
+#include "src/ast/sint_literal.h"
+#include "src/ast/uint_literal.h"
 #include "src/ast/unary_op_expression.h"
 
 namespace tint {
 namespace writer {
 namespace hlsl {
+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(ast::Module* module) : module_(module) {}
 
@@ -145,6 +161,50 @@ 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::EmitContinue(ast::ContinueStatement*) {
   make_indent();
   out_ << "continue;" << std::endl;
@@ -197,6 +257,31 @@ bool GeneratorImpl::EmitIdentifier(ast::IdentifierExpression* expr) {
   return true;
 }
 
+bool GeneratorImpl::EmitLiteral(ast::Literal* lit) {
+  if (lit->IsBool()) {
+    out_ << (lit->AsBool()->IsTrue() ? "true" : "false");
+  } else if (lit->IsFloat()) {
+    auto flags = out_.flags();
+    auto precision = out_.precision();
+
+    out_.flags(flags | std::ios_base::showpoint);
+    out_.precision(std::numeric_limits<float>::max_digits10);
+
+    out_ << lit->AsFloat()->value() << "f";
+
+    out_.precision(precision);
+    out_.flags(flags);
+  } else if (lit->IsSint()) {
+    out_ << lit->AsSint()->value();
+  } else if (lit->IsUint()) {
+    out_ << lit->AsUint()->value() << "u";
+  } else {
+    error_ = "unknown literal type";
+    return false;
+  }
+  return true;
+}
+
 bool GeneratorImpl::EmitReturn(ast::ReturnStatement* stmt) {
   make_indent();
 
@@ -224,6 +309,11 @@ 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->IsReturn()) {
     return EmitReturn(stmt->AsReturn());
   }

src/writer/hlsl/generator_impl.h

@@ -15,6 +15,7 @@
 #ifndef SRC_WRITER_HLSL_GENERATOR_IMPL_H_
 #define SRC_WRITER_HLSL_GENERATOR_IMPL_H_
 
+#include "src/ast/literal.h"
 #include "src/ast/module.h"
 #include "src/scope_stack.h"
 #include "src/writer/hlsl/namer.h"
@@ -43,6 +44,10 @@ 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 a continue statement
   /// @param stmt the statement to emit
   /// @returns true if the statement was emitted successfully
@@ -51,6 +56,10 @@ class GeneratorImpl : public TextGenerator {
   /// @param expr the expression
   /// @returns true if the expression was emitted
   bool EmitExpression(ast::Expression* expr);
+  /// Handles a literal
+  /// @param lit the literal to emit
+  /// @returns true if the literal was successfully emitted
+  bool EmitLiteral(ast::Literal* lit);
   /// Handles generating an identifier expression
   /// @param expr the identifier expression
   /// @returns true if the identifeir was emitted

src/writer/hlsl/generator_impl_case_test.cc

@@ -0,0 +1,141 @@
+// 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/module.h"
+#include "src/ast/sint_literal.h"
+#include "src/ast/type/i32_type.h"
+#include "src/writer/hlsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace hlsl {
+namespace {
+
+using HlslGeneratorImplTest = testing::Test;
+
+TEST_F(HlslGeneratorImplTest, 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));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5: {
+    break;
+  }
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, 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));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5: {
+    break;
+  }
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, 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));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5: {
+    /* fallthrough */
+  }
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, 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));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  case 5:
+  case 6: {
+    break;
+  }
+)");
+}
+
+TEST_F(HlslGeneratorImplTest, Emit_Case_Default) {
+  ast::CaseStatement c;
+
+  ast::StatementList body;
+  body.push_back(std::make_unique<ast::BreakStatement>());
+
+  c.set_body(std::move(body));
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitCase(&c)) << g.error();
+  EXPECT_EQ(g.result(), R"(  default: {
+    break;
+  }
+)");
+}
+
+}  // namespace
+}  // namespace hlsl
+}  // namespace writer
+}  // namespace tint