[PATCH] D116804: [x86] use SETCC_CARRY instead of SBB node for select lowering

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In D116804#3290631 <https://reviews.llvm.org/D116804#3290631>, @craig.topper wrote:

> Won't SETB_C32r be turned into SBB32rr by expandPostRAPseudo before we get to BreakFalseDeps? But I don't think BreakFalseDeps is prepared to deal with a tied dest/src that's also used by another source.

Ah, yes - it does become SBB before we run BreakFalseDeps. I had my breakpoints mixed up and missed that. But a quick hack shows the limitation you're suggesting; we insert the xor to clear the reg between the cmp and the sbb user, so that can't work.


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