[PATCH] D56355: [InstCombine] Simplify cttz/ctlz + icmp ugt/ult into mask check

[Sanjay Patel via Phabricator via llvm-commits]

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

LGTM - see inline comment for minor improvement.



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Comment at: lib/Transforms/InstCombine/InstCombineCompares.cpp:2855
+
+    if (Cmp.getPredicate() == ICmpInst::ICMP_UGT && C.ult(BitWidth)) {
+      APInt Mask = APInt::getLowBitsSet(BitWidth, C.getLimitedValue() + 1);
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It would be nice to have a code comment that shows the general transform formula and/or an example of how this works based on the regression tests. Seeing those makes it clear, but it's not obvious to me just looking at the code.


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https://reviews.llvm.org/D56355