Fix for PR9633 [indvars] Assertion `isa<X>(Val) && "cast<Ty>() argume…

…nt of incompatible type!"' failed.

Added a type check in ScalarEvolution::computeSCEVAtScope to handle the case in which operands of an
AddRecExpr in the current scope are folded.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130271 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/ScalarEvolution.cpp

@@ -4701,9 +4701,14 @@ const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
       for (++i; i != e; ++i)
         NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
 
-      AddRec = cast<SCEVAddRecExpr>(
+      const SCEV *FoldedRec =
         getAddRecExpr(NewOps, AddRec->getLoop(),
-                      AddRec->getNoWrapFlags(SCEV::FlagNW)));
+                      AddRec->getNoWrapFlags(SCEV::FlagNW));
+      AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
+      // In cases with "undef" values, a loop's own recurrence may
+      // fold into a constant. Go ahead and return the optimistic value.
+      if (!AddRec)
+        return FoldedRec;
       break;
     }