[PATCH] D63405: GlobalISel: Don't lose fneg flags when lowering to fsub
Cameron McInally via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Jun 17 12:46:01 PDT 2019
cameron.mcinally added a comment.
In D63405#1546701 <https://reviews.llvm.org/D63405#1546701>, @spatel wrote:
> But there's a separate question that is raised here: why is it legal to convert fneg to fsub -0.0? That loosens the IEEE requirement when dealing with a NAN. I'd think this should be legalized by converting to integer and flipping the sign bit (xor).
> ping @cameron.mcinally
Sanjay is correct. It’s not safe to convert fneg->fsub without nnan.
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https://reviews.llvm.org/D63405
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