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Delay dominator updation while cloning loop.

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Summary:
Dominator updation fails for a loop inserted with a new basicblock.

A block required by DT to set the IDom might not have been cloned yet. This is because there is no predefined ordering of loop blocks (except for the header block which should be the first block in the list).

The patch first creates DT nodes for the cloned blocks and then separately updates the DT in a follow-on loop.

Reviewers: anemet, dberlin

Subscribers: dberlin, llvm-commits

Differential Revision: http://reviews.llvm.org/D20899

llvm-svn: 272479
This commit is contained in:
Vikram TV 2016-06-11 16:41:10 +00:00
parent b7726309b9
commit b4ecab0885
1 changed files with 9 additions and 3 deletions
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12
lib/Transforms/Utils/CloneFunction.cpp
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@ -688,13 +688,19 @@ Loop *llvm::cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
// Update LoopInfo.
NewLoop->addBasicBlockToLoop(NewBB, *LI);
// Update DominatorTree.
BasicBlock *IDomBB = DT->getNode(BB)->getIDom()->getBlock();
DT->addNewBlock(NewBB, cast<BasicBlock>(VMap[IDomBB]));
// Add DominatorTree node. After seeing all blocks, update to correct IDom.
DT->addNewBlock(NewBB, NewPH);
Blocks.push_back(NewBB);
}
for (BasicBlock *BB : OrigLoop->getBlocks()) {
// Update DominatorTree.
BasicBlock *IDomBB = DT->getNode(BB)->getIDom()->getBlock();
DT->changeImmediateDominator(cast<BasicBlock>(VMap[BB]),
cast<BasicBlock>(VMap[IDomBB]));
}
// Move them physically from the end of the block list.
F->getBasicBlockList().splice(Before->getIterator(), F->getBasicBlockList(),
NewPH);