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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
// 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 "src/ast/module.h"
#include "src/ast/variable_decl_statement.h"
#include "src/symbol.h"
#include "src/transform/transform.h"
namespace tint {
namespace transform {
/// Adds firstVertex/Instance (injected via root constants) to
/// vertex/instance_idx 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 {
/// [[offset(0)]] tint_first_vertex_index : u32;
/// [[offset(4)]] 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 {
/// 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 `module`, returning the transformation result.
/// @note Users of Tint should register the transform with transform manager
/// and invoke its Run(), instead of directly calling the transform's Run().
/// Calling Run() directly does not perform module state cleanup operations.
/// @param module the source module to transform
/// @returns the transformation result
Output Run(ast::Module* module) override;
/// @returns whether shader uses vertex_index
bool HasVertexIndex();
/// @returns whether shader uses instance_index
bool HasInstanceIndex();
/// @returns offset of firstVertex into constant buffer
uint32_t GetFirstVertexOffset();
/// @returns offset of firstInstance into constant buffer
uint32_t GetFirstInstanceOffset();
/// Adds uniform buffer with firstVertex/Instance to module
/// @returns variable of new uniform buffer
ast::Variable* AddUniformBuffer(ast::Module* mod);
/// 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
/// @param module the target module to contain the new ast nodes
ast::VariableDeclStatement* CreateFirstIndexOffset(
const std::string& original_name,
const std::string& field_name,
ast::Variable* buffer_var,
ast::Module* module);
uint32_t binding_;
uint32_t group_;
bool has_vertex_index_ = false;
bool has_instance_index_ = false;
uint32_t vertex_index_offset_ = 0;
uint32_t instance_index_offset_ = 0;
} // namespace transform
} // namespace tint