[PATCH] D142115: [ValueTracking] Take poison-generating metadata into account (PR59888)

[Nuno Lopes via Phabricator via llvm-commits]

nlopes accepted this revision.
nlopes added inline comments.
This revision is now accepted and ready to land.


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Comment at: llvm/lib/IR/Instruction.cpp:217
+         hasMetadata(LLVMContext::MD_nonnull) ||
+         hasMetadata(LLVMContext::MD_align);
+}
----------------
nikic wrote:
> nlopes wrote:
> > not sure about align.
> > If a pointer is not sufficiently aligned, a load may crash. Returning poison in that case is not strong enough for the hardware behavior.
> This is the same semantics we use for the param attribute. I think it's okay because any kind of speculation requires dereferenceable and align, and dereferenceable implies noundef.
> 
> (Note that this is the align metadata that specifies the alignment of the returned pointer, not the alignment of the load itself.)
Oh, I see.
I didn't have that implemented in Alive. Just added support.


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https://reviews.llvm.org/D142115