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

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

2 files changed, 23 insertions, 3 deletions

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index 1b27efb..b052a82 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -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();
diff --git a/include/llvm/Analysis/ScalarEvolutionExpressions.h b/include/llvm/Analysis/ScalarEvolutionExpressions.h
index ec4ac07..03f147e 100644
--- a/include/llvm/Analysis/ScalarEvolutionExpressions.h
+++ b/include/llvm/Analysis/ScalarEvolutionExpressions.h
@@ -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; }