[CodeGen] Add begin-end iterators to MachineInstr

[javed.absar]

Summary

Probably there are more use cases of this,
but I got triggered by the one included in this patch

[kparzysz]

There is already MachineInstr::operands. Why do we need this?

[rovka]

include/llvm/CodeGen/MachineInstr.h

308 ↗

(On Diff #106643)

This looks identical to operands_begin/operands_end. I don't see a good reason for having both.
I don't know what to say about being concise vs being explicit in this context. @echristo, WDYT?

lib/Target/ARM/ARMMCInstLower.cpp

156

Unless I'm missing something (Friday evening etc etc), you can use

for (const auto &MO : MI->operands())

to the same effect.

[echristo]

lib/Target/ARM/ARMMCInstLower.cpp

156

Agreed, and it's more clear what you mean here.

[javed.absar]

Ok, I see that now too. Will use MI->operands() as suggested, as that will suffice.

[rovka]

LGTM.

[javed.absar]

Thanks Diana.

lib/Target/ARM/ARMMCInstLower.cpp

void llvm::LowerARMMachineInstrToMCInst(const MachineInstr *MI, MCInst &OutMI,
   case ARM::BICri:
   case ARM::RSBri:
   case ARM::RSBSri:
   case ARM::RSCri:
     EncodeImms = true;
     break;
   }
 
-  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
-    const MachineOperand &MO = MI->getOperand(i);
-
+  for (const MachineOperand &MO : MI->operands()) {
     MCOperand MCOp;
     if (AP.lowerOperand(MO, MCOp)) {
       if (MCOp.isImm() && EncodeImms) {
         int32_t Enc = ARM_AM::getSOImmVal(MCOp.getImm());
         if (Enc != -1)
           MCOp.setImm(Enc);
       }
       OutMI.addOperand(MCOp);