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Disable PRE for landing pads.

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PRE needs the landing pads to have their critical edges split. Doing this for a
landing pad is non-trivial. Abandon the attempt to perform PRE when we come
across a landing pad. (Reviewed by Owen!)

llvm-svn: 137876
This commit is contained in:
Bill Wendling 2011-08-17 21:32:02 +00:00
parent 2b25bb15ec
commit fa8d0e1aea
1 changed files with 14 additions and 2 deletions
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16
lib/Transforms/Scalar/GVN.cpp
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@ -1446,8 +1446,8 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i) for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
Blockers.insert(UnavailableBlocks[i]); Blockers.insert(UnavailableBlocks[i]);
// Lets find first basic block with more than one predecessor. Walk backwards // Let's find the first basic block with more than one predecessor. Walk
// through predecessors if needed. // backwards through predecessors if needed.
BasicBlock *LoadBB = LI->getParent(); BasicBlock *LoadBB = LI->getParent();
BasicBlock *TmpBB = LoadBB; BasicBlock *TmpBB = LoadBB;
@ -1519,10 +1519,19 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
<< Pred->getName() << "': " << *LI << '\n'); << Pred->getName() << "': " << *LI << '\n');
return false; return false;
} }
if (LoadBB->isLandingPad()) {
DEBUG(dbgs()
<< "COULD NOT PRE LOAD BECAUSE OF LANDING PAD CRITICAL EDGE '"
<< Pred->getName() << "': " << *LI << '\n');
return false;
}
unsigned SuccNum = GetSuccessorNumber(Pred, LoadBB); unsigned SuccNum = GetSuccessorNumber(Pred, LoadBB);
NeedToSplit.push_back(std::make_pair(Pred->getTerminator(), SuccNum)); NeedToSplit.push_back(std::make_pair(Pred->getTerminator(), SuccNum));
} }
} }
if (!NeedToSplit.empty()) { if (!NeedToSplit.empty()) {
toSplit.append(NeedToSplit.begin(), NeedToSplit.end()); toSplit.append(NeedToSplit.begin(), NeedToSplit.end());
return false; return false;
@ -2071,6 +2080,9 @@ bool GVN::performPRE(Function &F) {
// Nothing to PRE in the entry block. // Nothing to PRE in the entry block.
if (CurrentBlock == &F.getEntryBlock()) continue; if (CurrentBlock == &F.getEntryBlock()) continue;
// Don't perform PRE on a landing pad.
if (CurrentBlock->isLandingPad()) continue;
for (BasicBlock::iterator BI = CurrentBlock->begin(), for (BasicBlock::iterator BI = CurrentBlock->begin(),
BE = CurrentBlock->end(); BI != BE; ) { BE = CurrentBlock->end(); BI != BE; ) {
Instruction *CurInst = BI++; Instruction *CurInst = BI++;