[MachineOperand] Add a ChangeToGA method

[nhaehnle]

Summary

Analogous to the other ChangeToXXX methods. See the next patch for a
use case.

Change-Id: I6548d614706834fb9109ab3c8fe915e9c6ece2a7

[arsenm]

LGTM

include/llvm/CodeGen/MachineOperand.h

public:
   /// ChangeToFPImmediate - Replace this operand with a new FP immediate operand
   /// of the specified value.  If an operand is known to be an FP immediate
   /// already, the setFPImm method should be used.
   void ChangeToFPImmediate(const ConstantFP *FPImm);
 
   /// ChangeToES - Replace this operand with a new external symbol operand.
   void ChangeToES(const char *SymName, unsigned char TargetFlags = 0);
 
+  /// ChangeToGA - Replace this operand with a new global address operand.
+  void ChangeToGA(const GlobalValue *GV, int64_t Offset,
+                  unsigned char TargetFlags = 0);
+
   /// ChangeToMCSymbol - Replace this operand with a new MC symbol operand.
   void ChangeToMCSymbol(MCSymbol *Sym);
 
   /// Replace this operand with a frame index.
   void ChangeToFrameIndex(int Idx);
 
   /// Replace this operand with a target index.
   void ChangeToTargetIndex(unsigned Idx, int64_t Offset,

lib/CodeGen/MachineOperand.cpp

void MachineOperand::ChangeToES(const char *SymName,
   removeRegFromUses();
 
   OpKind = MO_ExternalSymbol;
   Contents.OffsetedInfo.Val.SymbolName = SymName;
   setOffset(0); // Offset is always 0.
   setTargetFlags(TargetFlags);
 }
 
+void MachineOperand::ChangeToGA(const GlobalValue *GV, int64_t Offset,
+                                unsigned char TargetFlags) {
+  assert((!isReg() || !isTied()) &&
+         "Cannot change a tied operand into a global address");
+
+  removeRegFromUses();
+
+  OpKind = MO_GlobalAddress;
+  Contents.OffsetedInfo.Val.GV = GV;
+  setOffset(Offset);
+  setTargetFlags(TargetFlags);
+}
+
 void MachineOperand::ChangeToMCSymbol(MCSymbol *Sym) {
   assert((!isReg() || !isTied()) &&
          "Cannot change a tied operand into an MCSymbol");
 
   removeRegFromUses();
 
   OpKind = MO_MCSymbol;
   Contents.Sym = Sym;