[InstCombine] Infer nuw flags for C-(X+C2)
-> (C-C2)-X
#72373
Merged
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This patch improves https://reviews.llvm.org/D152068 by inferring NUW flags for sub insts.
It is worth noting that we don't need to check overflow for
C-C2
.Alive2: https://alive2.llvm.org/ce/z/uutGpS
This missed optimization is discovered with the help of AliveToolkit/alive2#962.