wasm: do not enable relaxed SIMD by default - #6020
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A module compiled with -mrelaxed-simd fails to instantiate on engines that lack the relaxed-simd feature, including shipping Safari. Keep SIMD128 as the portable default and opt in with WASM_RELAXED_SIMD=1. Signed-off-by: Julien Jerphanion <git@jjerphan.xyz>
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Verified locally with Emscripten 4.0.9 ( Default Kernels compiled both ways (SGEMM/DGEMM, CGEMM/ZGEMM, SDOT/DDOT/DSDOT, SROT, DTRMM_LN), linked with those symbols exported, then
Default SGEMM WAT is |
Encode the portable-default vs WASM_RELAXED_SIMD=1 checks (compile flags, relaxed_madd opcode counts, and SIMD128 instantiate) so they can be re-run after a WASM configure. Signed-off-by: Julien Jerphanion <git@jjerphan.xyz>
Signed-off-by: Julien Jerphanion <git@jjerphan.xyz>
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Summary
Makefile.wasmcurrently passes-mrelaxed-simdon every WASM object, so GEMM/DOT/ROT emitrelaxed_maddinto the final module. WebAssembly validates the whole module: engines that do not implement relaxed SIMD reject instantiate, even if those kernels are never called. Shipping Safari / JavaScriptCore is in that set (feature status).-msimd128) as the default.WASM_RELAXED_SIMD=1(Make) or-DWASM_RELAXED_SIMD=ON(CMake). Kernels already switch on__wasm_relaxed_simd__.docs/install.md.Test plan
After a WASM configure (
ARCH=wasminMakefile.conf), withemccandwasm-disonPATH:That script checks:
-msimd128and not-mrelaxed-simd.relaxed_madd, and Node can instantiate that SIMD128-only module.WASM_RELAXED_SIMD=1passes-mrelaxed-simdand those kernels emitrelaxed_madd.