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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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#include <string>
#include <unordered_map>
#include "src/tint/sem/sampler_texture_pair.h"
#include "src/tint/transform/transform.h"
namespace tint::transform {
/// This transform converts all separate texture/sampler refences in a
/// program into combined texture/samplers. This is required for GLSL,
/// which does not support separate texture/samplers.
/// It utilizes the texture/sampler information collected by the
/// Resolver and stored on each sem::Function. For each function, all
/// separate texture/sampler parameters in the function signature are
/// removed. For each unique pair, if both texture and sampler are
/// global variables, the function passes the corresponding combined
/// global stored in global_combined_texture_samplers_ at the call
/// site. Otherwise, either the texture or sampler must be a function
/// parameter. In this case, a new parameter is added to the function
/// signature. All separate texture/sampler parameters are removed.
/// All texture builtin callsites are modified to pass the combined
/// texture/sampler as the first argument, and separate texture/sampler
/// arguments are removed.
/// Note that the sampler may be null, indicating that only a texture
/// reference was required (e.g., textureLoad). In this case, a
/// placeholder global sampler is used at the AST level. This will be
/// combined with the original texture to give a combined global, and
/// the placeholder removed (ignored) by the GLSL writer.
/// Note that the combined samplers are actually represented by a
/// Texture node at the AST level, since this contains all the
/// information needed to represent a combined sampler in GLSL
/// (dimensionality, component type, etc). The GLSL writer outputs such
/// (Tint) Textures as (GLSL) Samplers.
class CombineSamplers final : public Castable<CombineSamplers, Transform> {
/// A pair of binding points.
using SamplerTexturePair = sem::SamplerTexturePair;
/// A map from a sampler/texture pair to a named global.
using BindingMap = std::unordered_map<SamplerTexturePair, std::string>;
/// The client-provided mapping from separate texture and sampler binding
/// points to combined sampler binding point.
struct BindingInfo final : public Castable<Data, transform::Data> {
/// Constructor
/// @param map the map of all (texture, sampler) -> (combined) pairs
/// @param placeholder the binding point to use for placeholder samplers.
BindingInfo(const BindingMap& map, const sem::BindingPoint& placeholder);
/// Copy constructor
/// @param other the other BindingInfo to copy
BindingInfo(const BindingInfo& other);
/// Destructor
~BindingInfo() override;
/// A map of bindings from (texture, sampler) -> combined sampler.
BindingMap binding_map;
/// The binding point to use for placeholder samplers.
sem::BindingPoint placeholder_binding_point;
/// Constructor
/// Destructor
~CombineSamplers() override;
/// The PIMPL state for this transform
struct State;
/// Runs the transform using the CloneContext built for transforming a
/// program. Run() is responsible for calling Clone() on the CloneContext.
/// @param ctx the CloneContext primed with the input program and
/// ProgramBuilder
/// @param inputs optional extra transform-specific input data
/// @param outputs optional extra transform-specific output data
void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) const override;
} // namespace tint::transform