CodeGen: Add another method to MachineInstrBuilder. NFC

[rovka]

Summary

Add a method that allows adding multiple operands simultaneously to a
MachineInstrBuilder. This is especially useful for operands that are closely
related, such as those representing the predicate on ARM instructions (one
immediate + one register operand).

[MatzeB]

LGTM

include/llvm/CodeGen/MachineInstrBuilder.h

195

The const is unnecessary for immutable classes like ArrayRef or StringRef (though it doesn't hurt either).

196

MachineOperand instead of auto would be friendlier for readers.

[rovka]

Squashed with D28555. Thanks for reviewing!

include/llvm/CodeGen/MachineInstrBuilder.h

const MachineInstrBuilder &setMemRefs(std::pair<MachineInstr::mmo_iterator,
     return *this;
   }
 
   const MachineInstrBuilder &addOperand(const MachineOperand &MO) const {
     MI->addOperand(*MF, MO);
     return *this;
   }
 
+  const MachineInstrBuilder &add(const ArrayRef<MachineOperand> MOs) const {
+    for (const auto &MO : MOs) {
+      MI->addOperand(*MF, MO);
+    }
+    return *this;
+  }
+
   const MachineInstrBuilder &addMetadata(const MDNode *MD) const {
     MI->addOperand(*MF, MachineOperand::CreateMetadata(MD));
     assert((MI->isDebugValue() ? static_cast<bool>(MI->getDebugVariable())
                                : true) &&
            "first MDNode argument of a DBG_VALUE not a variable");
     return *this;
   }