[PATCH] D103788: [InstCombine] Eliminate casts to optimize ctlz operation

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp:955
+  if (match(Src, m_OneUse(m_Intrinsic<Intrinsic::ctlz>(
+                     m_OneUse(m_ZExt(m_Value(A))), m_Value(B))))) {
+    Value *WidthDiff =
----------------
I don't think we need this one-use check on the zext. Usually, we say that if we are not increasing the instruction count, but we are reducing the sequence of computation, it's ok to do the transform.

This will be easier to see if we commit the tests with the baseline CHECKs, so I pushed those to main:
9eef6e39816a

Please rebase and regenerate the CHECK lines (and see if it's ok to remove the 2nd one-use check).


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D103788/new/

https://reviews.llvm.org/D103788