[PATCH] D104665: [instcombine] Fold overflow check using umulo to comparison

[Philip Reames via Phabricator via llvm-commits]

reames created this revision.
reames added reviewers: spatel, craig.topper.
Herald added subscribers: javed.absar, bollu, hiraditya, mcrosier.
reames requested review of this revision.
Herald added a project: LLVM.

If we have a umul.with.overflow where the multiply result is not used and one of the operands is a constant, we can perform the overflow check cheaper with a comparison then by performing the multiply an extracting the overflow flag.

(Noticed when looking at the conditions SCEV emits for overflow checks.)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104665

Files:
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
  llvm/test/Transforms/InstCombine/umulo.ll

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