// Copyright 2024 The Dawn & Tint Authors // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are met: // // 1. Redistributions of source code must retain the above copyright notice, this // list of conditions and the following disclaimer. // // 2. Redistributions in binary form must reproduce the above copyright notice, // this list of conditions and the following disclaimer in the documentation // and/or other materials provided with the distribution. // // 3. Neither the name of the copyright holder nor the names of its // contributors may be used to endorse or promote products derived from // this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. #ifndef SRC_TINT_LANG_WGSL_AST_TRANSFORM_OFFSET_FIRST_INDEX_H_ #define SRC_TINT_LANG_WGSL_AST_TRANSFORM_OFFSET_FIRST_INDEX_H_ #include "src/tint/lang/wgsl/ast/transform/transform.h" #include "src/tint/utils/reflection/reflection.h" namespace tint::ast::transform { /// Adds firstVertex/Instance (injected via push constants) to /// vertex/instance index builtins. /// /// This transform assumes that the Name and AddBlockAttribute transforms have been run before. /// /// Some shading languages start vertex and instance numbering at 0, /// regardless of the firstVertex/firstInstance value specified. This transform /// adds the value of firstVertex/firstInstance to each builtin. This action is /// performed by adding a new push constant equal to original builtin + /// firstVertex/firstInstance to each function that references one of /// these builtins. /// /// For D3D, this affects both firstVertex and firstInstance. For OpenGL, /// it applies to only firstInstance. For this reason, the first_vertex_offset /// and first_instance_offset are optional, where std::nullopt indicates that /// no substitution is to be performed. /// /// Before: /// ``` /// @builtin(vertex_index) var<in> vert_idx : u32; /// @builtin(instance_index) var<in> inst_idx : u32; /// fn func() -> u32 { /// return vert_idx * inst_idx; /// } /// ``` /// /// After: /// ``` /// struct PushConstants { /// first_vertex : u32, /// first_instance : u32, /// } /// /// var<push_constant> push_constants : PushConstants; /// /// @builtin(vertex_index) var<in> vert_idx : u32; /// @builtin(instance_index) var<in> inst_idx : u32; /// fn func() -> u32 { /// return (vert_idx + push_constants.first_vertex) * (inst_idx + /// push_constants.first_instance); /// } /// ``` /// class OffsetFirstIndex final : public Castable<OffsetFirstIndex, Transform> { … }; } // namespace tint::ast::transform #endif // SRC_TINT_LANG_WGSL_AST_TRANSFORM_OFFSET_FIRST_INDEX_H_