[all-commits] [llvm/llvm-project] f37ab1: [InstCombine] Infer exact for lshr by cttz (#136696)

[黃國庭 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f37ab152540d374ceff8551abef3de5110e697ee
      https://github.com/llvm/llvm-project/commit/f37ab152540d374ceff8551abef3de5110e697ee
  Author: 黃國庭 <we3223 at gmail.com>
  Date:   2025-04-29 (Tue, 29 Apr 2025)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
    A llvm/test/Transforms/InstCombine/cttz-shift-exact.ll
    M llvm/test/Transforms/InstCombine/select.ll

  Log Message:
  -----------
  [InstCombine] Infer exact for lshr by cttz (#136696)

Infer the 'exact' flag on an 'lshr' or 'ashr' instruction when the shift
amount is computed via a 'cttz' intrinsic on the same operand.
 
Proof: https://alive2.llvm.org/ce/z/CQR2PG

Fixes #131444.



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