[PATCH] D51112: [ValueTracking] Teach computeNumSignBits to understand min/max clamp patterns with constant/splat values

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: spatel, RKSimon, majnemer.

If we have a min/max pair we can do a better job of counting sign bits if we look at them together. This is similar to what is done in the SelectionDAG version of computeNumSignBits for ISD::SMAX/SMIN.

I'm not entirely sure if we can assume the constant is canonicalized to the RHS. So let me know if I need to handle that.

I'm still calling computeNumSignBits on the other input. I don't think SelectionDAG does that. Should the depth limit be bumped by 2 since we went through 2 nodes?


https://reviews.llvm.org/D51112

Files:
  lib/Analysis/ValueTracking.cpp
  test/Transforms/InstCombine/max_known_bits.ll

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