diff --git a/llvm/lib/CodeGen/LiveRangeEdit.cpp b/llvm/lib/CodeGen/LiveRangeEdit.cpp
index 2f65be51bb726..dc1121d7d9e28 100644
--- a/llvm/lib/CodeGen/LiveRangeEdit.cpp
+++ b/llvm/lib/CodeGen/LiveRangeEdit.cpp
@@ -75,11 +75,11 @@ void LiveRangeEdit::scanRemattable() {
     Register Original = VRM->getOriginal(getReg());
     LiveInterval &OrigLI = LIS.getInterval(Original);
     VNInfo *OrigVNI = OrigLI.getVNInfoAt(VNI->def);
-    if (!OrigVNI)
+    assert(OrigVNI && "Corrupt interval mapping?");
+    if (OrigVNI->isPHIDef())
       continue;
     MachineInstr *DefMI = LIS.getInstructionFromIndex(OrigVNI->def);
-    if (!DefMI)
-      continue;
+    assert(DefMI && "Missing instruction for def slot");
     if (TII.isReMaterializable(*DefMI))
       Remattable.insert(OrigVNI);
   }