[all-commits] [llvm/llvm-project] 77eb05: [InstCombine] Simplify select using KnownBits of c...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 77eb05683082dd3751ccfab963f5160f1852058d
      https://github.com/llvm/llvm-project/commit/77eb05683082dd3751ccfab963f5160f1852058d
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2024-07-01 (Mon, 01 Jul 2024)

  Changed paths:
    M llvm/include/llvm/Analysis/SimplifyQuery.h
    M llvm/lib/Analysis/ValueTracking.cpp
    M llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
    M llvm/test/Transforms/InstCombine/select-binop-cmp.ll
    M llvm/test/Transforms/InstCombine/select-of-bittest.ll
    M llvm/test/Transforms/InstCombine/select.ll
    M llvm/test/Transforms/LoopVectorize/interleaved-accesses-pred-stores.ll

  Log Message:
  -----------
  [InstCombine] Simplify select using KnownBits of condition (#95923)

Simplify the arms of a select based on the KnownBits implied by its condition.
For now this only handles the case where the select arm folds to a constant,
but this can be generalized to handle other patterns by using
SimplifyDemandedBits instead (in that case we would also have to limit to
non-undef conditions).

This is implemented by adding a new member to SimplifyQuery that can be used
to inject an additional condition. The affected values are pre-computed and
we don't call computeKnownBits() if the select arms don't contain affected
values. This reduces the cost in some pathological cases.



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