From 3f95c88162cf319bce463d0e5e2d99a96c24dff6 Mon Sep 17 00:00:00 2001
From: Andrew Trick <atrick@apple.com>
Date: Wed, 27 Apr 2011 01:21:25 +0000
Subject: [PATCH] Fix for PR9633 [indvars] Assertion `isa<X>(Val) &&
 "cast<Ty>() argument 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 | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 3f69ce80f43..9396b07dab9 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/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;
     }