[PATCH] D157740: [WIP] [InstCombine] Fold icmp into phi beyond the same BB.

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:3899
     // not, we are just pessimizing the code by making an i1 phi.
-    if (LHSI->getParent() == I.getParent())
+    if (LHSI->getParent() == I.getParent() || isa<BinaryOperator>(LHSI->getOperand(0)))
       if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
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I don't think this special case make sense. Either we allow this, or we don't. There is no reason to believe that this is beneficial for just binary operators -- it just happens that this allows follow-on folds in your specific example.

I //am// open to dropping the check entirely, if we don't see any significant regressions from that.


Repository:
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  https://reviews.llvm.org/D157740/new/

https://reviews.llvm.org/D157740