[PATCH] D23570: Fix SystemZ compilation abort caused by negative AND mask

Ulrich Weigand via llvm-commits llvm-commits at lists.llvm.org
Wed Aug 17 09:13:21 PDT 2016


uweigand added a comment.

In https://reviews.llvm.org/D23570#518162, @colpell wrote:

> This patch truncates the constant to 16 bits, but the actual optimization of using NILL instead of NILF is still covered by the peepholes in SystemZInstrInfo.td. If those peepholes are removed, then we still end up using NILF in cases where we could have used NILL.


Ah, I see.  In this case, I think the best way would be to, instead of truncating the constant, making sure the high bits are *set*, so that instruction selection will then prefer NILL automatically ...


https://reviews.llvm.org/D23570





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