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

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/IR/Instruction.cpp:217
+         hasMetadata(LLVMContext::MD_nonnull) ||
+         hasMetadata(LLVMContext::MD_align);
+}
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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.)


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  https://reviews.llvm.org/D142115/new/

https://reviews.llvm.org/D142115