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// 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.
#ifndef SRC_AST_STRUCT_MEMBER_OFFSET_DECORATION_H_
#define SRC_AST_STRUCT_MEMBER_OFFSET_DECORATION_H_
#include <string>
#include "src/ast/decoration.h"
namespace tint {
namespace ast {
/// A struct member offset decoration
/// @note The WGSL spec removed the `[[offset(n)]]` decoration for `[[size(n)]]`
/// and `[[align(n)]]` in https://github.com/gpuweb/gpuweb/pull/1447. However
/// this decoration is kept because the SPIR-V reader has to deal with absolute
/// offsets, and transforming these to size / align is complex and can be done
/// in a number of ways. The Resolver is responsible for consuming the size and
/// align decorations and transforming these into absolute offsets. It is
/// trivial for the Resolver to handle `[[offset(n)]]` or `[[size(n)]]` /
/// `[[align(n)]]` decorations, so this is what we do, keeping all the layout
/// logic in one place.
class StructMemberOffsetDecoration
: public Castable<StructMemberOffsetDecoration, Decoration> {
public:
/// constructor
/// @param program_id the identifier of the program that owns this node
/// @param source the source of this decoration
/// @param offset the offset value
StructMemberOffsetDecoration(ProgramID program_id,
const Source& source,
uint32_t offset);
~StructMemberOffsetDecoration() override;
/// @returns the offset value
uint32_t offset() const { return offset_; }
/// @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
StructMemberOffsetDecoration* Clone(CloneContext* ctx) const override;
private:
uint32_t const offset_;
};
} // namespace ast
} // namespace tint
#endif // SRC_AST_STRUCT_MEMBER_OFFSET_DECORATION_H_