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In ScalarEvolution::forgetValue, eliminate any SCEVUnknown

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entries associated with the value being erased in the
folding set map.  These entries used to be harmless, because
a SCEVUnknown doesn't store any information about its Value*,
so having a new Value allocated at the old Value's address
wasn't a problem. But now that ScalarEvolution is storing more
information about values, this is no longer safe.

llvm-svn: 107316
This commit is contained in:
Dan Gohman 2010-06-30 20:21:12 +00:00
parent 7ae1ebd3b4
commit 547c92af20
1 changed files with 20 additions and 0 deletions
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20
lib/Analysis/ScalarEvolution.cpp
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@ -3657,6 +3657,26 @@ void ScalarEvolution::forgetValue(Value *V) {
ConstantEvolutionLoopExitValue.erase(PN);
}
// If there's a SCEVUnknown tying this value into the SCEV
// space, remove it from the folding set map. The SCEVUnknown
// object and any other SCEV objects which reference it
// (transitively) remain allocated, effectively leaked until
// the underlying BumpPtrAllocator is freed.
//
// This permits SCEV pointers to be used as keys in maps
// such as the ValuesAtScopes map.
FoldingSetNodeID ID;
ID.AddInteger(scUnknown);
ID.AddPointer(I);
void *IP;
if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
UniqueSCEVs.RemoveNode(S);
// This isn't necessary, but we might as well remove the
// value from the ValuesAtScopes map too.
ValuesAtScopes.erase(S);
}
PushDefUseChildren(I, Worklist);
}
}