fix(cuda_std): pack warp shuffle/match return into i64 for LLVM 19 verifier - #391
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LLVM 19's verifier rejects the `align N` return-attribute that rustc's
C ABI lowering attaches to calls returning small aggregates like
{ i32, i8 } (align is only valid on pointer returns). Three intrinsic
wrappers in libintrinsics.ll triggered this:
- __nvvm_warp_shuffle
- __nvvm_warp_match_all_32
- __nvvm_warp_match_all_64
Switch their return type from { i32, i8 } to a packed i64 (low 32 bits
= value, bit 32 = predicate). Primitive integer return ⇒ no struct ABI
⇒ no spurious return-attribute. Uses only LLVM 1.0-era IR primitives
(zext/shl/or), so it's safe under both LLVM 7 (CUDA 12.x libnvvm) and
LLVM 19 (CUDA 13.x libnvvm). Removes the now-redundant
WarpShuffleResult struct.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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August 14, 2026 11:52
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@LegNeato if we could land this one please, thank you very much |
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if we land #386 this becomes smaller, opening it for now
fixes