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When one branch of condition is eliminated then head of the other

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branch is not necessary immediate dominators of merge blcok in all cases.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41144 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel
2007-08-17 21:59:16 +00:00
parent 3e20bba5eb
commit 96bf524b53
3 changed files with 64 additions and 22 deletions
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lib/Transforms/Scalar/LoopIndexSplit.cpp
+42 -21
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@@ -603,6 +603,7 @@ void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
BasicBlock *LiveBB) {
// First update DeadBB's dominance frontier.
SmallVector<BasicBlock *, 8> FrontierBBs;
DominanceFrontier::iterator DeadBBDF = DF->find(DeadBB);
if (DeadBBDF != DF->end()) {
SmallVector<BasicBlock *, 8> PredBlocks;
@@ -611,7 +612,8 @@ void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
for (DominanceFrontier::DomSetType::iterator DeadBBSetI = DeadBBSet.begin(),
DeadBBSetE = DeadBBSet.end(); DeadBBSetI != DeadBBSetE; ++DeadBBSetI) {
BasicBlock *FrontierBB = *DeadBBSetI;
FrontierBBs.push_back(FrontierBB);
// Rremove any PHI incoming edge from blocks dominated by DeadBB.
PredBlocks.clear();
for(pred_iterator PI = pred_begin(FrontierBB), PE = pred_end(FrontierBB);
@@ -620,7 +622,8 @@ void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
if (P == DeadBB || DT->dominates(DeadBB, P))
PredBlocks.push_back(P);
}
BasicBlock *NewDominator = NULL;
for(BasicBlock::iterator FBI = FrontierBB->begin(), FBE = FrontierBB->end();
FBI != FBE; ++FBI) {
if (PHINode *PN = dyn_cast<PHINode>(FBI)) {
@@ -629,27 +632,14 @@ void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
BasicBlock *P = *PI;
PN->removeIncomingValue(P);
}
// If we have not identified new dominator then see if we can identify
// one based on remaining incoming PHINode values.
if (NewDominator == NULL && PN->getNumIncomingValues() == 1)
NewDominator = PN->getIncomingBlock(0);
}
else
break;
}
DT->changeImmediateDominator(FrontierBB, LiveBB);
// LiveBB is now dominating FrontierBB. Which means FrontierBB's dominance
// frontier is member of LiveBB's dominance frontier. However, FrontierBB
// itself is not member of LiveBB's dominance frontier.
DominanceFrontier::iterator LiveDF = DF->find(LiveBB);
DominanceFrontier::iterator FrontierDF = DF->find(FrontierBB);
DominanceFrontier::DomSetType FrontierBBSet = FrontierDF->second;
for (DominanceFrontier::DomSetType::iterator FrontierBBSetI = FrontierBBSet.begin(),
FrontierBBSetE = FrontierBBSet.end(); FrontierBBSetI != FrontierBBSetE; ++FrontierBBSetI) {
BasicBlock *DFMember = *FrontierBBSetI;
// Insert only if LiveBB dominates DFMember.
if (!DT->dominates(LiveBB, DFMember))
LiveDF->second.insert(DFMember);
}
LiveDF->second.erase(FrontierBB);
}
}
}
@@ -660,7 +650,7 @@ void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
E = df_end(DN); DI != E; ++DI) {
BasicBlock *BB = DI->getBlock();
WorkList.push_back(BB);
BB->getTerminator()->eraseFromParent();
BB->replaceAllUsesWith(UndefValue::get(Type::LabelTy));
}
while (!WorkList.empty()) {
@@ -677,6 +667,31 @@ void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
LI->removeBlock(BB);
BB->eraseFromParent();
}
// Update Frontier BBs' dominator info.
while (!FrontierBBs.empty()) {
BasicBlock *FBB = FrontierBBs.back(); FrontierBBs.pop_back();
BasicBlock *NewDominator = FBB->getSinglePredecessor();
if (!NewDominator) {
pred_iterator PI = pred_begin(FBB), PE = pred_end(FBB);
NewDominator = *PI;
++PI;
if (NewDominator != LiveBB) {
for(; PI != PE; ++PI) {
BasicBlock *P = *PI;
if (P == LiveBB) {
NewDominator = LiveBB;
break;
}
NewDominator = DT->findNearestCommonDominator(NewDominator, P);
}
}
}
assert (NewDominator && "Unable to fix dominator info.");
DT->changeImmediateDominator(FBB, NewDominator);
DF->changeImmediateDominator(FBB, NewDominator, DT);
}
}
bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
@@ -696,6 +711,12 @@ bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
|| Latch == SplitTerminator->getSuccessor(1)))
return false;
BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
if (DT->dominates(Succ0, Latch) || DT->dominates(Succ1, Latch))
return false;
// True loop is original loop. False loop is cloned loop.
bool SignedPredicate = ExitCondition->isSignedPredicate();