diff --git a/llvm/include/llvm/CodeGen/RegisterScavenging.h b/llvm/include/llvm/CodeGen/RegisterScavenging.h
index 0eb2b2ab07f7..49d16892f87a 100644
--- a/llvm/include/llvm/CodeGen/RegisterScavenging.h
+++ b/llvm/include/llvm/CodeGen/RegisterScavenging.h
@@ -42,7 +42,7 @@ class RegScavenger {
 
   /// Information on scavenged registers (held in a spill slot).
   struct ScavengedInfo {
-    ScavengedInfo(int FI) : FrameIndex(FI), Reg(0), Restore(NULL) {}
+    ScavengedInfo(int FI = -1) : FrameIndex(FI), Reg(0), Restore(NULL) {}
 
     /// A spill slot used for scavenging a register post register allocation.
     int FrameIndex;
@@ -130,7 +130,8 @@ public:
   void getScavengingFrameIndices(SmallVectorImpl<int> &A) const {
     for (SmallVector<ScavengedInfo, 2>::const_iterator I = Scavenged.begin(),
          IE = Scavenged.end(); I != IE; ++I)
-      A.push_back(I->FrameIndex);
+      if (I->FrameIndex >= 0)
+        A.push_back(I->FrameIndex);
   }
 
   /// scavengeRegister - Make a register of the specific register class
diff --git a/llvm/lib/CodeGen/RegisterScavenging.cpp b/llvm/lib/CodeGen/RegisterScavenging.cpp
index 4c85644e1a35..6b85cd93cf32 100644
--- a/llvm/lib/CodeGen/RegisterScavenging.cpp
+++ b/llvm/lib/CodeGen/RegisterScavenging.cpp
@@ -371,8 +371,11 @@ unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
     if (Scavenged[SI].Reg == 0)
       break;
 
-  assert(SI < Scavenged.size() &&
-         "Scavenger slots are live, unable to scavenge another register!");
+  if (SI < Scavenged.size()) {
+    // We need to scavenge a register but have no spill slot, the target
+    // must know how to do it (if not, we'll assert below).
+    Scavenged.push_back(ScavengedInfo());
+  }
 
   // Avoid infinite regress
   Scavenged[SI].Reg = SReg;