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[objc-arc] Track if we encountered an additive overflow while computing {TopDown,BottomUp}PathCounts and do nothing if it occurred.
I fixed the aforementioned problems that came up on some of the linux boxes. Major thanks to Nick Lewycky for his help debugging! rdar://14590914 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188122 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -674,7 +674,9 @@ namespace {
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SmallVector<BasicBlock *, 2> Succs;
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public:
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BBState() : TopDownPathCount(0), BottomUpPathCount(0) {}
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static const unsigned OverflowOccurredValue;
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BBState() : TopDownPathCount(0), BottomUpPathCount(0) { }
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typedef MapTy::iterator ptr_iterator;
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typedef MapTy::const_iterator ptr_const_iterator;
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@ -745,13 +747,15 @@ namespace {
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/// Returns true if overflow occured. Returns false if overflow did not
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/// occur.
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bool GetAllPathCountWithOverflow(unsigned &PathCount) const {
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assert(TopDownPathCount != 0);
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assert(BottomUpPathCount != 0);
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if (TopDownPathCount == OverflowOccurredValue ||
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BottomUpPathCount == OverflowOccurredValue)
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return true;
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unsigned long long Product =
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(unsigned long long)TopDownPathCount*BottomUpPathCount;
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PathCount = Product;
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// Overflow occured if any of the upper bits of Product are set.
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return Product >> 32;
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// Overflow occured if any of the upper bits of Product are set or if all
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// the lower bits of Product are all set.
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return (Product >> 32) ||
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((PathCount = Product) == OverflowOccurredValue);
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}
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// Specialized CFG utilities.
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@ -766,6 +770,8 @@ namespace {
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bool isExit() const { return Succs.empty(); }
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};
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const unsigned BBState::OverflowOccurredValue = 0xffffffff;
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}
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void BBState::InitFromPred(const BBState &Other) {
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@ -781,13 +787,25 @@ void BBState::InitFromSucc(const BBState &Other) {
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/// The top-down traversal uses this to merge information about predecessors to
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/// form the initial state for a new block.
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void BBState::MergePred(const BBState &Other) {
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if (TopDownPathCount == OverflowOccurredValue)
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return;
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// Other.TopDownPathCount can be 0, in which case it is either dead or a
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// loop backedge. Loop backedges are special.
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TopDownPathCount += Other.TopDownPathCount;
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// In order to be consistent, we clear the top down pointers when by adding
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// TopDownPathCount becomes OverflowOccurredValue even though "true" overflow
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// has not occured.
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if (TopDownPathCount == OverflowOccurredValue) {
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clearTopDownPointers();
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return;
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}
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// Check for overflow. If we have overflow, fall back to conservative
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// behavior.
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if (TopDownPathCount < Other.TopDownPathCount) {
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TopDownPathCount = OverflowOccurredValue;
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clearTopDownPointers();
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return;
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}
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@ -813,13 +831,25 @@ void BBState::MergePred(const BBState &Other) {
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/// The bottom-up traversal uses this to merge information about successors to
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/// form the initial state for a new block.
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void BBState::MergeSucc(const BBState &Other) {
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if (BottomUpPathCount == OverflowOccurredValue)
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return;
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// Other.BottomUpPathCount can be 0, in which case it is either dead or a
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// loop backedge. Loop backedges are special.
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BottomUpPathCount += Other.BottomUpPathCount;
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// In order to be consistent, we clear the top down pointers when by adding
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// BottomUpPathCount becomes OverflowOccurredValue even though "true" overflow
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// has not occured.
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if (BottomUpPathCount == OverflowOccurredValue) {
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clearBottomUpPointers();
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return;
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}
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// Check for overflow. If we have overflow, fall back to conservative
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// behavior.
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if (BottomUpPathCount < Other.BottomUpPathCount) {
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BottomUpPathCount = OverflowOccurredValue;
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clearBottomUpPointers();
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return;
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}
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@ -2526,9 +2556,12 @@ ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
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// If we overflow when we compute the path count, don't remove/move
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// anything.
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const BBState &NRRBBState = BBStates[NewRetainRelease->getParent()];
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unsigned PathCount;
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unsigned PathCount = BBState::OverflowOccurredValue;
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if (NRRBBState.GetAllPathCountWithOverflow(PathCount))
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return false;
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assert(PathCount != BBState::OverflowOccurredValue &&
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"PathCount at this point can not be "
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"OverflowOccurredValue.");
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OldDelta -= PathCount;
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// Merge the ReleaseMetadata and IsTailCallRelease values.
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@ -2558,8 +2591,12 @@ ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
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// If we overflow when we compute the path count, don't
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// remove/move anything.
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const BBState &RIPBBState = BBStates[RIP->getParent()];
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PathCount = BBState::OverflowOccurredValue;
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if (RIPBBState.GetAllPathCountWithOverflow(PathCount))
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return false;
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assert(PathCount != BBState::OverflowOccurredValue &&
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"PathCount at this point can not be "
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"OverflowOccurredValue.");
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NewDelta -= PathCount;
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}
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}
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@ -2595,9 +2632,12 @@ ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
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// If we overflow when we compute the path count, don't remove/move
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// anything.
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const BBState &NRRBBState = BBStates[NewReleaseRetain->getParent()];
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unsigned PathCount;
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unsigned PathCount = BBState::OverflowOccurredValue;
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if (NRRBBState.GetAllPathCountWithOverflow(PathCount))
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return false;
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assert(PathCount != BBState::OverflowOccurredValue &&
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"PathCount at this point can not be "
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"OverflowOccurredValue.");
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OldDelta += PathCount;
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OldCount += PathCount;
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@ -2612,8 +2652,13 @@ ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
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// If we overflow when we compute the path count, don't
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// remove/move anything.
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const BBState &RIPBBState = BBStates[RIP->getParent()];
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PathCount = BBState::OverflowOccurredValue;
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if (RIPBBState.GetAllPathCountWithOverflow(PathCount))
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return false;
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assert(PathCount != BBState::OverflowOccurredValue &&
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"PathCount at this point can not be "
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"OverflowOccurredValue.");
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NewDelta += PathCount;
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NewCount += PathCount;
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}
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