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Move domtree/frontier updating earlier, allowing us to use it to update phi

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nodes, removing a hack.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50019 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-04-21 01:05:08 +00:00
parent b85979434d
commit 1b58678d54
1 changed files with 18 additions and 31 deletions
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49
lib/Transforms/Utils/LoopSimplify.cpp
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@ -277,6 +277,19 @@ BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB,
// The preheader first gets an unconditional branch to the loop header. // The preheader first gets an unconditional branch to the loop header.
BranchInst *BI = BranchInst::Create(BB, NewBB); BranchInst *BI = BranchInst::Create(BB, NewBB);
// Move the edges from Preds to point to NewBB instead of BB.
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
if (Preds[i]->getUnwindDest() == BB)
Preds[i]->setUnwindDest(NewBB);
}
// Update dominator tree and dominator frontier if available.
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
DF->splitBlock(NewBB);
// For every PHI node in the block, insert a PHI node into NewBB where the // For every PHI node in the block, insert a PHI node into NewBB where the
// incoming values from the out of loop edges are moved to NewBB. We have two // incoming values from the out of loop edges are moved to NewBB. We have two
// possible cases here. If the loop is dead, we just insert dummy entries // possible cases here. If the loop is dead, we just insert dummy entries
@ -284,15 +297,9 @@ BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB,
// incoming edges in BB into new PHI nodes in NewBB. // incoming edges in BB into new PHI nodes in NewBB.
// //
if (Preds.empty()) { // Is the loop obviously dead? if (Preds.empty()) { // Is the loop obviously dead?
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I) { // Insert dummy values as the incoming value.
PHINode *PN = cast<PHINode>(I); for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
// Insert dummy values as the incoming value... cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
PN->addIncoming(Constant::getNullValue(PN->getType()), NewBB);
}
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
DF->splitBlock(NewBB);
return NewBB; return NewBB;
} }
@ -339,34 +346,14 @@ BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB,
// Can we eliminate this phi node now? // Can we eliminate this phi node now?
if (Value *V = PN->hasConstantValue(true)) { if (Value *V = PN->hasConstantValue(true)) {
Instruction *I = dyn_cast<Instruction>(V); Instruction *I = dyn_cast<Instruction>(V);
// If I is in NewBB, the Dominator call will fail, because NewBB isn't if (!I || DT->dominates(I, PN)) {
// registered in DominatorTree yet. Handle this case explicitly.
if (!I || (I->getParent() != NewBB &&
DT->dominates(I, PN))) {
PN->replaceAllUsesWith(V); PN->replaceAllUsesWith(V);
if (AA) AA->deleteValue(PN); if (AA) AA->deleteValue(PN);
BB->getInstList().erase(PN); PN->eraseFromParent();
} }
} }
} }
// Now that the PHI nodes are updated, actually move the edges from
// Preds to point to NewBB instead of BB.
//
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
TerminatorInst *TI = Preds[i]->getTerminator();
for (unsigned s = 0, e = TI->getNumSuccessors(); s != e; ++s)
if (TI->getSuccessor(s) == BB)
TI->setSuccessor(s, NewBB);
if (Preds[i]->getUnwindDest() == BB)
Preds[i]->setUnwindDest(NewBB);
}
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
DF->splitBlock(NewBB);
return NewBB; return NewBB;
} }