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Add an RAII helper to make cleanup of the RecursionSet more fool-proof.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112628 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2010-08-31 19:24:27 +00:00
parent 869a144f4e
commit 9ba353627a
1 changed files with 24 additions and 18 deletions
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42
lib/Transforms/Scalar/JumpThreading.cpp
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@ -79,6 +79,20 @@ namespace {
SmallSet<AssertingVH<BasicBlock>, 16> LoopHeaders;
#endif
DenseSet<std::pair<Value*, BasicBlock*> > RecursionSet;
// RAII helper for updating the recursion stack.
struct RecursionSetRemover {
DenseSet<std::pair<Value*, BasicBlock*> > &TheSet;
std::pair<Value*, BasicBlock*> ThePair;
RecursionSetRemover(DenseSet<std::pair<Value*, BasicBlock*> > &S,
std::pair<Value*, BasicBlock*> P)
: TheSet(S), ThePair(P) { }
~RecursionSetRemover() {
TheSet.erase(ThePair);
}
};
public:
static char ID; // Pass identification
JumpThreading() : FunctionPass(ID) {}
@ -271,9 +285,17 @@ void JumpThreading::FindLoopHeaders(Function &F) {
///
bool JumpThreading::
ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
// This method walks up use-def chains recursively. Because of this, we could
// get into an infinite loop going around loops in the use-def chain. To
// prevent this, keep track of what (value, block) pairs we've already visited
// and terminate the search if we loop back to them
if (!RecursionSet.insert(std::make_pair(V, BB)).second)
return false;
// An RAII help to remove this pair from the recursion set once the recursion
// stack pops back out again.
RecursionSetRemover remover(RecursionSet, std::make_pair(V, BB));
// If V is a constantint, then it is known in all predecessors.
if (isa<ConstantInt>(V) || isa<UndefValue>(V)) {
ConstantInt *CI = dyn_cast<ConstantInt>(V);
@ -281,7 +303,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
Result.push_back(std::make_pair(CI, *PI));
RecursionSet.erase(std::make_pair(V, BB));
return true;
}
@ -316,11 +337,9 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
Result.push_back(std::make_pair(dyn_cast<ConstantInt>(PredCst), P));
}
RecursionSet.erase(std::make_pair(V, BB));
return !Result.empty();
}
RecursionSet.erase(std::make_pair(V, BB));
return false;
}
@ -344,7 +363,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
}
}
RecursionSet.erase(std::make_pair(V, BB));
return !Result.empty();
}
@ -359,10 +377,8 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
ComputeValueKnownInPredecessors(I->getOperand(0), BB, LHSVals);
ComputeValueKnownInPredecessors(I->getOperand(1), BB, RHSVals);
if (LHSVals.empty() && RHSVals.empty()) {
RecursionSet.erase(std::make_pair(V, BB));
if (LHSVals.empty() && RHSVals.empty())
return false;
}
ConstantInt *InterestingVal;
if (I->getOpcode() == Instruction::Or)
@ -390,7 +406,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
}
}
RecursionSet.erase(std::make_pair(V, BB));
return !Result.empty();
}
@ -399,10 +414,8 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
isa<ConstantInt>(I->getOperand(1)) &&
cast<ConstantInt>(I->getOperand(1))->isOne()) {
ComputeValueKnownInPredecessors(I->getOperand(0), BB, Result);
if (Result.empty()) {
RecursionSet.erase(std::make_pair(V, BB));
if (Result.empty())
return false;
}
// Invert the known values.
for (unsigned i = 0, e = Result.size(); i != e; ++i)
@ -410,7 +423,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
Result[i].first =
cast<ConstantInt>(ConstantExpr::getNot(Result[i].first));
RecursionSet.erase(std::make_pair(V, BB));
return true;
}
@ -439,7 +451,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
}
}
RecursionSet.erase(std::make_pair(V, BB));
return !Result.empty();
}
@ -473,7 +484,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
Result.push_back(std::make_pair(CI, PredBB));
}
RecursionSet.erase(std::make_pair(V, BB));
return !Result.empty();
}
@ -500,7 +510,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
Result.push_back(std::make_pair(cast<ConstantInt>(ResC), P));
}
RecursionSet.erase(std::make_pair(V, BB));
return !Result.empty();
}
@ -525,7 +534,6 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
Result.push_back(std::make_pair((ConstantInt*)0,LHSVals[i].second));
}
RecursionSet.erase(std::make_pair(V, BB));
return !Result.empty();
}
}
@ -540,11 +548,9 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
Result.push_back(std::make_pair(CInt, *PI));
}
RecursionSet.erase(std::make_pair(V, BB));
return !Result.empty();
}
RecursionSet.erase(std::make_pair(V, BB));
return false;
}