[PATCH] D86576: [IR] Add NoUndef attribute to Intrinsics.td

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


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Comment at: llvm/include/llvm/IR/Intrinsics.td:1357
+                                 [IntrArgMemOnly, IntrWillReturn,
+                                  NoUndef<ArgIndex<1>>, ImmArg<ArgIndex<2>>]>;
 
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aqjune wrote:
> efriedma wrote:
> > Do masked load/store/gather/scatter have the same problem as memcpy/memmove?  In particular, it seems a bit weird that a masked store with an all-false mask has undefined behavior if the pointer argument is undef.
> In case of masked store/load, I followed Memory sanitizer's behavior.
> MemorySanitizerVisitor's handleMaskedStore and handleMaskedLoad calls insertShadowCheck for the pointer, which checks whether the pointer is undefined IIUC.
> The same thing happens for normal load/stores, but not for memcpy/memset.
I suspect msan's behavior isn't what we want; a completely masked load/store is sort of an edge case, though.

I'm more concerned about gather/scatter; it's much more likely we'll end up with undef vector lanes there.


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  https://reviews.llvm.org/D86576/new/

https://reviews.llvm.org/D86576