getAvailableVals(AV)[BB] = V;
}
+/// IsEquivalentPHI - Check if PHI has the same incoming value as specified
+/// in ValueMapping for each predecessor block.
+static bool IsEquivalentPHI(PHINode *PHI,
+ DenseMap<BasicBlock*, Value*> &ValueMapping) {
+ unsigned PHINumValues = PHI->getNumIncomingValues();
+ if (PHINumValues != ValueMapping.size())
+ return false;
+
+ // Scan the phi to see if it matches.
+ for (unsigned i = 0, e = PHINumValues; i != e; ++i)
+ if (ValueMapping[PHI->getIncomingBlock(i)] !=
+ PHI->getIncomingValue(i)) {
+ return false;
+ }
+
+ return true;
+}
+
+/// GetExistingPHI - Check if BB already contains a phi node that is equivalent
+/// to the specified mapping from predecessor blocks to incoming values.
+static Value *GetExistingPHI(BasicBlock *BB,
+ DenseMap<BasicBlock*, Value*> &ValueMapping) {
+ PHINode *SomePHI;
+ for (BasicBlock::iterator It = BB->begin();
+ (SomePHI = dyn_cast<PHINode>(It)); ++It) {
+ if (IsEquivalentPHI(SomePHI, ValueMapping))
+ return SomePHI;
+ }
+ return 0;
+}
+
+/// GetExistingPHI - Check if BB already contains an equivalent phi node.
+/// The InputIt type must be an iterator over std::pair<BasicBlock*, Value*>
+/// objects that specify the mapping from predecessor blocks to incoming values.
+template<typename InputIt>
+static Value *GetExistingPHI(BasicBlock *BB, const InputIt &I,
+ const InputIt &E) {
+ // Avoid create the mapping if BB has no phi nodes at all.
+ if (!isa<PHINode>(BB->begin()))
+ return 0;
+ DenseMap<BasicBlock*, Value*> ValueMapping(I, E);
+ return GetExistingPHI(BB, ValueMapping);
+}
+
/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
/// live at the end of the specified block.
Value *SSAUpdater::GetValueAtEndOfBlock(BasicBlock *BB) {
if (SingularValue != 0)
return SingularValue;
- // Otherwise, we do need a PHI: insert one now.
+ // Otherwise, we do need a PHI.
+ if (Value *ExistingPHI = GetExistingPHI(BB, PredValues.begin(),
+ PredValues.end()))
+ return ExistingPHI;
+
+ // Ok, we have no way out, insert a new one now.
PHINode *InsertedPHI = PHINode::Create(PrototypeValue->getType(),
PrototypeValue->getName(),
&BB->front());
// If the client wants to know about all new instructions, tell it.
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
- DEBUG(errs() << " Inserted PHI: " << *InsertedPHI << "\n");
+ DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
return InsertedPHI;
}
/// which use their value in the corresponding predecessor.
void SSAUpdater::RewriteUse(Use &U) {
Instruction *User = cast<Instruction>(U.getUser());
- BasicBlock *UseBB = User->getParent();
+
+ Value *V;
if (PHINode *UserPN = dyn_cast<PHINode>(User))
- UseBB = UserPN->getIncomingBlock(U);
+ V = GetValueAtEndOfBlock(UserPN->getIncomingBlock(U));
+ else
+ V = GetValueInMiddleOfBlock(User->getParent());
- U.set(GetValueInMiddleOfBlock(UseBB));
+ U.set(V);
}
// Query AvailableVals by doing an insertion of null.
std::pair<AvailableValsTy::iterator, bool> InsertRes =
- AvailableVals.insert(std::make_pair(BB, WeakVH()));
+ AvailableVals.insert(std::make_pair(BB, TrackingVH<Value>()));
// Handle the case when the insertion fails because we have already seen BB.
if (!InsertRes.second) {
// it. When we get back to the first instance of the recursion we will fill
// in the PHI node.
return InsertRes.first->second =
- PHINode::Create(PrototypeValue->getType(), PrototypeValue->getName(),
- &BB->front());
+ PHINode::Create(PrototypeValue->getType(), PrototypeValue->getName(),
+ &BB->front());
}
// Okay, the value isn't in the map and we just inserted a null in the entry
// producing the same value. If so, this value will capture it, if not, it
// will get reset to null. We distinguish the no-predecessor case explicitly
// below.
- TrackingVH<Value> SingularValue;
+ TrackingVH<Value> ExistingValue;
// We can get our predecessor info by walking the pred_iterator list, but it
// is relatively slow. If we already have PHI nodes in this block, walk one
Value *PredVal = GetValueAtEndOfBlockInternal(PredBB);
IncomingPredInfo.push_back(std::make_pair(PredBB, PredVal));
- // Compute SingularValue.
+ // Set ExistingValue to singular value from all predecessors so far.
if (i == 0)
- SingularValue = PredVal;
- else if (PredVal != SingularValue)
- SingularValue = 0;
+ ExistingValue = PredVal;
+ else if (PredVal != ExistingValue)
+ ExistingValue = 0;
}
} else {
bool isFirstPred = true;
Value *PredVal = GetValueAtEndOfBlockInternal(PredBB);
IncomingPredInfo.push_back(std::make_pair(PredBB, PredVal));
- // Compute SingularValue.
+ // Set ExistingValue to singular value from all predecessors so far.
if (isFirstPred) {
- SingularValue = PredVal;
+ ExistingValue = PredVal;
isFirstPred = false;
- } else if (PredVal != SingularValue)
- SingularValue = 0;
+ } else if (PredVal != ExistingValue)
+ ExistingValue = 0;
}
}
/// above.
TrackingVH<Value> &InsertedVal = AvailableVals[BB];
- // If all the predecessor values are the same then we don't need to insert a
+ // If the predecessor values are not all the same, then check to see if there
+ // is an existing PHI that can be used.
+ if (!ExistingValue)
+ ExistingValue = GetExistingPHI(BB,
+ IncomingPredInfo.begin()+FirstPredInfoEntry,
+ IncomingPredInfo.end());
+
+ // If there is an existing value we can use, then we don't need to insert a
// PHI. This is the simple and common case.
- if (SingularValue) {
- // If a PHI node got inserted, replace it with the singlar value and delete
+ if (ExistingValue) {
+ // If a PHI node got inserted, replace it with the existing value and delete
// it.
if (InsertedVal) {
PHINode *OldVal = cast<PHINode>(InsertedVal);
// Be careful about dead loops. These RAUW's also update InsertedVal.
- if (InsertedVal != SingularValue)
- OldVal->replaceAllUsesWith(SingularValue);
+ if (InsertedVal != ExistingValue)
+ OldVal->replaceAllUsesWith(ExistingValue);
else
OldVal->replaceAllUsesWith(UndefValue::get(InsertedVal->getType()));
OldVal->eraseFromParent();
} else {
- InsertedVal = SingularValue;
+ InsertedVal = ExistingValue;
}
+ // Either path through the 'if' should have set InsertedVal -> ExistingVal.
+ assert((InsertedVal == ExistingValue || isa<UndefValue>(InsertedVal)) &&
+ "RAUW didn't change InsertedVal to be ExistingValue");
+
// Drop the entries we added in IncomingPredInfo to restore the stack.
IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
IncomingPredInfo.end());
- return InsertedVal;
+ return ExistingValue;
}
// Otherwise, we do need a PHI: insert one now if we don't already have one.
InsertedPHI->eraseFromParent();
InsertedVal = ConstVal;
} else {
- DEBUG(errs() << " Inserted PHI: " << *InsertedPHI << "\n");
+ DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
// If the client wants to know about all new instructions, tell it.
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
projects / oota-llvm.git / blobdiff