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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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20
include/llvm/Analysis/Dominators.h
View File

@ -438,6 +438,26 @@ public:
/// frontier to reflect this change.
void splitBlock(BasicBlock *BB);
/// BasicBlock BB's new dominator is NewBB. Update BB's dominance frontier
/// to reflect this change.
void changeImmediateDominator(BasicBlock *BB, BasicBlock *NewBB,
DominatorTree *DT) {
// NewBB is now dominating BB. Which means BB's dominance
// frontier is now part of NewBB's dominance frontier. However, BB
// itself is not member of NewBB's dominance frontier.
DominanceFrontier::iterator NewDFI = find(NewBB);
DominanceFrontier::iterator DFI = find(BB);
DominanceFrontier::DomSetType BBSet = DFI->second;
for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(),
BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) {
BasicBlock *DFMember = *BBSetI;
// Insert only if NewBB dominates DFMember.
if (!DT->dominates(NewBB, DFMember))
NewDFI->second.insert(DFMember);
}
NewDFI->second.erase(BB);
}
private:
const DomSetType &calculate(const DominatorTree &DT,
const DomTreeNode *Node);

63
lib/Transforms/Scalar/LoopIndexSplit.cpp
View File

@ -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();

3
lib/Transforms/Utils/LCSSA.cpp
View File

@ -107,7 +107,8 @@ bool LCSSA::runOnLoop(Loop *L, LPPassManager &LPM) {
LI = &LPM.getAnalysis<LoopInfo>();
DT = &getAnalysis<DominatorTree>();
DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>();
// Speed up queries by creating a sorted list of blocks
LoopBlocks.clear();
LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end());