Add WASM SIMD128 path for f_pixel::diff()#129
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kornelski merged 1 commit intoImageOptim:mainfrom Feb 11, 2026
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Add a wasm32+simd128 implementation of the hot diff() function using safe core::arch::wasm32 intrinsics (f32x4 constructor, no unsafe). Translates the existing SSE/NEON pattern: - f32x4() to pack ARGB into a v128 (safe, no pointer load) - f32x4_sub/add/mul/max for packed arithmetic - f32x4_extract_lane + scalar add for horizontal RGB sum Also adds wasm32+simd128 to the repr(C, align(16)) cfg and excludes it from the scalar fallback guard. Measured ~1.9x end-to-end speedup on a 256x256 quantization benchmark running in wasmtime (scalar: 260ms/iter → simd128: 135ms/iter).
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Summary
wasm32 + simd128implementation off_pixel::diff()using safecore::arch::wasm32intrinsicswasm32 + simd128to therepr(C, align(16))cfg onf_pixelwasm32 + simd128from the scalar fallbackcfg(not(...))The implementation uses the safe
f32x4()constructor (nounsafeblock, no raw pointers) and follows the same arithmetic pattern as the existing SSE and NEON paths. No new dependencies — everything is fromcore::arch::wasm32(stable since Rust 1.54).Benchmark
256x256 full quantization pipeline in wasmtime (5 iterations, release mode):
Changes
One file:
src/pal.rs— 27 lines added, 2 lines modified (cfg guards).