Remove val# defined by a remat'ed def that is now dead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58294 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/PreAllocSplitting.cpp b/lib/CodeGen/PreAllocSplitting.cpp
index 33e3e80..0969440 100644
--- a/lib/CodeGen/PreAllocSplitting.cpp
+++ b/lib/CodeGen/PreAllocSplitting.cpp
@@ -561,6 +561,9 @@
     SpillMI = prior(SpillPt);
     LIs->InsertMachineInstrInMaps(SpillMI, SpillIndex);
   } else if (!PrevSpilled) {
+    if (!DefMI)
+      // Def is dead. Do nothing.
+      return false;
     // If it's already split, just restore the value. There is no need to spill
     // the def again.
     // Check if it's possible to insert a spill after the def MI.