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fix PR6414, a nondeterminism issue in IPSCCP which was because
of a subtle interation in a loop operating in densemap order. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97288 91177308-0d34-0410-b5e6-96231b3b80d8
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@@ -1918,6 +1918,14 @@ bool IPSCCP::runOnModule(Module &M) {
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// all call uses with the inferred value. This means we don't need to bother
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// actually returning anything from the function. Replace all return
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// instructions with return undef.
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//
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// Do this in two stages: first identify the functions we should process, then
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// actually zap their returns. This is important because we can only do this
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// the address of the function isn't taken. In cases where a return is the
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// last use of a function, the order of processing functions would affect
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// whether we other functions are optimizable.
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SmallVector<ReturnInst*, 8> ReturnsToZap;
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// TODO: Process multiple value ret instructions also.
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const DenseMap<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
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for (DenseMap<Function*, LatticeVal>::const_iterator I = RV.begin(),
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@@ -1933,7 +1941,13 @@ bool IPSCCP::runOnModule(Module &M) {
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for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
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if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
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if (!isa<UndefValue>(RI->getOperand(0)))
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RI->setOperand(0, UndefValue::get(F->getReturnType()));
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ReturnsToZap.push_back(RI);
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}
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// Zap all returns which we've identified as zap to change.
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for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
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Function *F = ReturnsToZap[i]->getParent()->getParent();
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ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
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}
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// If we infered constant or undef values for globals variables, we can delete
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