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[objc-arc] Track if we encountered an additive overflow while computing {TopDown,BottomUp}PathCounts and do nothing if it occured.
rdar://14590914 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187941 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -648,6 +648,8 @@ PtrState::Merge(const PtrState &Other, bool TopDown) {
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namespace {
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/// \brief Per-BasicBlock state.
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class BBState {
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static const unsigned OverflowOccurredValue;
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/// The number of unique control paths from the entry which can reach this
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/// block.
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unsigned TopDownPathCount;
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@ -674,7 +676,7 @@ 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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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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@ -745,8 +747,9 @@ 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 false;
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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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@ -766,6 +769,8 @@ namespace {
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bool isExit() const { return Succs.empty(); }
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};
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const unsigned BBState::OverflowOccurredValue = -1;
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}
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void BBState::InitFromPred(const BBState &Other) {
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@ -781,13 +786,25 @@ 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 +830,25 @@ 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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