Auto-sandboxing: Switch to automatic scratch register invalidation

lib/Target/ARM/MCTargetDesc/ARMMCNaClExpander.h

 //===- ARMMCNaClExpander.h --------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the ARMMCNaClExpander class, the ARM specific
@@ skipping 16 matching lines @@
 namespace ARM {
 class ARMMCNaClExpander : public MCNaClExpander {
 public:
   ARMMCNaClExpander(const MCContext &Ctx, std::unique_ptr<MCRegisterInfo> &&RI,
                     std::unique_ptr<MCInstrInfo> &&II)
       : MCNaClExpander(Ctx, std::move(RI), std::move(II)) {}
 
   bool expandInst(const MCInst &Inst, MCStreamer &Out,
                   const MCSubtargetInfo &STI) override;
 
+protected:
+  bool isValidScratchRegister(unsigned Reg) const override;
+
 private:
   bool Guard = false; // recursion guard
   int SaveCount = 0;
 
   void expandIndirectBranch(const MCInst &Inst, MCStreamer &Out,
                             const MCSubtargetInfo &STI, bool isCall);
 
   void expandCall(const MCInst &Inst, MCStreamer &Out,
                   const MCSubtargetInfo &STI);
 
   void doExpandInst(const MCInst &Inst, MCStreamer &Out,
                     const MCSubtargetInfo &STI);
 };
 }
 }
 #endif