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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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74
lib/Analysis/ScalarEvolution.cpp
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@@ -3660,29 +3660,59 @@ void ScalarEvolution::forgetLoop(const Loop *L) {
}
}
/// forgetValue - This method should be called by the client when it has
/// changed a value in a way that may effect its value, or which may
/// disconnect it from a def-use chain linking it to a loop.
void ScalarEvolution::forgetValue(Value *V) {
// 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.
//
/// 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 ScalarEvolution::forgetSCEVUnknown(Value *V, Value *NewV) {
// This permits SCEV pointers to be used as keys in maps
// such as the ValuesAtScopes map.
// Check for an exisitng SCEVUnknown for V in the uniquing map.
FoldingSetNodeID ID;
ID.AddInteger(scUnknown);
ID.AddPointer(V);
void *IP;
if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
// Remove the old SCEVUnknown from the uniquing map, effectively
// leaking it from subsequent use by ScalarEvolution. There
// may be existing SCEVs live which still point to it though.
UniqueSCEVs.RemoveNode(S);
// This isn't necessary, but we might as well remove the
// value from the ValuesAtScopes map too.
ValuesAtScopes.erase(S);
// If there's a replacement value, update the old SCEVUnknowns
// so that SCEVs which still point to it see the new value.
if (NewV) {
// Update the old SCEVUnknown and all SCEVUnknowns on its update list
// to point to NewV instead of V.
for (SCEVUnknown *U = cast<SCEVUnknown>(S); U; U = U->UpdateList) {
assert(U->V == V && "SCEVUnknown update list is inconsistent!");
U->V = NewV;
}
// Check for an existing SCEVUnknown for NewV in the uniquing map.
ID.clear();
ID.AddInteger(scUnknown);
ID.AddPointer(NewV);
if (SCEV *NewS = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
// The uniquing map already had an entry for the new
// value. Append the old SCEVUnknown (and its update list) to the
// new SCEVUnknown's update list.
cast<SCEVUnknown>(NewS)->getUpdateListBack()->UpdateList =
cast<SCEVUnknown>(S);
} else {
// The uniquing map did not have an entry for the new
// value yet. Set the old SCEVUnknown, which has now been
// updated, to be the SCEVUnknown in the uniquing map.
UniqueSCEVs.InsertNode(S, IP);
}
}
}
}
/// forgetValue - This method should be called by the client when it has
/// changed a value in a way that may effect its value, or which may
/// disconnect it from a def-use chain linking it to a loop.
void ScalarEvolution::forgetValue(Value *V) {
forgetSCEVUnknown(V, 0);
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return;
@@ -5692,24 +5722,10 @@ void ScalarEvolution::SCEVCallbackVH::deleted() {
void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *V) {
assert(SE && "SCEVCallbackVH called with a null ScalarEvolution!");
Value *Old = getValPtr();
// If there's a SCEVUnknown tying this value into the SCEV
// space, replace the SCEVUnknown's value with the new value
// for the benefit of any SCEVs still referencing it, and
// and remove it from the folding set map so that new scevs
// don't reference it.
FoldingSetNodeID ID;
ID.AddInteger(scUnknown);
ID.AddPointer(Old);
void *IP;
if (SCEVUnknown *S = cast_or_null<SCEVUnknown>(
SE->UniqueSCEVs.FindNodeOrInsertPos(ID, IP))) {
S->V = V;
SE->UniqueSCEVs.RemoveNode(S);
SE->ValuesAtScopes.erase(S);
}
// First, update existing SCEVUnknowns.
SE->forgetSCEVUnknown(Old, V);
// Forget all the expressions associated with users of the old value,
// so that future queries will recompute the expressions using the new