ast: Add InterpolateDecoration and related enums

Bug: tint:746
Change-Id: Ifd0de8b0e4400a153e67a8e301a7d0523e75898a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56240
Auto-Submit: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/BUILD.gn

@@ -368,6 +368,8 @@ libtint_source_set("libtint_core_all_src") {
     "ast/int_literal.h",
     "ast/internal_decoration.cc",
     "ast/internal_decoration.h",
+    "ast/interpolate_decoration.cc",
+    "ast/interpolate_decoration.h",
     "ast/literal.cc",
     "ast/literal.h",
     "ast/location_decoration.cc",

src/CMakeLists.txt

@@ -112,6 +112,8 @@ set(TINT_LIB_SRCS
   ast/int_literal.h
   ast/internal_decoration.cc
   ast/internal_decoration.h
+  ast/interpolate_decoration.cc
+  ast/interpolate_decoration.h
   ast/literal.cc
   ast/literal.h
   ast/location_decoration.cc
@@ -554,6 +556,7 @@ if(${TINT_BUILD_TESTS})
     ast/identifier_expression_test.cc
     ast/if_statement_test.cc
     ast/int_literal_test.cc
+    ast/interpolate_decoration_test.cc
     ast/intrinsic_texture_helper_test.cc
     ast/intrinsic_texture_helper_test.h
     ast/location_decoration_test.cc

src/ast/interpolate_decoration.cc

@@ -0,0 +1,93 @@
+// 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/interpolate_decoration.h"
+
+#include <string>
+
+#include "src/program_builder.h"
+
+TINT_INSTANTIATE_TYPEINFO(tint::ast::InterpolateDecoration);
+
+namespace tint {
+namespace ast {
+
+InterpolateDecoration::InterpolateDecoration(ProgramID program_id,
+                                             const Source& source,
+                                             InterpolationType type,
+                                             InterpolationSampling sampling)
+    : Base(program_id, source), type_(type), sampling_(sampling) {}
+
+InterpolateDecoration::~InterpolateDecoration() = default;
+
+std::string InterpolateDecoration::name() const {
+  return "interpolate";
+}
+
+void InterpolateDecoration::to_str(const sem::Info&,
+                                   std::ostream& out,
+                                   size_t indent) const {
+  make_indent(out, indent);
+  out << "InterpolateDecoration{" << type_ << " " << sampling_ << "}"
+      << std::endl;
+}
+
+InterpolateDecoration* InterpolateDecoration::Clone(CloneContext* ctx) const {
+  // Clone arguments outside of create() call to have deterministic ordering
+  auto src = ctx->Clone(source());
+  return ctx->dst->create<InterpolateDecoration>(src, type_, sampling_);
+}
+
+std::ostream& operator<<(std::ostream& out, InterpolationType type) {
+  switch (type) {
+    case InterpolationType::kPerspective: {
+      out << "perspective";
+      break;
+    }
+    case InterpolationType::kLinear: {
+      out << "linear";
+      break;
+    }
+    case InterpolationType::kFlat: {
+      out << "flat";
+      break;
+    }
+  }
+  return out;
+}
+
+std::ostream& operator<<(std::ostream& out, InterpolationSampling sampling) {
+  switch (sampling) {
+    case InterpolationSampling::kNone: {
+      out << "none";
+      break;
+    }
+    case InterpolationSampling::kCenter: {
+      out << "center";
+      break;
+    }
+    case InterpolationSampling::kCentroid: {
+      out << "centroid";
+      break;
+    }
+    case InterpolationSampling::kSample: {
+      out << "sample";
+      break;
+    }
+  }
+  return out;
+}
+
+}  // namespace ast
+}  // namespace tint

src/ast/interpolate_decoration.h

@@ -0,0 +1,88 @@
+// 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_INTERPOLATE_DECORATION_H_
+#define SRC_AST_INTERPOLATE_DECORATION_H_
+
+#include <ostream>
+#include <string>
+
+#include "src/ast/decoration.h"
+
+namespace tint {
+namespace ast {
+
+/// The interpolation type.
+enum class InterpolationType { kPerspective, kLinear, kFlat };
+
+/// The interpolation sampling.
+enum class InterpolationSampling { kNone = -1, kCenter, kCentroid, kSample };
+
+/// An interpolate decoration
+class InterpolateDecoration
+    : public Castable<InterpolateDecoration, Decoration> {
+ public:
+  /// Create an interpolate decoration.
+  /// @param program_id the identifier of the program that owns this node
+  /// @param source the source of this decoration
+  /// @param type the interpolation type
+  /// @param sampling the interpolation sampling
+  InterpolateDecoration(ProgramID program_id,
+                        const Source& source,
+                        InterpolationType type,
+                        InterpolationSampling sampling);
+  ~InterpolateDecoration() override;
+
+  /// @returns the interpolation type
+  InterpolationType type() const { return type_; }
+
+  /// @returns the interpolation sampling
+  InterpolationSampling sampling() const { return sampling_; }
+
+  /// @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
+  InterpolateDecoration* Clone(CloneContext* ctx) const override;
+
+ private:
+  InterpolationType const type_;
+  InterpolationSampling const sampling_;
+};
+
+/// @param out the std::ostream to write to
+/// @param type the interpolation type
+/// @return the std::ostream so calls can be chained
+std::ostream& operator<<(std::ostream& out, InterpolationType type);
+
+/// @param out the std::ostream to write to
+/// @param sampling the interpolation sampling
+/// @return the std::ostream so calls can be chained
+std::ostream& operator<<(std::ostream& out, InterpolationSampling sampling);
+
+}  // namespace ast
+}  // namespace tint
+
+#endif  // SRC_AST_INTERPOLATE_DECORATION_H_

src/ast/interpolate_decoration_test.cc

@@ -0,0 +1,41 @@
+// 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/interpolate_decoration.h"
+
+#include "src/ast/test_helper.h"
+
+namespace tint {
+namespace ast {
+namespace {
+
+using InterpolateDecorationTest = TestHelper;
+
+TEST_F(InterpolateDecorationTest, Creation) {
+  auto* d = create<InterpolateDecoration>(InterpolationType::kLinear,
+                                          InterpolationSampling::kCenter);
+  EXPECT_EQ(InterpolationType::kLinear, d->type());
+  EXPECT_EQ(InterpolationSampling::kCenter, d->sampling());
+}
+
+TEST_F(InterpolateDecorationTest, ToStr) {
+  auto* d = create<InterpolateDecoration>(InterpolationType::kPerspective,
+                                          InterpolationSampling::kSample);
+  EXPECT_EQ(str(d), R"(InterpolateDecoration{perspective sample}
+)");
+}
+
+}  // namespace
+}  // namespace ast
+}  // namespace tint

test/BUILD.gn

@@ -175,6 +175,7 @@ tint_unittests_source_set("tint_unittests_core_src") {
     "../src/ast/identifier_expression_test.cc",
     "../src/ast/if_statement_test.cc",
     "../src/ast/int_literal_test.cc",
+    "../src/ast/interpolate_decoration_test.cc",
     "../src/ast/intrinsic_texture_helper_test.cc",
     "../src/ast/intrinsic_texture_helper_test.h",
     "../src/ast/location_decoration_test.cc",