[PATCH] D99203: [RISCV] Add TTI support for cpop with Zbb

[Fraser Cormack via Phabricator via llvm-commits]

frasercrmck accepted this revision.
frasercrmck added a comment.
This revision is now accepted and ready to land.

LGTM



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Comment at: llvm/test/Transforms/LoopIdiom/RISCV/popcnt.ll:29
+; CPOP-NEXT:    br i1 [[TMP2]], label [[WHILE_END:%.*]], label [[WHILE_BODY_PREHEADER:%.*]]
+; CPOP:       while.body.preheader:
+; CPOP-NEXT:    br label [[WHILE_BODY:%.*]]
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craig.topper wrote:
> frasercrmck wrote:
> > Maybe it's late in the day but I expected there not to be a loop here. Am I missing something?
> LoopIdiomRecognize requires other passes to do the cleanup. The main goal of LoopIdiomRecognize is to rewrite the loop  into countable form. It does this by putting the ctpop outside the loop and decrement it each iteration. Other passes will need to determine that the loop doesn't do anything else and remove it.
Oh yes I see now how the PHIs in `while.end.loopexit` and `while.end` help show that. Thanks!


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https://reviews.llvm.org/D99203