ast: Add InvariantDecoration

Bug: tint:772
Change-Id: Icd1892a1affed10af8e7b90257129fa54360815e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/57640
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Ben Clayton <bclayton@google.com>

src/BUILD.gn

@@ -372,6 +372,8 @@ libtint_source_set("libtint_core_all_src") {
     "ast/internal_decoration.h",
     "ast/interpolate_decoration.cc",
     "ast/interpolate_decoration.h",
+    "ast/invariant_decoration.cc",
+    "ast/invariant_decoration.h",
     "ast/literal.cc",
     "ast/literal.h",
     "ast/location_decoration.cc",

src/CMakeLists.txt

@@ -116,6 +116,8 @@ set(TINT_LIB_SRCS
   ast/internal_decoration.h
   ast/interpolate_decoration.cc
   ast/interpolate_decoration.h
+  ast/invariant_decoration.cc
+  ast/invariant_decoration.h
   ast/literal.cc
   ast/literal.h
   ast/location_decoration.cc
@@ -568,6 +570,7 @@ if(${TINT_BUILD_TESTS})
     ast/interpolate_decoration_test.cc
     ast/intrinsic_texture_helper_test.cc
     ast/intrinsic_texture_helper_test.h
+    ast/invariant_decoration_test.cc
     ast/location_decoration_test.cc
     ast/loop_statement_test.cc
     ast/matrix_test.cc

src/ast/invariant_decoration.cc

@@ -0,0 +1,48 @@
+// Copyright 2021 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 "src/ast/invariant_decoration.h"
+
+#include "src/program_builder.h"
+
+TINT_INSTANTIATE_TYPEINFO(tint::ast::InvariantDecoration);
+
+namespace tint {
+namespace ast {
+
+InvariantDecoration::InvariantDecoration(ProgramID program_id,
+                                         const Source& source)
+    : Base(program_id, source) {}
+
+InvariantDecoration::~InvariantDecoration() = default;
+
+std::string InvariantDecoration::name() const {
+  return "invariant";
+}
+
+void InvariantDecoration::to_str(const sem::Info&,
+                                 std::ostream& out,
+                                 size_t indent) const {
+  make_indent(out, indent);
+  out << "InvariantDecoration";
+}
+
+InvariantDecoration* InvariantDecoration::Clone(CloneContext* ctx) const {
+  // Clone arguments outside of create() call to have deterministic ordering
+  auto src = ctx->Clone(source());
+  return ctx->dst->create<InvariantDecoration>(src);
+}
+
+}  // namespace ast
+}  // namespace tint

src/ast/invariant_decoration.h

@@ -0,0 +1,55 @@
+// Copyright 2021 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.
+
+#ifndef SRC_AST_INVARIANT_DECORATION_H_
+#define SRC_AST_INVARIANT_DECORATION_H_
+
+#include <string>
+
+#include "src/ast/decoration.h"
+
+namespace tint {
+namespace ast {
+
+/// The invariant attribute
+class InvariantDecoration : public Castable<InvariantDecoration, Decoration> {
+ public:
+  /// constructor
+  /// @param program_id the identifier of the program that owns this node
+  /// @param source the source of this decoration
+  InvariantDecoration(ProgramID program_id, const Source& source);
+  ~InvariantDecoration() override;
+
+  /// @returns the WGSL name for the decoration
+  std::string name() const override;
+
+  /// Outputs the decoration to the given stream
+  /// @param sem the semantic info for the program
+  /// @param out the stream to write to
+  /// @param indent number of spaces to indent the node when writing
+  void to_str(const sem::Info& sem,
+              std::ostream& out,
+              size_t indent) const override;
+
+  /// Clones this node and all transitive child nodes using the `CloneContext`
+  /// `ctx`.
+  /// @param ctx the clone context
+  /// @return the newly cloned node
+  InvariantDecoration* Clone(CloneContext* ctx) const override;
+};
+
+}  // namespace ast
+}  // namespace tint
+
+#endif  // SRC_AST_INVARIANT_DECORATION_H_

src/ast/invariant_decoration_test.cc

@@ -0,0 +1,32 @@
+// Copyright 2021 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 "src/ast/invariant_decoration.h"
+
+#include "src/ast/test_helper.h"
+
+namespace tint {
+namespace ast {
+namespace {
+
+using InvariantDecorationTest = TestHelper;
+
+TEST_F(InvariantDecorationTest, ToStr) {
+  auto* d = create<InvariantDecoration>();
+  EXPECT_EQ(str(d), "InvariantDecoration");
+}
+
+}  // namespace
+}  // namespace ast
+}  // namespace tint

test/BUILD.gn

@@ -179,6 +179,7 @@ tint_unittests_source_set("tint_unittests_core_src") {
     "../src/ast/interpolate_decoration_test.cc",
     "../src/ast/intrinsic_texture_helper_test.cc",
     "../src/ast/intrinsic_texture_helper_test.h",
+    "../src/ast/invariant_decoration_test.cc",
     "../src/ast/location_decoration_test.cc",
     "../src/ast/loop_statement_test.cc",
     "../src/ast/matrix_test.cc",