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[wasm][JIT] Use TYP_SIMD16 register type for 16-byte struct layouts on Wasm - #134984
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…n Wasm Revert the Wasm exclusion added in #129494 now that Wasm SIMD16 local loads are no longer NYI. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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@adamperlin @AndyAyersMS this looks like a nice win? |
jakobbotsch
approved these changes
Oct 1, 2026
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Motivation
a17debe (#129494) excluded Wasm from the 16-byte
TYP_SIMD16case inClassLayout::GetRegisterType()while Wasm SIMD16 local loads were still NYI. Those SIMD NYIs are no longer present insrc/coreclr/jit/codegenwasm.cpp.Because of the exclusion, on Wasm a struct wrapping
Vector128<T>that is returned asv128(call typedsimd16) and stored to aTYP_STRUCTlocal haslclRegType == TYP_UNDEF, soLowering::LowerStoreLocCommonroutes it throughSpillStructCallResult: a new do-not-enregister temp, aSTORE_LCL_FLD simd16into it, then a struct copy into the destination. That path also crashed crossgen2 with a nullReturnTypeDescdereference (#134976, fixed separately in #134981). This PR removes the reason Wasm takes that path for v128 returns.Change
In
ClassLayout::GetRegisterType()(src/coreclr/jit/layout.h), change#if defined(FEATURE_SIMD) && !defined(TARGET_WASM)back to#ifdef FEATURE_SIMD, so 16-byte struct layouts getTYP_SIMD16as their register type on Wasm as on other SIMD targets.Validation
Performed in a sibling worktree: browser-wasm Checked, osx-arm64 host crossgen2, with the #134981 fix also applied.
./build.sh -s clr+libs -os browser -c checked -lc release: succeededsrc/tests/build.sh -browser checked priority1 -test:JIT/HardwareIntrinsics/HardwareIntrinsics_General_r.csproj -test:JIT/HardwareIntrinsics/HardwareIntrinsics_General_ro.csproj /p:LibrariesConfiguration=Release: succeededsrc/tests/run.sh wasm checked --runcrossgen2tests --node --runner-filter=HardwareIntrinsics_General(IL-CG2 dirs and .wasm images were deleted first to force recompilation):HardwareIntrinsics_General_r: 2584/2584 passedHardwareIntrinsics_General_ro: 2551/2551 passedVectorImmBinaryOpTest__op_LeftShiftByte1:RunStructLclFldScenario(Vector128_1_r): the JIT no longer creates theReturn value tempspill and stores thesimd16call result directly.Vector128_1_r.wasm: 4,957,655 → 4,951,047 bytes (-6.6 KB)Vector128_1_ro.wasm: 4,926,510 → 4,919,838 bytes (-6.7 KB)On this branch,
./build.sh clr.wasmjit -c checkedsucceeded.Caveat
Validation covered only the HardwareIntrinsics General runners. This change affects every 16-byte struct local on Wasm, so it needs broader Wasm R2R coverage (e.g. the outerloop R2R_CG2 browser-wasm lane) and sign-off from the Wasm JIT owners.
Related to #134976 and #134981
Note
This PR description was drafted with GitHub Copilot assistance.