[PATCH] D135847: [PowerPC] don't check CTR clobber in hardware loop insertion pass

Sun Nov 13 23:29:00 PST 2022

shchenz added inline comments.

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Comment at: llvm/test/CodeGen/PowerPC/pr55463.ll:71
 ; CHECK-NEXT:    evmergelo 3, 3, 4
-; CHECK-NEXT:    addi 28, 28, 1
+; CHECK-NEXT:    addi 28, 28, -1
 ; CHECK-NEXT:    cmplwi 28, 0
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shchenz wrote:
> lkail wrote:
> > nit: `undef` leads to flag flip.
> Can you be more specific? Do you mean we should not use `addi -1`? The `addi -1` is hard-coded. See https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp#L263-L266 .
The loop count for this loop is `undef`, so ideally this loop can be totally optimized out, I tried to fix this in D137758, but the reviewer suggested this should not be an issue as long as opt is able to remove this loop.

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D135847/new/

https://reviews.llvm.org/D135847