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Indvars needs to explicitly notify ScalarEvolution when it is replacing
a loop exit value, so that if a loop gets deleted, ScalarEvolution isn't stick holding on to dangling SCEVAddRecExprs for that loop. This fixes PR6339. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96626 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -586,6 +586,11 @@ namespace llvm {
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/// compute a trip count, or if the loop is deleted.
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void forgetLoop(const Loop *L);
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/// forgetValue - This method should be called by the client when it has
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/// changed a value in a way that may effect its value, or which may
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/// disconnect it from a def-use chain linking it to a loop.
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void forgetValue(Value *V);
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/// GetMinTrailingZeros - Determine the minimum number of zero bits that S
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/// is guaranteed to end in (at every loop iteration). It is, at the same
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/// time, the minimum number of times S is divisible by 2. For example,
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@ -3485,6 +3485,35 @@ void ScalarEvolution::forgetLoop(const Loop *L) {
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}
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}
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/// forgetValue - This method should be called by the client when it has
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/// changed a value in a way that may effect its value, or which may
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/// disconnect it from a def-use chain linking it to a loop.
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void ScalarEvolution::forgetValue(Value *V) {
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I) return;
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// Drop information about expressions based on loop-header PHIs.
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SmallVector<Instruction *, 16> Worklist;
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Worklist.push_back(I);
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SmallPtrSet<Instruction *, 8> Visited;
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while (!Worklist.empty()) {
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I = Worklist.pop_back_val();
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if (!Visited.insert(I)) continue;
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std::map<SCEVCallbackVH, const SCEV *>::iterator It =
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Scalars.find(static_cast<Value *>(I));
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if (It != Scalars.end()) {
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ValuesAtScopes.erase(It->second);
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Scalars.erase(It);
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if (PHINode *PN = dyn_cast<PHINode>(I))
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ConstantEvolutionLoopExitValue.erase(PN);
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}
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PushDefUseChildren(I, Worklist);
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}
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}
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/// ComputeBackedgeTakenCount - Compute the number of times the backedge
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/// of the specified loop will execute.
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ScalarEvolution::BackedgeTakenInfo
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@ -246,6 +246,13 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L,
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if (!PN->getType()->isIntegerTy() && !PN->getType()->isPointerTy())
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continue;
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// It's necessary to tell ScalarEvolution about this explicitly so that
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// it can walk the def-use list and forget all SCEVs, as it may not be
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// watching the PHI itself. Once the new exit value is in place, there
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// may not be a def-use connection between the loop and every instruction
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// which got a SCEVAddRecExpr for that loop.
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SE->forgetValue(PN);
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// Iterate over all of the values in all the PHI nodes.
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for (unsigned i = 0; i != NumPreds; ++i) {
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// If the value being merged in is not integer or is not defined
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