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// Copyright 2022 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_TINT_TRANSFORM_TRUNCATE_INTERSTAGE_VARIABLES_H_
#define SRC_TINT_TRANSFORM_TRUNCATE_INTERSTAGE_VARIABLES_H_
#include <bitset>
#include "src/tint/sem/binding_point.h"
#include "src/tint/transform/transform.h"
namespace tint::transform {
/// TruncateInterstageVariables is a transform that truncate interstage variables.
/// It must be run after CanonicalizeEntryPointIO which guarantees all interstage variables of
/// a given entry point are grouped into one shader IO struct.
/// It replaces `original shader IO struct` with a `new wrapper struct` containing builtin IOs
/// and user-defined IO whose locations are marked in the interstage_locations bitset from the
/// config. The return statements of `original shader IO struct` are wrapped by a mapping function
/// that initializes the members of `new wrapper struct` with values from `original shader IO
/// struct`. IO attributes of members in `original shader IO struct` are removed, other attributes
/// still preserve.
///
/// For example:
///
/// ```
/// struct ShaderIO {
/// @builtin(position) @invariant pos: vec4<f32>,
/// @location(1) f_1: f32,
/// @location(3) @align(16) f_3: f32,
/// @location(5) @interpolate(flat) @align(16) @size(16) f_5: u32,
/// }
/// @vertex
/// fn f() -> ShaderIO {
/// var io: ShaderIO;
/// io.pos = vec4<f32>(1.0, 1.0, 1.0, 1.0);
/// io.f_1 = 1.0;
/// io.f_3 = io.f_1 + 3.0;
/// io.f_5 = 1u;
/// return io;
/// }
/// ```
///
/// With config.interstage_locations[3] and [5] set to true, is transformed to:
///
/// ```
/// struct tint_symbol {
/// @builtin(position) @invariant
/// pos : vec4<f32>,
/// @location(3) @align(16)
/// f_3 : f32,
/// @location(5) @interpolate(flat) @align(16) @size(16)
/// f_5 : u32,
/// }
///
/// fn truncate_shader_output(io : ShaderIO) -> tint_symbol {
/// return tint_symbol(io.pos, io.f_3, io.f_5);
/// }
///
/// struct ShaderIO {
/// pos : vec4<f32>,
/// f_1 : f32,
/// @align(16)
/// f_3 : f32,
/// @align(16) @size(16)
/// f_5 : u32,
/// }
///
/// @vertex
/// fn f() -> tint_symbol {
/// var io : ShaderIO;
/// io.pos = vec4<f32>(1.0, 1.0, 1.0, 1.0);
/// io.f_1 = 1.0;
/// io.f_3 = (io.f_1 + 3.0);
/// io.f_5 = 1u;
/// return truncate_shader_output(io);
/// }
/// ```
///
class TruncateInterstageVariables final : public Castable<TruncateInterstageVariables, Transform> {
public:
/// Configuration options for the transform
struct Config final : public Castable<Config, Data> {
/// Constructor
Config();
/// Copy constructor
Config(const Config&);
/// Destructor
~Config() override;
/// Assignment operator
/// @returns this Config
Config& operator=(const Config&);
/// Indicate which interstage io locations are actually used by the later stage.
/// There can be at most 16 user defined interstage variables with locations.
std::bitset<16> interstage_locations;
/// Reflect the fields of this class so that it can be used by tint::ForeachField()
TINT_REFLECT(interstage_variables);
};
/// Constructor using a the configuration provided in the input Data
TruncateInterstageVariables();
/// Destructor
~TruncateInterstageVariables() override;
/// @copydoc Transform::Apply
ApplyResult Apply(const Program* program,
const DataMap& inputs,
DataMap& outputs) const override;
};
} // namespace tint::transform
#endif // SRC_TINT_TRANSFORM_TRUNCATE_INTERSTAGE_VARIABLES_H_