third_party/rust/wgpu-core/src/timestamp_normalization

Name	Description	Size
common.wgsl		4191
mod.rs	Utility for normalizing GPU timestamp queries to have a consistent 1GHz period. This uses a compute shader to do the normalization, so the timestamps exist in their correct format on the GPU, as is required by the WebGPU specification. ## Algorithm The fundamental operation is multiplying a u64 timestamp by an f32 value. We have neither f64s nor u64s in shaders, so we need to do something more complicated. We first decompose the f32 into a u32 fraction where the denominator is a power of two. We do the computation with f64 for ease of computation, as those can store u32s losslessly. Because the denominator is a power of two, this means the shader can evaluate this divide by using a shift. Additionally, we always choose the largest denominator we can, so that the fraction is as precise as possible. To evaluate this function, we have two helper operations (both in common.wgsl). 1. `u64_mul_u32` multiplies a u64 by a u32 and returns a u96. 2. `shift_right_u96` shifts a u96 right by a given amount, returning a u96. See their implementations for more details. We then multiply the timestamp by the numerator, and shift it right by the denominator. This gives us the normalized timestamp.	15713
timestamp_normalization.wgsl		1227