diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 5cd9739e223..a71db865cbf 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -2309,10 +2309,20 @@ void ScalarEvolution::forgetLoopBackedgeTakenCount(const Loop *L) {
 void ScalarEvolution::forgetLoopPHIs(const Loop *L) {
   BasicBlock *Header = L->getHeader();
 
+  // Push all Loop-header PHIs onto the Worklist stack, except those
+  // that are presently represented via a SCEVUnknown. SCEVUnknown for
+  // a PHI either means that it has an unrecognized structure, or it's
+  // a PHI that's in the progress of being computed by createNodeForPHI.
+  // In the former case, additional loop trip count information isn't
+  // going to change anything. In the later case, createNodeForPHI will
+  // perform the necessary updates on its own when it gets to that point.
   SmallVector<Instruction *, 16> Worklist;
   for (BasicBlock::iterator I = Header->begin();
-       PHINode *PN = dyn_cast<PHINode>(I); ++I)
-    Worklist.push_back(PN);
+       PHINode *PN = dyn_cast<PHINode>(I); ++I) {
+    std::map<SCEVCallbackVH, SCEVHandle>::iterator It = Scalars.find((Value*)I);
+    if (It != Scalars.end() && !isa<SCEVUnknown>(It->second))
+      Worklist.push_back(PN);
+  }
 
   while (!Worklist.empty()) {
     Instruction *I = Worklist.pop_back_val();
diff --git a/test/Transforms/IndVarSimplify/loop_evaluate_5.ll b/test/Transforms/IndVarSimplify/loop_evaluate_5.ll
new file mode 100644
index 00000000000..c6ce4a2122d
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/loop_evaluate_5.ll
@@ -0,0 +1,32 @@
+; RUN: llvm-as < %s | opt -indvars | llvm-dis | grep {120, %bb2.bb3_crit_edge}
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64"
+target triple = "i686-pc-linux-gnu"
+
+; Indvars should be able to compute an exit value for %tmp1.
+
+define i32 @testcase(i5 zeroext %k) nounwind readnone {
+entry:
+	br i1 false, label %bb3, label %bb.nph
+
+bb.nph:		; preds = %entry
+	br label %bb
+
+bb:		; preds = %bb2, %bb.nph
+	%result2 = phi i32 [ %tmp1, %bb2 ], [ 0, %bb.nph ]		; <i32> [#uses=1]
+	%k_01 = phi i5 [ %indvar_next1, %bb2 ], [ 0, %bb.nph ]		; <i5> [#uses=2]
+	%tmp2 = zext i5 %k_01 to i32		; <i32> [#uses=1]
+	%tmp1 = add i32 %tmp2, %result2		; <i32> [#uses=2]
+	%indvar_next1 = add i5 %k_01, 1		; <i5> [#uses=2]
+	br label %bb2
+
+bb2:		; preds = %bb
+	%phitmp = icmp eq i5 %indvar_next1, -16		; <i1> [#uses=1]
+	br i1 %phitmp, label %bb2.bb3_crit_edge, label %bb
+
+bb2.bb3_crit_edge:		; preds = %bb2
+	br label %bb3
+
+bb3:		; preds = %bb2.bb3_crit_edge, %entry
+	%result.lcssa = phi i32 [ %tmp1, %bb2.bb3_crit_edge ], [ 0, %entry ]		; <i32> [#uses=1]
+	ret i32 %result.lcssa
+}