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[ValueTracking] Hoist some computation out of a loop; NFC 

There is no need to match the comparison instruction repeatedly.

llvm-svn: 268836
This commit is contained in:
Sanjoy Das 2016-05-07 02:08:24 +00:00
parent 5056e19fce
commit 987aaa1374
1 changed files with 11 additions and 20 deletions
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31
llvm/lib/Analysis/ValueTracking.cpp
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@ -3199,39 +3199,30 @@ static bool isKnownNonNullFromDominatingCondition(const Value *V,
assert(V->getType()->isPointerTy() && "V must be pointer type");
unsigned NumUsesExplored = 0;
for (auto U : V->users()) {
for (auto *U : V->users()) {
// Avoid massive lists
if (NumUsesExplored >= DomConditionsMaxUses)
break;
NumUsesExplored++;
// Consider only compare instructions uniquely controlling a branch
const ICmpInst *Cmp = dyn_cast<ICmpInst>(U);
if (!Cmp)
CmpInst::Predicate Pred;
if (!match(const_cast<User *>(U),
m_c_ICmp(Pred, m_Specific(V), m_Zero())) ||
(Pred != ICmpInst::ICMP_EQ && Pred != ICmpInst::ICMP_NE))
continue;
for (auto *CmpU : Cmp->users()) {
for (auto *CmpU : U->users()) {
const BranchInst *BI = dyn_cast<BranchInst>(CmpU);
if (!BI)
continue;
assert(BI->isConditional() && "uses a comparison!");
BasicBlock *NonNullSuccessor = nullptr;
CmpInst::Predicate Pred;
if (match(const_cast<ICmpInst*>(Cmp),
m_c_ICmp(Pred, m_Specific(V), m_Zero()))) {
if (Pred == ICmpInst::ICMP_EQ)
NonNullSuccessor = BI->getSuccessor(1);
else if (Pred == ICmpInst::ICMP_NE)
NonNullSuccessor = BI->getSuccessor(0);
}
if (NonNullSuccessor) {
BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor);
if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent()))
return true;
}
BasicBlock *NonNullSuccessor =
BI->getSuccessor(Pred == ICmpInst::ICMP_EQ ? 1 : 0);
BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor);
if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent()))
return true;
}
}