diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp index d4f325cd46828..246bc0adaf6c8 100644 --- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp @@ -772,17 +772,20 @@ bool SimplifyIndvar::strengthenOverflowingOperation(BinaryOperator *BO, if (!BO->hasNoUnsignedWrap() && willNotOverflow(SE, BO->getOpcode(), /* Signed */ false, LHS, RHS)) { BO->setHasNoUnsignedWrap(); - SE->forgetValue(BO); Changed = true; } if (!BO->hasNoSignedWrap() && willNotOverflow(SE, BO->getOpcode(), /* Signed */ true, LHS, RHS)) { BO->setHasNoSignedWrap(); - SE->forgetValue(BO); Changed = true; } + // The willNotOverflow() check might infer additional nowrap flags on addrecs + // while performing zero/sign extensions. We could call forgetValue() here + // to make sure those flags also propagate to any other SCEV expressions + // based on the addrec. However, this can have pathological compile-time + // impact, see https://bugs.llvm.org/show_bug.cgi?id=50384. return Changed; }