[PATCH] D57789: [CGP] form usub with overflow from sub+icmp

Fri Feb 8 05:48:04 PST 2019

nemanjai added a comment.

I'll apply this and try it to see what is changed in the test cases. I'll report back when that's done.

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Comment at: test/CodeGen/PowerPC/bdzlr.ll:57
 ; CHECK: bnelr
-; CHECK: bdzlr
+; CHECK: bnelr
 ; CHECK-NOT: blr
----------------
I have to look at the entire codegen here a little more closely. The reason I think this requires deeper investigation is that it is changing a branch from the CTR-decrementing `bdzlr` to the `bnelr` that doesn't touch the CTR. So I want to make sure we are not preventing the formation of CTR loops by this change.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57789/new/

https://reviews.llvm.org/D57789