1 files changed, 38 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 8b3fc8d..9670e53 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -8410,6 +8410,44 @@ void ScalarEvolution::forgetValue(Value *V) {
   forgetMemoizedResults(ToForget);
 }
 
+void ScalarEvolution::forgetLcssaPhiWithNewPredecessor(Loop *L, PHINode *V) {
+  if (!isSCEVable(V->getType()))
+    return;
+
+  // If SCEV looked through a trivial LCSSA phi node, we might have SCEV's
+  // directly using a SCEVUnknown/SCEVAddRec defined in the loop. After an
+  // extra predecessor is added, this is no longer valid. Find all Unknowns and
+  // AddRecs defined in the loop and invalidate any SCEV's making use of them.
+  if (const SCEV *S = getExistingSCEV(V)) {
+    struct InvalidationRootCollector {
+      Loop *L;
+      SmallVector<const SCEV *, 8> Roots;
+
+      InvalidationRootCollector(Loop *L) : L(L) {}
+
+      bool follow(const SCEV *S) {
+        if (auto *SU = dyn_cast<SCEVUnknown>(S)) {
+          if (auto *I = dyn_cast<Instruction>(SU->getValue()))
+            if (L->contains(I))
+              Roots.push_back(S);
+        } else if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
+          if (L->contains(AddRec->getLoop()))
+            Roots.push_back(S);
+        }
+        return true;
+      }
+      bool isDone() const { return false; }
+    };
+
+    InvalidationRootCollector C(L);
+    visitAll(S, C);
+    forgetMemoizedResults(C.Roots);
+  }
+
+  // Also perform the normal invalidation.
+  forgetValue(V);
+}
+
 void ScalarEvolution::forgetLoopDispositions() { LoopDispositions.clear(); }
 
 void ScalarEvolution::forgetBlockAndLoopDispositions(Value *V) {