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[IR] Don't create ptrtoint expression to determine alignment (NFCI) #161364

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Merged
merged 1 commit into from
Sep 30, 2025
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[IR] Don't create ptrtoint expression to determine alignment (NFCI) #161364

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14 changes: 6 additions & 8 deletions llvm/lib/IR/Value.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1000,14 +1000,12 @@ Align Value::getPointerAlignment(const DataLayout &DL) const {
ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
return Align(CI->getLimitedValue());
}
} else if (auto *CstPtr = dyn_cast<Constant>(this)) {
// Strip pointer casts to avoid creating unnecessary ptrtoint expression
// if the only "reduction" is combining a bitcast + ptrtoint.
CstPtr = CstPtr->stripPointerCasts();
if (auto *CstInt = dyn_cast_or_null<ConstantInt>(ConstantExpr::getPtrToInt(
const_cast<Constant *>(CstPtr), DL.getIntPtrType(getType()),
/*OnlyIfReduced=*/true))) {
size_t TrailingZeros = CstInt->getValue().countr_zero();
} else if (auto *CE = dyn_cast<ConstantExpr>(this)) {
// Determine the alignment of inttoptr(C).
if (CE->getOpcode() == Instruction::IntToPtr &&
isa<ConstantInt>(CE->getOperand(0))) {
ConstantInt *IntPtr = cast<ConstantInt>(CE->getOperand(0));
size_t TrailingZeros = IntPtr->getValue().countr_zero();
// While the actual alignment may be large, elsewhere we have
// an arbitrary upper alignmet limit, so let's clamp to it.
return Align(TrailingZeros < Value::MaxAlignmentExponent
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