//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "objc-arc"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/ADT/DenseMap.h"
using namespace llvm;
// An ObjC-Identified object can't alias a load if it is never locally stored.
if (AIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(B))
+ return isStoredObjCPointer(A);
if (BIsIdentified) {
- // If both pointers have provenance, they can be directly compared.
- if (A != B)
- return false;
- } else {
- if (isa<LoadInst>(B))
- return isStoredObjCPointer(A);
+ // Check for an obvious escape.
+ if (isa<LoadInst>(A))
+ return isStoredObjCPointer(B);
+ // Both pointers are identified and escapes aren't an evident problem.
+ return false;
}
- } else {
- if (BIsIdentified && isa<LoadInst>(A))
+ } else if (BIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(A))
return isStoredObjCPointer(B);
}
/// PtrState - This class summarizes several per-pointer runtime properties
/// which are propogated through the flow graph.
class PtrState {
- /// NestCount - The known minimum level of retain+release nesting.
- unsigned NestCount;
-
/// KnownPositiveRefCount - True if the reference count is known to
/// be incremented.
bool KnownPositiveRefCount;
/// TODO: Encapsulate this better.
RRInfo RRI;
- PtrState() : NestCount(0), KnownPositiveRefCount(false), Partial(false),
+ PtrState() : KnownPositiveRefCount(false), Partial(false),
Seq(S_None) {}
void SetKnownPositiveRefCount() {
return KnownPositiveRefCount;
}
- void IncrementNestCount() {
- if (NestCount != UINT_MAX) ++NestCount;
- }
-
- void DecrementNestCount() {
- if (NestCount != 0) --NestCount;
- }
-
- bool IsKnownNested() const {
- return NestCount > 0;
- }
-
void SetSeq(Sequence NewSeq) {
Seq = NewSeq;
}
PtrState::Merge(const PtrState &Other, bool TopDown) {
Seq = MergeSeqs(Seq, Other.Seq, TopDown);
KnownPositiveRefCount = KnownPositiveRefCount && Other.KnownPositiveRefCount;
- NestCount = std::min(NestCount, Other.NestCount);
// We can't merge a plain objc_retain with an objc_retainBlock.
if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
// loop backedge. Loop backedges are special.
TopDownPathCount += Other.TopDownPathCount;
+ // Check for overflow. If we have overflow, fall back to conservative behavior.
+ if (TopDownPathCount < Other.TopDownPathCount) {
+ clearTopDownPointers();
+ return;
+ }
+
// For each entry in the other set, if our set has an entry with the same key,
// merge the entries. Otherwise, copy the entry and merge it with an empty
// entry.
// loop backedge. Loop backedges are special.
BottomUpPathCount += Other.BottomUpPathCount;
+ // Check for overflow. If we have overflow, fall back to conservative behavior.
+ if (BottomUpPathCount < Other.BottomUpPathCount) {
+ clearBottomUpPointers();
+ return;
+ }
+
// For each entry in the other set, if our set has an entry with the
// same key, merge the entries. Otherwise, copy the entry and merge
// it with an empty entry.
return AutoreleaseCallee;
}
+/// IsPotentialUse - Test whether the given value is possible a
+/// reference-counted pointer, including tests which utilize AliasAnalysis.
+static bool IsPotentialUse(const Value *Op, AliasAnalysis &AA) {
+ // First make the rudimentary check.
+ if (!IsPotentialUse(Op))
+ return false;
+
+ // Objects in constant memory are not reference-counted.
+ if (AA.pointsToConstantMemory(Op))
+ return false;
+
+ // Pointers in constant memory are not pointing to reference-counted objects.
+ if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
+ if (AA.pointsToConstantMemory(LI->getPointerOperand()))
+ return false;
+
+ // Otherwise assume the worst.
+ return true;
+}
+
/// CanAlterRefCount - Test whether the given instruction can result in a
/// reference count modification (positive or negative) for the pointer's
/// object.
for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
I != E; ++I) {
const Value *Op = *I;
- if (IsPotentialUse(Op) && PA.related(Ptr, Op))
+ if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
return true;
}
return false;
// Comparing a pointer with null, or any other constant, isn't really a use,
// because we don't care what the pointer points to, or about the values
// of any other dynamic reference-counted pointers.
- if (!IsPotentialUse(ICI->getOperand(1)))
+ if (!IsPotentialUse(ICI->getOperand(1), *PA.getAA()))
return false;
} else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
// For calls, just check the arguments (and not the callee operand).
for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
OE = CS.arg_end(); OI != OE; ++OI) {
const Value *Op = *OI;
- if (IsPotentialUse(Op) && PA.related(Ptr, Op))
+ if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
return true;
}
return false;
const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
// If we can't tell what the underlying object was, assume there is a
// dependence.
- return IsPotentialUse(Op) && PA.related(Op, Ptr);
+ return IsPotentialUse(Op, *PA.getAA()) && PA.related(Op, Ptr);
}
// Check each operand for a match.
for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
OI != OE; ++OI) {
const Value *Op = *OI;
- if (IsPotentialUse(Op) && PA.related(Ptr, Op))
+ if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
return true;
}
return false;
MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
S.ResetSequenceProgress(ReleaseMetadata ? S_MovableRelease : S_Release);
S.RRI.ReleaseMetadata = ReleaseMetadata;
- S.RRI.KnownSafe = S.IsKnownNested() || S.IsKnownIncremented();
+ S.RRI.KnownSafe = S.IsKnownIncremented();
S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
S.RRI.Calls.insert(Inst);
- S.IncrementNestCount();
+ S.SetKnownPositiveRefCount();
break;
}
case IC_RetainBlock:
PtrState &S = MyStates.getPtrBottomUpState(Arg);
S.SetKnownPositiveRefCount();
- S.DecrementNestCount();
switch (S.GetSeq()) {
case S_Stop:
// Merge the states from each successor to compute the initial state
// for the current block.
- for (BBState::edge_iterator SI(MyStates.succ_begin()),
- SE(MyStates.succ_end()); SI != SE; ++SI) {
+ BBState::edge_iterator SI(MyStates.succ_begin()),
+ SE(MyStates.succ_end());
+ if (SI != SE) {
const BasicBlock *Succ = *SI;
DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ);
assert(I != BBStates.end());
assert(I != BBStates.end());
MyStates.MergeSucc(I->second);
}
- break;
}
// Visit all the instructions, bottom-up.
S.ResetSequenceProgress(S_Retain);
S.RRI.IsRetainBlock = Class == IC_RetainBlock;
- // Don't check S.IsKnownIncremented() here because it's not sufficient.
- S.RRI.KnownSafe = S.IsKnownNested();
+ S.RRI.KnownSafe = S.IsKnownIncremented();
S.RRI.Calls.insert(Inst);
}
- S.IncrementNestCount();
+ S.SetKnownPositiveRefCount();
// A retain can be a potential use; procede to the generic checking
// code below.
Arg = GetObjCArg(Inst);
PtrState &S = MyStates.getPtrTopDownState(Arg);
- S.DecrementNestCount();
+ S.ClearRefCount();
switch (S.GetSeq()) {
case S_Retain:
// Merge the states from each predecessor to compute the initial state
// for the current block.
- for (BBState::edge_iterator PI(MyStates.pred_begin()),
- PE(MyStates.pred_end()); PI != PE; ++PI) {
+ BBState::edge_iterator PI(MyStates.pred_begin()),
+ PE(MyStates.pred_end());
+ if (PI != PE) {
const BasicBlock *Pred = *PI;
DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred);
assert(I != BBStates.end());
assert(I != BBStates.end());
MyStates.MergePred(I->second);
}
- break;
}
// Visit all the instructions, top-down.
projects / oota-llvm.git / blobdiff