[PATCH] D31398: [X86][X86 intrinsics]Folding cmp(sub(a, b), 0) into cmp(a, b) optimization

[Steve Canon via Phabricator via llvm-commits]

scanon added a reviewer: hfinkel.
scanon added a comment.

`(x-y) == 0 --> x == y` does not require nsz (zeros of any sign compare equal), nor does it require nnan (if x or y is NaN, both comparisons are false). It *does* require ninf (because inf-inf = NaN), and it also requires that subnormals are not flushed by the CPU. There's been some churn around flushing recently, Hal may have thoughts (+Hal).


https://reviews.llvm.org/D31398