[PATCH] D83392: Strlen loop idiom recognition

[Muhammad Usman via Phabricator via llvm-commits]

musman marked an inline comment as done.
musman added inline comments.


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Comment at: llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp:1657
+  // Find the 'sub' instruction that computes the strlen. First we need
+  // the base pointer to check the operands of the 'sub'.
+  auto *BasePtrSCEV = dyn_cast<SCEVUnknown>(SE->getPointerBase(LoadEv));
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efriedma wrote:
> I don't understand what you're doing here.
> 
> Probably the simplest thing to do here would be to directly expand LCSSAPHI based on the result of strlen, instead of trying to dig into the exit block and find a subtraction operation.
I was thinking the subtraction operation was needed in order to do replaceAllUsesWith on it, is there a way to do that without needing the subtract?
Also, to expand the LCSSAPHI would you take the incoming value and check if it's an AddRec, then expand that?
Thanks again.


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  https://reviews.llvm.org/D83392/new/

https://reviews.llvm.org/D83392