Add reset method to the generators.

This CL allows the backend generators to be reset so they can be re-run
again.

Bug: tint:211
Change-Id: I67b0c650d0ab4615130777becc513099247339c9
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/28043
Commit-Queue: David Neto <dneto@google.com>
Reviewed-by: David Neto <dneto@google.com>

src/writer/hlsl/generator.cc

@@ -26,6 +26,12 @@ Generator::Generator(ast::Module module)
 
 Generator::~Generator() = default;
 
+void Generator::Reset() {
+  set_error("");
+  out_ = std::ostringstream();
+  impl_ = std::make_unique<GeneratorImpl>(&module_);
+}
+
 bool Generator::Generate() {
   auto ret = impl_->Generate(out_);
   if (!ret) {

src/writer/hlsl/generator.h

@@ -34,6 +34,9 @@ class Generator : public Text {
   explicit Generator(ast::Module module);
   ~Generator() override;
 
+  /// Resets the generator
+  void Reset() override;
+
   /// Generates the result data
   /// @returns true on successful generation; false otherwise
   bool Generate() override;

src/writer/hlsl/generator_impl.h

@@ -52,6 +52,9 @@ class GeneratorImpl {
   /// @returns the error
   std::string error() const { return error_; }
 
+  /// Resets the generator
+  void Reset();
+
   /// @param out the output stream
   /// @returns true on successful generation; false otherwise
   bool Generate(std::ostream& out);

src/writer/msl/generator.cc

@@ -26,6 +26,11 @@ Generator::Generator(ast::Module module)
 
 Generator::~Generator() = default;
 
+void Generator::Reset() {
+  set_error("");
+  impl_ = std::make_unique<GeneratorImpl>(&module_);
+}
+
 bool Generator::Generate() {
   auto ret = impl_->Generate();
   if (!ret) {

src/writer/msl/generator.h

@@ -33,6 +33,9 @@ class Generator : public Text {
   explicit Generator(ast::Module module);
   ~Generator() override;
 
+  /// Resets the generator
+  void Reset() override;
+
   /// Generates the result data
   /// @returns true on successful generation; false otherwise
   bool Generate() override;

src/writer/spirv/generator.cc

@@ -27,6 +27,11 @@ Generator::Generator(ast::Module module)
 
 Generator::~Generator() = default;
 
+void Generator::Reset() {
+  builder_ = std::make_unique<Builder>(&module_);
+  writer_ = std::make_unique<BinaryWriter>();
+}
+
 bool Generator::Generate() {
   if (!builder_->Build()) {
     set_error(builder_->error());

src/writer/spirv/generator.h

@@ -35,6 +35,9 @@ class Generator : public writer::Writer {
   explicit Generator(ast::Module module);
   ~Generator() override;
 
+  /// Resets the generator
+  void Reset() override;
+
   /// Generates the result data
   /// @returns true on successful generation; false otherwise
   bool Generate() override;

src/writer/wgsl/generator.cc

@@ -25,6 +25,11 @@ Generator::Generator(ast::Module module)
 
 Generator::~Generator() = default;
 
+void Generator::Reset() {
+  set_error("");
+  impl_ = std::make_unique<GeneratorImpl>();
+}
+
 bool Generator::Generate() {
   auto ret = impl_->Generate(module_);
   if (!ret) {

src/writer/wgsl/generator.h

@@ -33,6 +33,9 @@ class Generator : public Text {
   explicit Generator(ast::Module module);
   ~Generator() override;
 
+  /// Resets the generator
+  void Reset() override;
+
   /// Generates the result data
   /// @returns true on successful generation; false otherwise
   bool Generate() override;

src/writer/writer.h

@@ -30,6 +30,9 @@ class Writer {
   /// @returns the writer error string
   const std::string& error() const { return error_; }
 
+  /// Resets the generator
+  virtual void Reset() = 0;
+
   /// Converts the module into the desired format
   /// @returns true on success; false on failure
   virtual bool Generate() = 0;