Refactor LiveRangeEdit::eliminateDeadDefs.

I want to add logic to handle more cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184571 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LiveRangeEdit.h

@@ -19,6 +19,7 @@
 #define LLVM_CODEGEN_LIVERANGEEDIT_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/CodeGen/LiveInterval.h"
 #include "llvm/Target/TargetMachine.h"
@@ -90,6 +91,12 @@ private:
   /// a load, eliminate the register by folding the def into the use.
   bool foldAsLoad(LiveInterval *LI, SmallVectorImpl<MachineInstr*> &Dead);
 
+  typedef SetVector<LiveInterval*,
+                    SmallVector<LiveInterval*, 8>,
+                    SmallPtrSet<LiveInterval*, 8> > ToShrinkSet;
+  /// Helper for eliminateDeadDefs.
+  void eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink);
+
 public:
   /// Create a LiveRangeEdit for breaking down parent into smaller pieces.
   /// @param parent The register being spilled or split.