src/tint/lang/glsl/writer/ast_raise/combine_samplers.h

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#ifndef SRC_TINT_LANG_GLSL_WRITER_AST_RAISE_COMBINE_SAMPLERS_H_
#define SRC_TINT_LANG_GLSL_WRITER_AST_RAISE_COMBINE_SAMPLERS_H_

#include <string>
#include <unordered_map>

#include "src/tint/lang/wgsl/ast/transform/transform.h"

namespace tint::glsl::writer {

/// 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, ast::transform::Transform> {
  public:
    /// Constructor
    CombineSamplers();

    /// Destructor
    ~CombineSamplers() override;

    /// @copydoc ast::transform::Transform::Apply
    ApplyResult Apply(const Program& program,
                      const ast::transform::DataMap& inputs,
                      ast::transform::DataMap& outputs) const override;

  private:
    struct State;
};

}  // namespace tint::glsl::writer

#endif  // SRC_TINT_LANG_GLSL_WRITER_AST_RAISE_COMBINE_SAMPLERS_H_