[ARM] CodeGen: New helpers for getting pred/CC operands. NFC

[rovka]

Summary

Add helpers that create MachineOperands for predicates / condition code results
needed by instructions in the ARM backend. These are intended to replace the
AddDefaultPred/AddDefaultCC helpers.

Patches removing AddDefaultPred/CC follow. I can squash them before committing,
but I thought it would be easier to review this way.

[MatzeB]

LGTM.
As you proposed I would squash this with D28555 before committing.

[rovka]

Squashed with D28555. Thanks for reviewing!

lib/Target/ARM/ARMBaseInstrInfo.h

bool canCauseFpMLxStall(unsigned Opcode) const {
     return MLxHazardOpcodes.count(Opcode);
   }
 
   /// Returns true if the instruction has a shift by immediate that can be
   /// executed in one cycle less.
   bool isSwiftFastImmShift(const MachineInstr *MI) const;
 };
 
+/// Get the operands corresponding to the given \p Pred value. By default, the
+/// predicate register is assumed to be 0 (no register), but you can pass in a
+/// \p PredReg if that is not the case.
+static inline std::array<MachineOperand, 2> predOps(ARMCC::CondCodes Pred,
+                                                    unsigned PredReg = 0) {
+  return {{MachineOperand::CreateImm(static_cast<int64_t>(Pred)),
+           MachineOperand::CreateReg(PredReg, 0)}};
+}
+
+/// Get the operand corresponding to the conditional code result. By default,
+/// this is 0 (no register).
+static inline MachineOperand condCodeOp(unsigned CCReg = 0) {
+  return MachineOperand::CreateReg(CCReg, 0);
+}
+
+// FIXME: Remove when all uses are gone.
 static inline
 const MachineInstrBuilder &AddDefaultPred(const MachineInstrBuilder &MIB) {
   return MIB.addImm((int64_t)ARMCC::AL).addReg(0);
 }
 
+// FIXME: Remove when all uses are gone.
 static inline
 const MachineInstrBuilder &AddDefaultCC(const MachineInstrBuilder &MIB) {
   return MIB.addReg(0);
 }
 
+// FIXME: Replace with something that returns a MachineOperand directly.
 static inline
 const MachineInstrBuilder &AddDefaultT1CC(const MachineInstrBuilder &MIB,
                                           bool isDead = false) {
   return MIB.addReg(ARM::CPSR, getDefRegState(true) | getDeadRegState(isDead));
 }
 
+// FIXME: Replace with something that returns a MachineOperand directly.
 static inline
 const MachineInstrBuilder &AddNoT1CC(const MachineInstrBuilder &MIB) {
   return MIB.addReg(0);
 }
 
 static inline
 bool isUncondBranchOpcode(int Opc) {
   return Opc == ARM::B || Opc == ARM::tB || Opc == ARM::t2B;