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Factor out some of the code for updating old SCEVUnknown values, and

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extend it to handle the case where multiple RAUWs affect a single
SCEVUnknown.

Add a ScalarEvolution unittest to test for this situation.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109705 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-07-29 00:17:55 +00:00
parent e2fb451dbb
commit c6743207e2
6 changed files with 162 additions and 33 deletions
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5
include/llvm/Analysis/ScalarEvolution.h
View File

@@ -386,6 +386,11 @@ namespace llvm {
bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
/// forgetSCEVUnknown - V is being deleted or RAUW'd; remove the
/// SCEVUnknown for it from the uniquing map, and optionally
/// clear its contents to point to a replacement value.
void forgetSCEVUnknown(Value *V, Value *NewV);
public:
static char ID; // Pass identification, replacement for typeid
ScalarEvolution();

21
include/llvm/Analysis/ScalarEvolutionExpressions.h
View File

@@ -524,11 +524,26 @@ namespace llvm {
friend class ScalarEvolution;
friend class ScalarEvolution::SCEVCallbackVH;
// This should be an AssertingVH, however SCEVUnknowns are allocated in a
// BumpPtrAllocator so their destructors are never called.
/// V - The Value represented by this SCEVUnknown.
/// This should be an AssertingVH, however SCEVUnknowns are allocated in a
/// BumpPtrAllocator so their destructors are never called.
Value *V;
/// UpdateList - When values are RAUW'd with new values, and the new
/// values already have their own SCEVUnknowns, they can end up with
/// muliple SCEVUnknowns. This pointer links them all together so that
/// they can all be updated when another RAUW happens.
SCEVUnknown *UpdateList;
/// getUpdateListBack - Return the last SCEVUnknown in te UpdateList.
SCEVUnknown *getUpdateListBack() {
SCEVUnknown *P = this;
while (SCEVUnknown *Q = P->UpdateList) P = Q;
return P;
}
SCEVUnknown(const FoldingSetNodeIDRef ID, Value *v) :
SCEV(ID, scUnknown), V(v) {}
SCEV(ID, scUnknown), V(v), UpdateList(0) {}
public:
Value *getValue() const { return V; }