[PATCH] D151816: [ValueTracking] Directly use KnownBits shift functions

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
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Make ValueTracking directly call the KnownBits shift helpers, which provides more precise results.

Unfortunately, ValueTracking has a special case where sometimes we determine non-zero shift amounts using isKnownNonZero(). I have my doubts about the usefulness of that special-case (it is only tested in a single unit test), but I've reproduced the special-case via an extra parameter to the KnownBits methods.


https://reviews.llvm.org/D151816

Files:
  llvm/include/llvm/Support/KnownBits.h
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/lib/Support/KnownBits.cpp
  llvm/test/Analysis/ScalarEvolution/extract-highbits-variablemask.ll
  llvm/test/Analysis/ScalarEvolution/extract-lowbits-variablemask.ll
  llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll
  llvm/test/Analysis/ValueTracking/known-power-of-two-urem.ll
  llvm/test/Transforms/IndVarSimplify/shift-range-checks.ll
  llvm/test/Transforms/InstCombine/zext-or-icmp.ll

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