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Fix SimplifyCFG/2005-12-03-IncorrectPHIFold.ll

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llvm-svn: 24581
This commit is contained in:
Chris Lattner 2005-12-03 18:25:58 +00:00
parent 523b163d74
commit f9a1c37c84
1 changed files with 14 additions and 8 deletions
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22
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -82,7 +82,7 @@ static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
//
if (isa<PHINode>(Succ->front())) {
std::set<BasicBlock*> BBPreds(pred_begin(BB), pred_end(BB));
for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);\
for (pred_iterator PI = pred_begin(Succ), PE = pred_end(Succ);
PI != PE; ++PI)
if (std::find(BBPreds.begin(), BBPreds.end(), *PI) != BBPreds.end()) {
// Loop over all of the PHI nodes checking to see if there are
@ -115,19 +115,25 @@ static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
}
if (IsSafe) return true;
// If the PHI nodes in BB are only used by instructions in Succ, we are ok.
IsSafe = true;
// If the PHI nodes in BB are only used by instructions in Succ, we are ok if
// BB and Succ have no common predecessors.
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I) && IsSafe; ++I) {
PHINode *PN = cast<PHINode>(I);
for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E;
++UI)
if (cast<Instruction>(*UI)->getParent() != Succ) {
IsSafe = false;
break;
}
if (cast<Instruction>(*UI)->getParent() != Succ)
return false;
}
return IsSafe;
// Scan the predecessor sets of BB and Succ, making sure there are no common
// predecessors. Common predecessors would cause us to build a phi node with
// differing incoming values, which is not legal.
std::set<BasicBlock*> BBPreds(pred_begin(BB), pred_end(BB));
for (pred_iterator PI = pred_begin(Succ), E = pred_end(Succ); PI != E; ++PI)
if (BBPreds.count(*PI))
return false;
return true;
}
/// TryToSimplifyUncondBranchFromEmptyBlock - BB contains an unconditional