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Fix PR306: Loop simplify incorrectly updates dominator information

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Testcase: LoopSimplify/2004-04-01-IncorrectDomUpdate.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12592 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-04-01 19:06:07 +00:00
parent afd5e2fdec
commit 4f303bd4a5
1 changed files with 22 additions and 9 deletions
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31
lib/Transforms/Utils/LoopSimplify.cpp
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@ -530,9 +530,19 @@ void LoopSimplify::UpdateDomInfoForRevectoredPreds(BasicBlock *NewBB,
BasicBlock *NewBBSucc = *succ_begin(NewBB); BasicBlock *NewBBSucc = *succ_begin(NewBB);
DominatorSet &DS = getAnalysis<DominatorSet>(); DominatorSet &DS = getAnalysis<DominatorSet>();
// Update dominator information... The blocks that dominate NewBB are the
// intersection of the dominators of predecessors, plus the block itself.
//
DominatorSet::DomSetType NewBBDomSet = DS.getDominators(PredBlocks[0]);
for (unsigned i = 1, e = PredBlocks.size(); i != e; ++i)
set_intersect(NewBBDomSet, DS.getDominators(PredBlocks[i]));
NewBBDomSet.insert(NewBB); // All blocks dominate themselves...
DS.addBasicBlock(NewBB, NewBBDomSet);
// The newly inserted basic block will dominate existing basic blocks iff the // The newly inserted basic block will dominate existing basic blocks iff the
// PredBlocks dominate all of the non-pred blocks. If all predblocks dominate // PredBlocks dominate all of the non-pred blocks. If all predblocks dominate
// the non-pred blocks, then they all must be the same block! // the non-pred blocks, then they all must be the same block!
//
bool NewBBDominatesNewBBSucc = true; bool NewBBDominatesNewBBSucc = true;
{ {
BasicBlock *OnePred = PredBlocks[0]; BasicBlock *OnePred = PredBlocks[0];
@ -551,15 +561,18 @@ void LoopSimplify::UpdateDomInfoForRevectoredPreds(BasicBlock *NewBB,
} }
} }
// Update dominator information... The blocks that dominate NewBB are the // The other scenario where the new block can dominate its successors are when
// intersection of the dominators of predecessors, plus the block itself. // all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
// The newly created basic block does not dominate anything except itself. // already.
// if (!NewBBDominatesNewBBSucc) {
DominatorSet::DomSetType NewBBDomSet = DS.getDominators(PredBlocks[0]); NewBBDominatesNewBBSucc = true;
for (unsigned i = 1, e = PredBlocks.size(); i != e; ++i) for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
set_intersect(NewBBDomSet, DS.getDominators(PredBlocks[i])); PI != E; ++PI)
NewBBDomSet.insert(NewBB); // All blocks dominate themselves... if (*PI != NewBB && !DS.dominates(NewBBSucc, *PI)) {
DS.addBasicBlock(NewBB, NewBBDomSet); NewBBDominatesNewBBSucc = false;
break;
}
}
// If NewBB dominates some blocks, then it will dominate all blocks that // If NewBB dominates some blocks, then it will dominate all blocks that
// NewBBSucc does. // NewBBSucc does.