TargetInstrInfo: add virtual function getInstSizeInBytes

This adds a target hook getInstSizeInBytes to TargetInstrInfo that a lot of
subclasses already implement.

Differential Revision: https://reviews.llvm.org/D22885

llvm-svn: 277126
diff --git a/llvm/lib/Target/Mips/MipsInstrInfo.h b/llvm/lib/Target/Mips/MipsInstrInfo.h
index bb0b306..876e9f9 100644
--- a/llvm/lib/Target/Mips/MipsInstrInfo.h
+++ b/llvm/lib/Target/Mips/MipsInstrInfo.h
@@ -92,7 +92,7 @@
   virtual unsigned getOppositeBranchOpc(unsigned Opc) const = 0;
 
   /// Return the number of bytes of code the specified instruction may be.
-  unsigned getInstSizeInBytes(const MachineInstr &MI) const;
+  unsigned getInstSizeInBytes(const MachineInstr &MI) const override;
 
   void storeRegToStackSlot(MachineBasicBlock &MBB,
                            MachineBasicBlock::iterator MBBI,