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[NFC] Factor out utility function for finding common dom of user set

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This commit is contained in:
Max Kazantsev 2021-03-19 13:07:57 +07:00
parent 776d09a23c
commit 2ca3074b8b
1 changed files with 21 additions and 13 deletions
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34
lib/Transforms/Utils/SimplifyIndVar.cpp
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@ -1477,6 +1477,24 @@ bool WidenIV::widenLoopCompare(WidenIV::NarrowIVDefUse DU) {
return true;
}
/// Find a point in code which dominates all given instructions. We can safely
/// assume that, whatever fact we can prove at the found point, this fact is
/// also true for each of the given instructions.
static Instruction *findCommonDominator(ArrayRef<Instruction *> Instructions,
DominatorTree &DT) {
Instruction *CommonDom = nullptr;
for (auto *Insn : Instructions)
if (!CommonDom || DT.dominates(Insn, CommonDom))
CommonDom = Insn;
else if (!DT.dominates(CommonDom, Insn))
// If there is no dominance relation, use common dominator.
CommonDom =
DT.findNearestCommonDominator(CommonDom->getParent(),
Insn->getParent())->getTerminator();
assert(CommonDom && "Common dominator not found?");
return CommonDom;
}
// The widenIVUse avoids generating trunc by evaluating the use as AddRec, this
// will not work when:
// 1) SCEV traces back to an instruction inside the loop that SCEV can not
@ -1572,17 +1590,7 @@ bool WidenIV::widenWithVariantUse(WidenIV::NarrowIVDefUse DU) {
// We'll prove some facts that should be true in the context of ext users. If
// there is no users, we are done now. If there are some, pick their common
// dominator as context.
Instruction *Context = nullptr;
for (auto *Ext : ExtUsers) {
if (!Context || DT->dominates(Ext, Context))
Context = Ext;
else if (!DT->dominates(Context, Ext))
// For users that don't have dominance relation, use common dominator.
Context =
DT->findNearestCommonDominator(Context->getParent(), Ext->getParent())
->getTerminator();
}
assert(Context && "Context not found?");
const Instruction *CtxI = findCommonDominator(ExtUsers, *DT);
if (!CanSignExtend && !CanZeroExtend) {
// Because InstCombine turns 'sub nuw' to 'add' losing the no-wrap flag, we
@ -1598,8 +1606,8 @@ bool WidenIV::widenWithVariantUse(WidenIV::NarrowIVDefUse DU) {
return false;
if (!SE->isKnownNegative(RHS))
return false;
bool ProvedSubNUW = SE->isKnownPredicateAt(
ICmpInst::ICMP_UGE, LHS, SE->getNegativeSCEV(RHS), Context);
bool ProvedSubNUW = SE->isKnownPredicateAt(ICmpInst::ICMP_UGE, LHS,
SE->getNegativeSCEV(RHS), CtxI);
if (!ProvedSubNUW)
return false;
// In fact, our 'add' is 'sub nuw'. We will need to widen the 2nd operand as