[llvm-commits] [llvm] r100264 - in /llvm/trunk: include/llvm/Transforms/Utils/SSAUpdater.h lib/Transforms/Utils/SSAUpdater.cpp test/Transforms/GVN/2010-03-31-RedundantPHIs.ll
Bob Wilson
bob.wilson at apple.com
Fri Apr 2 20:50:38 PDT 2010
Author: bwilson
Date: Fri Apr 2 22:50:38 2010
New Revision: 100264
URL: http://llvm.org/viewvc/llvm-project?rev=100264&view=rev
Log:
Revert all my SSAUpdater patches. The PHI placement algorithm is not correct
(what was I thinking?) and there's also a problem with LCSSA. I'll try again
later with fixes.
--- Reverse-merging r100263 into '.':
U lib/Transforms/Utils/SSAUpdater.cpp
--- Reverse-merging r100177 into '.':
G lib/Transforms/Utils/SSAUpdater.cpp
--- Reverse-merging r100148 into '.':
G lib/Transforms/Utils/SSAUpdater.cpp
--- Reverse-merging r100147 into '.':
U include/llvm/Transforms/Utils/SSAUpdater.h
G lib/Transforms/Utils/SSAUpdater.cpp
--- Reverse-merging r100131 into '.':
G include/llvm/Transforms/Utils/SSAUpdater.h
G lib/Transforms/Utils/SSAUpdater.cpp
--- Reverse-merging r100130 into '.':
G lib/Transforms/Utils/SSAUpdater.cpp
--- Reverse-merging r100126 into '.':
G include/llvm/Transforms/Utils/SSAUpdater.h
G lib/Transforms/Utils/SSAUpdater.cpp
--- Reverse-merging r100050 into '.':
D test/Transforms/GVN/2010-03-31-RedundantPHIs.ll
--- Reverse-merging r100047 into '.':
G include/llvm/Transforms/Utils/SSAUpdater.h
G lib/Transforms/Utils/SSAUpdater.cpp
Removed:
llvm/trunk/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll
Modified:
llvm/trunk/include/llvm/Transforms/Utils/SSAUpdater.h
llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp
Modified: llvm/trunk/include/llvm/Transforms/Utils/SSAUpdater.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/SSAUpdater.h?rev=100264&r1=100263&r2=100264&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/SSAUpdater.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/SSAUpdater.h Fri Apr 2 22:50:38 2010
@@ -27,28 +27,22 @@
/// transformation wants to rewrite a set of uses of one value with uses of a
/// set of values.
class SSAUpdater {
-public:
- class BBInfo;
-
-private:
/// AvailableVals - This keeps track of which value to use on a per-block
- /// basis. When we insert PHI nodes, we keep track of them here.
- //typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
+ /// basis. When we insert PHI nodes, we keep track of them here. We use
+ /// TrackingVH's for the value of the map because we RAUW PHI nodes when we
+ /// eliminate them, and want the TrackingVH's to track this.
+ //typedef DenseMap<BasicBlock*, TrackingVH<Value> > AvailableValsTy;
void *AV;
/// PrototypeValue is an arbitrary representative value, which we derive names
/// and a type for PHI nodes.
Value *PrototypeValue;
- /// BBMap - The GetValueAtEndOfBlock method maintains this mapping from
- /// basic blocks to BBInfo structures.
- /// typedef DenseMap<BasicBlock*, BBInfo*> BBMapTy;
- void *BM;
-
- /// Allocator - The GetValueAtEndOfBlock method uses this BumpPtrAllocator to
- /// hold its internal data. The allocator and its storage is created and
- /// discarded for each invocation of GetValueAtEndOfBlock.
- void *BPA;
+ /// IncomingPredInfo - We use this as scratch space when doing our recursive
+ /// walk. This should only be used in GetValueInBlockInternal, normally it
+ /// should be empty.
+ //std::vector<std::pair<BasicBlock*, TrackingVH<Value> > > IncomingPredInfo;
+ void *IPI;
/// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
/// it creates to the vector.
@@ -105,14 +99,6 @@
private:
Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
- void FindPHIPlacement(BasicBlock *BB, BBInfo *Info, bool &Changed,
- unsigned Counter);
- void FindAvailableVal(BasicBlock *BB, BBInfo *Info, unsigned Counter);
- void FindExistingPHI(BasicBlock *BB);
- bool CheckIfPHIMatches(PHINode *PHI);
- void RecordMatchingPHI(PHINode *PHI);
- void ClearPHITags(PHINode *PHI);
-
void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
};
Modified: llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp?rev=100264&r1=100263&r2=100264&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp Fri Apr 2 22:50:38 2010
@@ -11,86 +11,34 @@
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "ssaupdater"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Instructions.h"
#include "llvm/ADT/DenseMap.h"
-#include "llvm/Support/AlignOf.h"
-#include "llvm/Support/Allocator.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
-/// BBInfo - Per-basic block information used internally by SSAUpdater.
-/// The predecessors of each block are cached here since pred_iterator is
-/// slow and we need to iterate over the blocks at least a few times.
-class SSAUpdater::BBInfo {
-public:
- Value *AvailableVal; // Value to use in this block.
- BasicBlock *DefBB; // Block that defines the available value.
- unsigned NumPreds; // Number of predecessor blocks.
- BasicBlock **Preds; // Array[NumPreds] of predecessor blocks.
- unsigned Counter; // Marker to identify blocks already visited.
- PHINode *PHITag; // Marker for existing PHIs that match.
-
- BBInfo(BasicBlock *BB, Value *V, BumpPtrAllocator *Allocator);
-};
-typedef DenseMap<BasicBlock*, SSAUpdater::BBInfo*> BBMapTy;
-
-SSAUpdater::BBInfo::BBInfo(BasicBlock *BB, Value *V,
- BumpPtrAllocator *Allocator)
- : AvailableVal(V), DefBB(0), NumPreds(0), Preds(0), Counter(0), PHITag(0) {
- // If this block has a known value, don't bother finding its predecessors.
- if (V) {
- DefBB = BB;
- return;
- }
-
- // 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
- // of them to get the predecessor list instead.
- if (PHINode *SomePhi = dyn_cast<PHINode>(BB->begin())) {
- NumPreds = SomePhi->getNumIncomingValues();
- Preds = static_cast<BasicBlock**>
- (Allocator->Allocate(NumPreds * sizeof(BasicBlock*),
- AlignOf<BasicBlock*>::Alignment));
- for (unsigned pi = 0; pi != NumPreds; ++pi)
- Preds[pi] = SomePhi->getIncomingBlock(pi);
- return;
- }
-
- // Stash the predecessors in a temporary vector until we know how much space
- // to allocate for them.
- SmallVector<BasicBlock*, 10> TmpPreds;
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
- TmpPreds.push_back(*PI);
- ++NumPreds;
- }
- Preds = static_cast<BasicBlock**>
- (Allocator->Allocate(NumPreds * sizeof(BasicBlock*),
- AlignOf<BasicBlock*>::Alignment));
- memcpy(Preds, TmpPreds.data(), NumPreds * sizeof(BasicBlock*));
-}
+typedef DenseMap<BasicBlock*, TrackingVH<Value> > AvailableValsTy;
+typedef std::vector<std::pair<BasicBlock*, TrackingVH<Value> > >
+ IncomingPredInfoTy;
-typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
static AvailableValsTy &getAvailableVals(void *AV) {
return *static_cast<AvailableValsTy*>(AV);
}
-static BBMapTy *getBBMap(void *BM) {
- return static_cast<BBMapTy*>(BM);
+static IncomingPredInfoTy &getIncomingPredInfo(void *IPI) {
+ return *static_cast<IncomingPredInfoTy*>(IPI);
}
-static BumpPtrAllocator *getAllocator(void *BPA) {
- return static_cast<BumpPtrAllocator*>(BPA);
-}
SSAUpdater::SSAUpdater(SmallVectorImpl<PHINode*> *NewPHI)
- : AV(0), PrototypeValue(0), BM(0), BPA(0), InsertedPHIs(NewPHI) {}
+ : AV(0), PrototypeValue(0), IPI(0), InsertedPHIs(NewPHI) {}
SSAUpdater::~SSAUpdater() {
delete &getAvailableVals(AV);
+ delete &getIncomingPredInfo(IPI);
}
/// Initialize - Reset this object to get ready for a new set of SSA
@@ -100,6 +48,11 @@
AV = new AvailableValsTy();
else
getAvailableVals(AV).clear();
+
+ if (IPI == 0)
+ IPI = new IncomingPredInfoTy();
+ else
+ getIncomingPredInfo(IPI).clear();
PrototypeValue = ProtoValue;
}
@@ -120,7 +73,7 @@
/// IsEquivalentPHI - Check if PHI has the same incoming value as specified
/// in ValueMapping for each predecessor block.
-static bool IsEquivalentPHI(PHINode *PHI,
+static bool IsEquivalentPHI(PHINode *PHI,
DenseMap<BasicBlock*, Value*> &ValueMapping) {
unsigned PHINumValues = PHI->getNumIncomingValues();
if (PHINumValues != ValueMapping.size())
@@ -136,12 +89,38 @@
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) {
- assert(BM == 0 && BPA == 0 && "Unexpected Internal State");
+ assert(getIncomingPredInfo(IPI).empty() && "Unexpected Internal State");
Value *Res = GetValueAtEndOfBlockInternal(BB);
- assert(BM == 0 && BPA == 0 && "Unexpected Internal State");
+ assert(getIncomingPredInfo(IPI).empty() && "Unexpected Internal State");
return Res;
}
@@ -167,7 +146,7 @@
Value *SSAUpdater::GetValueInMiddleOfBlock(BasicBlock *BB) {
// If there is no definition of the renamed variable in this block, just use
// GetValueAtEndOfBlock to do our work.
- if (!HasValueForBlock(BB))
+ if (!getAvailableVals(AV).count(BB))
return GetValueAtEndOfBlock(BB);
// Otherwise, we have the hard case. Get the live-in values for each
@@ -214,18 +193,10 @@
if (SingularValue != 0)
return SingularValue;
- // Otherwise, we do need a PHI: check to see if we already have one available
- // in this block that produces the right value.
- if (isa<PHINode>(BB->begin())) {
- DenseMap<BasicBlock*, Value*> ValueMapping(PredValues.begin(),
- PredValues.end());
- PHINode *SomePHI;
- for (BasicBlock::iterator It = BB->begin();
- (SomePHI = dyn_cast<PHINode>(It)); ++It) {
- if (IsEquivalentPHI(SomePHI, ValueMapping))
- return SomePHI;
- }
- }
+ // 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(),
@@ -255,7 +226,7 @@
/// which use their value in the corresponding predecessor.
void SSAUpdater::RewriteUse(Use &U) {
Instruction *User = cast<Instruction>(U.getUser());
-
+
Value *V;
if (PHINode *UserPN = dyn_cast<PHINode>(User))
V = GetValueAtEndOfBlock(UserPN->getIncomingBlock(U));
@@ -265,264 +236,161 @@
U.set(V);
}
+
/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry
/// for the specified BB and if so, return it. If not, construct SSA form by
-/// first calculating the required placement of PHIs and then inserting new
-/// PHIs where needed.
+/// walking predecessors inserting PHI nodes as needed until we get to a block
+/// where the value is available.
+///
Value *SSAUpdater::GetValueAtEndOfBlockInternal(BasicBlock *BB) {
AvailableValsTy &AvailableVals = getAvailableVals(AV);
- if (Value *V = AvailableVals[BB])
- return V;
-
- // Pool allocation used internally by GetValueAtEndOfBlock.
- BumpPtrAllocator AllocatorObj;
- BBMapTy BBMapObj;
- BPA = &AllocatorObj;
- BM = &BBMapObj;
-
- BBInfo *Info = new (AllocatorObj) BBInfo(BB, 0, &AllocatorObj);
- BBMapObj[BB] = Info;
-
- bool Changed;
- unsigned Counter = 1;
- do {
- Changed = false;
- FindPHIPlacement(BB, Info, Changed, Counter);
- ++Counter;
- } while (Changed);
-
- FindAvailableVal(BB, Info, Counter);
-
- BPA = 0;
- BM = 0;
- return Info->AvailableVal;
-}
-
-/// FindPHIPlacement - Recursively visit the predecessors of a block to find
-/// the reaching definition for each predecessor and then determine whether
-/// a PHI is needed in this block.
-void SSAUpdater::FindPHIPlacement(BasicBlock *BB, BBInfo *Info, bool &Changed,
- unsigned Counter) {
- AvailableValsTy &AvailableVals = getAvailableVals(AV);
- BBMapTy *BBMap = getBBMap(BM);
- BumpPtrAllocator *Allocator = getAllocator(BPA);
- bool BBNeedsPHI = false;
- BasicBlock *SamePredDefBB = 0;
-
- // If there are no predecessors, then we must have found an unreachable
- // block. Treat it as a definition with 'undef'.
- if (Info->NumPreds == 0) {
- Info->AvailableVal = UndefValue::get(PrototypeValue->getType());
- Info->DefBB = BB;
- return;
- }
-
- Info->Counter = Counter;
- for (unsigned pi = 0; pi != Info->NumPreds; ++pi) {
- BasicBlock *Pred = Info->Preds[pi];
- BBMapTy::value_type &BBMapBucket = BBMap->FindAndConstruct(Pred);
- if (!BBMapBucket.second) {
- Value *PredVal = AvailableVals.lookup(Pred);
- BBMapBucket.second = new (*Allocator) BBInfo(Pred, PredVal, Allocator);
- }
- BBInfo *PredInfo = BBMapBucket.second;
- BasicBlock *DefBB = 0;
- if (!PredInfo->AvailableVal) {
- if (PredInfo->Counter != Counter)
- FindPHIPlacement(Pred, PredInfo, Changed, Counter);
-
- // Ignore back edges where the value is not yet known.
- if (!PredInfo->DefBB)
- continue;
- }
- DefBB = PredInfo->DefBB;
-
- if (!SamePredDefBB)
- SamePredDefBB = DefBB;
- else if (DefBB != SamePredDefBB)
- BBNeedsPHI = true;
- }
-
- BasicBlock *NewDefBB = (BBNeedsPHI ? BB : SamePredDefBB);
- if (Info->DefBB != NewDefBB) {
- Changed = true;
- Info->DefBB = NewDefBB;
- }
-}
-/// FindAvailableVal - If this block requires a PHI, first check if an existing
-/// PHI matches the PHI placement and reaching definitions computed earlier,
-/// and if not, create a new PHI. Visit all the block's predecessors to
-/// calculate the available value for each one and fill in the incoming values
-/// for a new PHI.
-void SSAUpdater::FindAvailableVal(BasicBlock *BB, BBInfo *Info,
- unsigned Counter) {
- if (Info->AvailableVal || Info->Counter == Counter)
- return;
+ // Query AvailableVals by doing an insertion of null.
+ std::pair<AvailableValsTy::iterator, bool> InsertRes =
+ AvailableVals.insert(std::make_pair(BB, TrackingVH<Value>()));
+
+ // Handle the case when the insertion fails because we have already seen BB.
+ if (!InsertRes.second) {
+ // If the insertion failed, there are two cases. The first case is that the
+ // value is already available for the specified block. If we get this, just
+ // return the value.
+ if (InsertRes.first->second != 0)
+ return InsertRes.first->second;
+
+ // Otherwise, if the value we find is null, then this is the value is not
+ // known but it is being computed elsewhere in our recursion. This means
+ // that we have a cycle. Handle this by inserting a PHI node and returning
+ // 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());
+ }
+
+ // Okay, the value isn't in the map and we just inserted a null in the entry
+ // to indicate that we're processing the block. Since we have no idea what
+ // value is in this block, we have to recurse through our predecessors.
+ //
+ // While we're walking our predecessors, we keep track of them in a vector,
+ // then insert a PHI node in the end if we actually need one. We could use a
+ // smallvector here, but that would take a lot of stack space for every level
+ // of the recursion, just use IncomingPredInfo as an explicit stack.
+ IncomingPredInfoTy &IncomingPredInfo = getIncomingPredInfo(IPI);
+ unsigned FirstPredInfoEntry = IncomingPredInfo.size();
+
+ // As we're walking the predecessors, keep track of whether they are all
+ // 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> ExistingValue;
- AvailableValsTy &AvailableVals = getAvailableVals(AV);
- BBMapTy *BBMap = getBBMap(BM);
+ // 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
+ // of them to get the predecessor list instead.
+ if (PHINode *SomePhi = dyn_cast<PHINode>(BB->begin())) {
+ for (unsigned i = 0, e = SomePhi->getNumIncomingValues(); i != e; ++i) {
+ BasicBlock *PredBB = SomePhi->getIncomingBlock(i);
+ Value *PredVal = GetValueAtEndOfBlockInternal(PredBB);
+ IncomingPredInfo.push_back(std::make_pair(PredBB, PredVal));
- // Check if there needs to be a PHI in BB.
- PHINode *NewPHI = 0;
- if (Info->DefBB == BB) {
- // Look for an existing PHI.
- FindExistingPHI(BB);
- if (!Info->AvailableVal) {
- NewPHI = PHINode::Create(PrototypeValue->getType(),
- PrototypeValue->getName(), &BB->front());
- NewPHI->reserveOperandSpace(Info->NumPreds);
- Info->AvailableVal = NewPHI;
- AvailableVals[BB] = NewPHI;
+ // Set ExistingValue to singular value from all predecessors so far.
+ if (i == 0)
+ ExistingValue = PredVal;
+ else if (PredVal != ExistingValue)
+ ExistingValue = 0;
}
- }
-
- // Iterate through the block's predecessors.
- Info->Counter = Counter;
- for (unsigned pi = 0; pi != Info->NumPreds; ++pi) {
- BasicBlock *Pred = Info->Preds[pi];
- BBInfo *PredInfo = (*BBMap)[Pred];
- FindAvailableVal(Pred, PredInfo, Counter);
- if (NewPHI) {
- // Skip to the nearest preceding definition.
- if (PredInfo->DefBB != Pred)
- PredInfo = (*BBMap)[PredInfo->DefBB];
- NewPHI->addIncoming(PredInfo->AvailableVal, Pred);
- } else if (!Info->AvailableVal)
- Info->AvailableVal = PredInfo->AvailableVal;
- }
-
- if (NewPHI) {
- DEBUG(dbgs() << " Inserted PHI: " << *NewPHI << "\n");
-
- // If the client wants to know about all new instructions, tell it.
- if (InsertedPHIs) InsertedPHIs->push_back(NewPHI);
- }
-}
+ } else {
+ bool isFirstPred = true;
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ BasicBlock *PredBB = *PI;
+ Value *PredVal = GetValueAtEndOfBlockInternal(PredBB);
+ IncomingPredInfo.push_back(std::make_pair(PredBB, PredVal));
-/// FindExistingPHI - Look through the PHI nodes in a block to see if any of
-/// them match what is needed.
-void SSAUpdater::FindExistingPHI(BasicBlock *BB) {
- PHINode *SomePHI;
- for (BasicBlock::iterator It = BB->begin();
- (SomePHI = dyn_cast<PHINode>(It)); ++It) {
- if (CheckIfPHIMatches(SomePHI)) {
- RecordMatchingPHI(SomePHI);
- break;
+ // Set ExistingValue to singular value from all predecessors so far.
+ if (isFirstPred) {
+ ExistingValue = PredVal;
+ isFirstPred = false;
+ } else if (PredVal != ExistingValue)
+ ExistingValue = 0;
}
- ClearPHITags(SomePHI);
}
-}
-/// CheckIfPHIMatches - Check if a PHI node matches the placement and values
-/// in the BBMap.
-bool SSAUpdater::CheckIfPHIMatches(PHINode *PHI) {
- BBMapTy *BBMap = getBBMap(BM);
- SmallVector<PHINode*, 20> WorkList;
- WorkList.push_back(PHI);
-
- // Mark that the block containing this PHI has been visited.
- (*BBMap)[PHI->getParent()]->PHITag = PHI;
-
- while (!WorkList.empty()) {
- PHI = WorkList.pop_back_val();
-
- // Iterate through the PHI's incoming values.
- for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
- Value *IncomingVal = PHI->getIncomingValue(i);
- BasicBlock *Pred = PHI->getIncomingBlock(i);
- BBInfo *PredInfo = (*BBMap)[Pred];
- // Skip to the nearest preceding definition.
- if (PredInfo->DefBB != Pred) {
- Pred = PredInfo->DefBB;
- PredInfo = (*BBMap)[Pred];
- }
-
- // Check if it matches the expected value.
- if (PredInfo->AvailableVal) {
- if (IncomingVal == PredInfo->AvailableVal)
- continue;
- return false;
- }
-
- // Check if the value is a PHI in the correct block.
- PHINode *IncomingPHIVal = dyn_cast<PHINode>(IncomingVal);
- if (!IncomingPHIVal || IncomingPHIVal->getParent() != Pred)
- return false;
-
- // If this block has already been visited, check if this PHI matches.
- if (PredInfo->PHITag) {
- if (IncomingPHIVal == PredInfo->PHITag)
- continue;
- return false;
- }
- PredInfo->PHITag = IncomingPHIVal;
+ // If there are no predecessors, then we must have found an unreachable block
+ // just return 'undef'. Since there are no predecessors, InsertRes must not
+ // be invalidated.
+ if (IncomingPredInfo.size() == FirstPredInfoEntry)
+ return InsertRes.first->second = UndefValue::get(PrototypeValue->getType());
+
+ /// Look up BB's entry in AvailableVals. 'InsertRes' may be invalidated. If
+ /// this block is involved in a loop, a no-entry PHI node will have been
+ /// inserted as InsertedVal. Otherwise, we'll still have the null we inserted
+ /// above.
+ TrackingVH<Value> &InsertedVal = AvailableVals[BB];
+
+ // 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 (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 != ExistingValue)
+ OldVal->replaceAllUsesWith(ExistingValue);
+ else
+ OldVal->replaceAllUsesWith(UndefValue::get(InsertedVal->getType()));
+ OldVal->eraseFromParent();
+ } else {
+ 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 ExistingValue;
+ }
+
+ // Otherwise, we do need a PHI: insert one now if we don't already have one.
+ if (InsertedVal == 0)
+ InsertedVal = PHINode::Create(PrototypeValue->getType(),
+ PrototypeValue->getName(), &BB->front());
- WorkList.push_back(IncomingPHIVal);
- }
- }
- return true;
-}
+ PHINode *InsertedPHI = cast<PHINode>(InsertedVal);
+ InsertedPHI->reserveOperandSpace(IncomingPredInfo.size()-FirstPredInfoEntry);
-/// RecordMatchingPHI - For a PHI node that matches, record it and its input
-/// PHIs in both the BBMap and the AvailableVals mapping.
-void SSAUpdater::RecordMatchingPHI(PHINode *PHI) {
- BBMapTy *BBMap = getBBMap(BM);
- AvailableValsTy &AvailableVals = getAvailableVals(AV);
- SmallVector<PHINode*, 20> WorkList;
- WorkList.push_back(PHI);
+ // Fill in all the predecessors of the PHI.
+ for (IncomingPredInfoTy::iterator I =
+ IncomingPredInfo.begin()+FirstPredInfoEntry,
+ E = IncomingPredInfo.end(); I != E; ++I)
+ InsertedPHI->addIncoming(I->second, I->first);
+
+ // Drop the entries we added in IncomingPredInfo to restore the stack.
+ IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
+ IncomingPredInfo.end());
- // Record this PHI.
- BasicBlock *BB = PHI->getParent();
- AvailableVals[BB] = PHI;
- (*BBMap)[BB]->AvailableVal = PHI;
-
- while (!WorkList.empty()) {
- PHI = WorkList.pop_back_val();
-
- // Iterate through the PHI's incoming values.
- for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
- PHINode *IncomingPHIVal = dyn_cast<PHINode>(PHI->getIncomingValue(i));
- if (!IncomingPHIVal) continue;
- BB = IncomingPHIVal->getParent();
- BBInfo *Info = (*BBMap)[BB];
- if (!Info || Info->AvailableVal)
- continue;
-
- // Record the PHI and add it to the worklist.
- AvailableVals[BB] = IncomingPHIVal;
- Info->AvailableVal = IncomingPHIVal;
- WorkList.push_back(IncomingPHIVal);
- }
- }
-}
+ // See if the PHI node can be merged to a single value. This can happen in
+ // loop cases when we get a PHI of itself and one other value.
+ if (Value *ConstVal = InsertedPHI->hasConstantValue()) {
+ InsertedPHI->replaceAllUsesWith(ConstVal);
+ InsertedPHI->eraseFromParent();
+ InsertedVal = ConstVal;
+ } else {
+ DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
-/// ClearPHITags - When one of the existing PHI nodes fails to match, clear
-/// the PHITag values that were stored in the BBMap when checking to see if
-/// it matched.
-void SSAUpdater::ClearPHITags(PHINode *PHI) {
- BBMapTy *BBMap = getBBMap(BM);
- SmallVector<PHINode*, 20> WorkList;
- WorkList.push_back(PHI);
-
- // Clear the tag for this PHI.
- (*BBMap)[PHI->getParent()]->PHITag = 0;
-
- while (!WorkList.empty()) {
- PHI = WorkList.pop_back_val();
-
- // Iterate through the PHI's incoming values.
- for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
- PHINode *IncomingPHIVal = dyn_cast<PHINode>(PHI->getIncomingValue(i));
- if (!IncomingPHIVal) continue;
- BasicBlock *BB = IncomingPHIVal->getParent();
- BBInfo *Info = (*BBMap)[BB];
- if (!Info || Info->AvailableVal || !Info->PHITag)
- continue;
-
- // Clear the tag and add the PHI to the worklist.
- Info->PHITag = 0;
- WorkList.push_back(IncomingPHIVal);
- }
+ // If the client wants to know about all new instructions, tell it.
+ if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
}
+
+ return InsertedVal;
}
Removed: llvm/trunk/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll?rev=100263&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll (original)
+++ llvm/trunk/test/Transforms/GVN/2010-03-31-RedundantPHIs.ll (removed)
@@ -1,46 +0,0 @@
-; RUN: opt < %s -gvn -enable-full-load-pre -S | FileCheck %s
-
-define i8* @cat(i8* %s1, ...) nounwind {
-entry:
- br i1 undef, label %bb, label %bb3
-
-bb: ; preds = %entry
- unreachable
-
-bb3: ; preds = %entry
- store i8* undef, i8** undef, align 4
- br i1 undef, label %bb5, label %bb6
-
-bb5: ; preds = %bb3
- unreachable
-
-bb6: ; preds = %bb3
- br label %bb12
-
-bb8: ; preds = %bb12
- br i1 undef, label %bb9, label %bb10
-
-bb9: ; preds = %bb8
- %0 = load i8** undef, align 4 ; <i8*> [#uses=0]
- %1 = load i8** undef, align 4 ; <i8*> [#uses=0]
- br label %bb11
-
-bb10: ; preds = %bb8
- br label %bb11
-
-bb11: ; preds = %bb10, %bb9
-; CHECK: bb11:
-; CHECK: phi
-; CHECK-NOT: phi
- br label %bb12
-
-bb12: ; preds = %bb11, %bb6
-; CHECK: bb12:
-; CHECK: phi
-; CHECK-NOT: phi
- br i1 undef, label %bb8, label %bb13
-
-bb13: ; preds = %bb12
-; CHECK: bb13:
- ret i8* undef
-}
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