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Fix dominance frontier update while removing blocks. 

llvm-svn: 41082
This commit is contained in:
Devang Patel 2007-08-14 18:35:57 +00:00
parent bc271a02fd
commit 33ba97d747
1 changed files with 30 additions and 7 deletions
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37
llvm/lib/Transforms/Scalar/LoopIndexSplit.cpp
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@ -97,8 +97,10 @@ namespace {
/// loop may not be eliminated. /// loop may not be eliminated.
bool safeExitBlock(SplitInfo &SD, BasicBlock *BB); bool safeExitBlock(SplitInfo &SD, BasicBlock *BB);
/// removeBlocks - Remove basic block BB and all blocks dominated by BB. /// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB.
void removeBlocks(BasicBlock *InBB, Loop *LP); /// This routine is used to remove split condition's dead branch, dominated by
/// DeadBB. LiveBB dominates split conidition's other branch.
void removeBlocks(BasicBlock *DeadBB, Loop *LP, BasicBlock *LiveBB);
/// Find cost of spliting loop L. /// Find cost of spliting loop L.
unsigned findSplitCost(Loop *L, SplitInfo &SD); unsigned findSplitCost(Loop *L, SplitInfo &SD);
@ -589,11 +591,14 @@ unsigned LoopIndexSplit::findSplitCost(Loop *L, SplitInfo &SD) {
return Cost; return Cost;
} }
/// removeBlocks - Remove basic block BB and all blocks dominated by BB. /// removeBlocks - Remove basic block DeadBB and all blocks dominated by DeadBB.
void LoopIndexSplit::removeBlocks(BasicBlock *InBB, Loop *LP) { /// This routine is used to remove split condition's dead branch, dominated by
/// DeadBB. LiveBB dominates split conidition's other branch.
void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
BasicBlock *LiveBB) {
SmallVector<std::pair<BasicBlock *, succ_iterator>, 8> WorkList; SmallVector<std::pair<BasicBlock *, succ_iterator>, 8> WorkList;
WorkList.push_back(std::make_pair(InBB, succ_begin(InBB))); WorkList.push_back(std::make_pair(DeadBB, succ_begin(DeadBB)));
while (!WorkList.empty()) { while (!WorkList.empty()) {
BasicBlock *BB = WorkList.back(). first; BasicBlock *BB = WorkList.back(). first;
succ_iterator SIter =WorkList.back().second; succ_iterator SIter =WorkList.back().second;
@ -630,10 +635,28 @@ void LoopIndexSplit::removeBlocks(BasicBlock *InBB, Loop *LP) {
break; break;
} }
DT->changeImmediateDominator(SuccBB, LiveBB);
// If BB is not dominating SuccBB then SuccBB is in BB's dominance // If BB is not dominating SuccBB then SuccBB is in BB's dominance
// frontiner. // frontiner.
DominanceFrontier::iterator BBDF = DF->find(BB); DominanceFrontier::iterator BBDF = DF->find(BB);
DF->removeFromFrontier(BBDF, SuccBB); DF->removeFromFrontier(BBDF, SuccBB);
// LiveBB is now dominating SuccBB. Which means SuccBB's dominance
// frontier is member of LiveBB's dominance frontier. However, SuccBB
// itself is not member of LiveBB's dominance frontier.
DominanceFrontier::iterator LiveDF = DF->find(LiveBB);
DominanceFrontier::iterator SuccDF = DF->find(SuccBB);
DominanceFrontier::DomSetType SuccBBSet = SuccDF->second;
for (DominanceFrontier::DomSetType::iterator SuccBBSetI = SuccBBSet.begin(),
SuccBBSetE = SuccBBSet.end(); SuccBBSetI != SuccBBSetE; ++SuccBBSetI) {
BasicBlock *DFMember = *SuccBBSetI;
// Insert only if LiveBB dominates DFMember.
if (!DT->dominates(LiveBB, DFMember))
LiveDF->second.insert(DFMember);
}
DF->removeFromFrontier(LiveDF, SuccBB);
} }
} }
} }
@ -747,7 +770,7 @@ bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
BranchInst *BR = cast<BranchInst>(SplitBlock->getTerminator()); BranchInst *BR = cast<BranchInst>(SplitBlock->getTerminator());
BasicBlock *FBB = BR->getSuccessor(1); BasicBlock *FBB = BR->getSuccessor(1);
BR->setUnconditionalDest(BR->getSuccessor(0)); BR->setUnconditionalDest(BR->getSuccessor(0));
removeBlocks(FBB, L); removeBlocks(FBB, L, BR->getSuccessor(0));
//[*] Update True loop's exit value using new exit value. //[*] Update True loop's exit value using new exit value.
ExitCondition->setOperand(ExitValueNum, TLExitValue); ExitCondition->setOperand(ExitValueNum, TLExitValue);
@ -757,7 +780,7 @@ bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
BranchInst *FBR = cast<BranchInst>(FSplitBlock->getTerminator()); BranchInst *FBR = cast<BranchInst>(FSplitBlock->getTerminator());
BasicBlock *TBB = FBR->getSuccessor(0); BasicBlock *TBB = FBR->getSuccessor(0);
FBR->setUnconditionalDest(FBR->getSuccessor(1)); FBR->setUnconditionalDest(FBR->getSuccessor(1));
removeBlocks(TBB, FalseLoop); removeBlocks(TBB, FalseLoop, cast<BasicBlock>(FBR->getSuccessor(0)));
return true; return true;
} }