[PATCH] D144903: [X86] Drop single use check for freeze(undef) in LowerAVXCONCAT_VECTORS

Fri Mar 10 11:14:47 PST 2023

nlopes added a comment.

In D144903#4182498 <https://reviews.llvm.org/D144903#4182498>, @efriedma wrote:

> I think the point of the hasOneUse check is to avoid a possible miscompile; if a FREEZE has more than one use, all users need to see the same value.  So not sure dropping the check is correct in general.

Good point.
This patch is not correct, must be reverted.
The shufflevectors create copies of a same 'freeze poison'. These copies must see the same value, and that's not the case after this patch.

Repository:
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  https://reviews.llvm.org/D144903/new/

https://reviews.llvm.org/D144903