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
This commit is contained in:
Chris Lattner
2010-02-27 00:07:42 +00:00
parent e9fd444dcd
commit d38cdb020e
2 changed files with 47 additions and 1 deletions

View File

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