Index: lib/Analysis/ScalarEvolution.cpp
===================================================================
--- lib/Analysis/ScalarEvolution.cpp
+++ lib/Analysis/ScalarEvolution.cpp
@@ -4086,11 +4086,16 @@
 
 namespace {
 
+/// Takes SCEV S and Loop L. For each AddRec sub-expression, use its start
+/// expression in case its Loop is L. If it is not L then
+/// if IgnoreOtherLoops is true then use AddRec itself
+/// otherwise rewrite cannot be done.
+/// If SCEV contains non-invariant unknown SCEV rewrite cannot be done.
 class SCEVInitRewriter : public SCEVRewriteVisitor<SCEVInitRewriter> {
 public:
-  static const SCEV *rewrite(const SCEV *S, const Loop *L,
-                             ScalarEvolution &SE) {
-    SCEVInitRewriter Rewriter(L, SE);
+  static const SCEV *rewrite(const SCEV *S, const Loop *L, ScalarEvolution &SE,
+                             bool IgnoreOtherLoops = false) {
+    SCEVInitRewriter Rewriter(L, SE, IgnoreOtherLoops);
     const SCEV *Result = Rewriter.visit(S);
     return Rewriter.isValid() ? Result : SE.getCouldNotCompute();
   }
@@ -4105,17 +4110,20 @@
     // Only allow AddRecExprs for this loop.
     if (Expr->getLoop() == L)
       return Expr->getStart();
-    Valid = false;
+    // If we should not ignore other loops then invalidate result.
+    Valid = Valid && IgnoreOtherLoops;
     return Expr;
   }
 
   bool isValid() { return Valid; }
 
 private:
-  explicit SCEVInitRewriter(const Loop *L, ScalarEvolution &SE)
-      : SCEVRewriteVisitor(SE), L(L) {}
+  explicit SCEVInitRewriter(const Loop *L, ScalarEvolution &SE,
+                            bool IgnoreOtherLoops)
+      : SCEVRewriteVisitor(SE), L(L), IgnoreOtherLoops(IgnoreOtherLoops) {}
 
   const Loop *L;
+  const bool IgnoreOtherLoops;
   bool Valid = true;
 };