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// Copyright 2020 The Dawn & Tint Authors
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#ifndef SRC_TINT_LANG_WGSL_AST_TRANSFORM_FIRST_INDEX_OFFSET_H_
#define SRC_TINT_LANG_WGSL_AST_TRANSFORM_FIRST_INDEX_OFFSET_H_
#include "src/tint/lang/wgsl/ast/transform/transform.h"
namespace tint::ast::transform {
/// Adds firstVertex/Instance (injected via root constants) to
/// vertex/instance index builtins.
///
/// This transform assumes that Name transform has been run before.
///
/// Unlike other APIs, D3D always starts vertex and instance numbering at 0,
/// regardless of the firstVertex/Instance value specified. This transformer
/// adds the value of firstVertex/Instance to each builtin. This action is
/// performed by adding a new constant equal to original builtin +
/// firstVertex/Instance to each function that references one of these builtins.
///
/// Note that D3D does not have any semantics for firstVertex/Instance.
/// Therefore, these values must by passed to the shader.
///
/// Before:
/// ```
/// @builtin(vertex_index) var<in> vert_idx : u32;
/// fn func() -> u32 {
/// return vert_idx;
/// }
/// ```
///
/// After:
/// ```
/// struct TintFirstIndexOffsetData {
/// tint_first_vertex_index : u32;
/// tint_first_instance_index : u32;
/// };
/// @builtin(vertex_index) var<in> tint_first_index_offset_vert_idx : u32;
/// @binding(N) @group(M) var<uniform> tint_first_index_data :
/// TintFirstIndexOffsetData;
/// fn func() -> u32 {
/// const vert_idx = (tint_first_index_offset_vert_idx +
/// tint_first_index_data.tint_first_vertex_index);
/// return vert_idx;
/// }
/// ```
///
class FirstIndexOffset final : public Castable<FirstIndexOffset, Transform> {
public:
/// BindingPoint is consumed by the FirstIndexOffset transform.
/// BindingPoint specifies the binding point of the first index uniform
/// buffer.
struct BindingPoint final : public Castable<BindingPoint, Data> {
/// Constructor
BindingPoint();
/// Constructor
/// @param b the binding index
/// @param g the binding group
BindingPoint(uint32_t b, uint32_t g);
/// Destructor
~BindingPoint() override;
/// `@binding()` for the first vertex / first instance uniform buffer
uint32_t binding = 0;
/// `@group()` for the first vertex / first instance uniform buffer
uint32_t group = 0;
};
/// Data is outputted by the FirstIndexOffset transform.
/// Data holds information about shader usage and constant buffer offsets.
struct Data final : public Castable<Data, transform::Data> {
/// Constructor
/// @param has_vtx_index True if the shader uses vertex_index
/// @param has_inst_index True if the shader uses instance_index
Data(bool has_vtx_index, bool has_inst_index);
/// Copy constructor
Data(const Data&);
/// Destructor
~Data() override;
/// True if the shader uses vertex_index
const bool has_vertex_index;
/// True if the shader uses instance_index
const bool has_instance_index;
};
/// Constructor
FirstIndexOffset();
/// Destructor
~FirstIndexOffset() override;
/// @copydoc Transform::Apply
ApplyResult Apply(const Program& program,
const DataMap& inputs,
DataMap& outputs) const override;
private:
uint32_t binding_ = 0;
uint32_t group_ = 0;
};
} // namespace tint::ast::transform
#endif // SRC_TINT_LANG_WGSL_AST_TRANSFORM_FIRST_INDEX_OFFSET_H_