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Fix loop-index-split to correctly preserve dominance frontiers. Part of

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PR4238.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72244 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2009-05-22 03:22:46 +00:00
parent 7eaf057e54
commit f7cca7b8f8
1 changed files with 12 additions and 17 deletions
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29
lib/Transforms/Scalar/LoopIndexSplit.cpp
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@ -349,11 +349,8 @@ bool LoopIndexSplit::processOneIterationLoop() {
// If BR operands are not IV or not loop invariants then skip this loop.
Value *OPV = SplitCondition->getOperand(0);
Value *SplitValue = SplitCondition->getOperand(1);
if (!L->isLoopInvariant(SplitValue)) {
Value *T = SplitValue;
SplitValue = OPV;
OPV = T;
}
if (!L->isLoopInvariant(SplitValue))
std::swap(OPV, SplitValue);
if (!L->isLoopInvariant(SplitValue))
return false;
Instruction *OPI = dyn_cast<Instruction>(OPV);
@ -783,25 +780,23 @@ void LoopIndexSplit::moveExitCondition(BasicBlock *CondBB, BasicBlock *ActiveBB,
// ExitBB is now dominated by CondBB
DT->changeImmediateDominator(ExitBB, CondBB);
DF->changeImmediateDominator(ExitBB, CondBB, DT);
// Basicblocks dominated by ActiveBB may have ExitingBB or
// a basic block outside the loop in their DF list. If so,
// replace it with CondBB.
DomTreeNode *Node = DT->getNode(ActiveBB);
for (df_iterator<DomTreeNode *> DI = df_begin(Node), DE = df_end(Node);
DI != DE; ++DI) {
BasicBlock *BB = DI->getBlock();
DominanceFrontier::iterator BBDF = DF->find(BB);
// Blocks outside the loop may have been in the dominance frontier of blocks
// inside the condition; this is now impossible because the blocks inside the
// condition no loger dominate the exit. Remove the relevant blocks from
// the dominance frontiers.
for (Loop::block_iterator I = LP->block_begin(), E = LP->block_end();
I != E; ++I) {
if (*I == CondBB || !DT->dominates(CondBB, *I)) continue;
DominanceFrontier::iterator BBDF = DF->find(*I);
DominanceFrontier::DomSetType::iterator DomSetI = BBDF->second.begin();
DominanceFrontier::DomSetType::iterator DomSetE = BBDF->second.end();
while (DomSetI != DomSetE) {
DominanceFrontier::DomSetType::iterator CurrentItr = DomSetI;
++DomSetI;
BasicBlock *DFBB = *CurrentItr;
if (DFBB == ExitingBB || !L->contains(DFBB)) {
if (!LP->contains(DFBB))
BBDF->second.erase(DFBB);
BBDF->second.insert(CondBB);
}
}
}
}