dawn-cmake/src/transform/first_index_offset.h

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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_TRANSFORM_FIRST_INDEX_OFFSET_H_
#define SRC_TRANSFORM_FIRST_INDEX_OFFSET_H_
#include <string>
#include "src/ast/variable_decl_statement.h"
#include "src/transform/transform.h"
namespace tint {
namespace 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:
/// [[block]]
/// 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 : public Transform {
public:
/// Data is outputted by the FirstIndexOffset transform.
/// Data holds information about shader usage and constant buffer offsets.
struct Data : 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
/// @param first_vtx_offset Offset of first vertex into constant buffer
/// @param first_inst_offset Offset of first instance into constant buffer
Data(bool has_vtx_index,
bool has_inst_index,
uint32_t first_vtx_offset,
uint32_t first_inst_offset);
/// Copy constructor
Data(const Data&);
/// Destructor
~Data() override;
/// True if the shader uses vertex_index
bool const has_vertex_index;
/// True if the shader uses instance_index
bool const has_instance_index;
/// Offset of first vertex into constant buffer
uint32_t const first_vertex_offset;
/// Offset of first instance into constant buffer
uint32_t const first_instance_offset;
};
/// Constructor
/// @param binding the binding() for firstVertex/Instance uniform
/// @param group the group() for firstVertex/Instance uniform
FirstIndexOffset(uint32_t binding, uint32_t group);
~FirstIndexOffset() override;
/// Runs the transform on `program`, returning the transformation result.
/// @param program the source program to transform
/// @param data optional extra transform-specific input data
/// @returns the transformation result
Output Run(const Program* program, const DataMap& data = {}) override;
private:
struct State {
/// Adds uniform buffer with firstVertex/Instance to the program builder
/// @returns variable of new uniform buffer
ast::Variable* AddUniformBuffer();
/// Adds constant with modified original_name builtin to func
/// @param original_name the name of the original builtin used in function
/// @param field_name name of field in firstVertex/Instance buffer
/// @param buffer_var variable of firstVertex/Instance buffer
ast::VariableDeclStatement* CreateFirstIndexOffset(
const std::string& original_name,
const std::string& field_name,
ast::Variable* buffer_var);
ProgramBuilder* const dst;
uint32_t const binding;
uint32_t const group;
bool has_vertex_index = false;
bool has_instance_index = false;
uint32_t vertex_index_offset = 0;
uint32_t instance_index_offset = 0;
};
uint32_t binding_;
uint32_t group_;
};
} // namespace transform
} // namespace tint
#endif // SRC_TRANSFORM_FIRST_INDEX_OFFSET_H_