[ARM] Tidy up ARMBaseRegisterInfo implementation. NFC

[javed.absar]

Summary

This patch attempts to clean up and simplify ARMBaseRegisterInfo implementation a bit.

[fhahn]

Looks like a NFC, maybe address the style fix before committing.

lib/Target/ARM/ARMBaseRegisterInfo.cpp

662

I think there should be a space after &&

[javed.absar]

Thanks Florian. I will wait a bit for Renato/Diana to comment before committing, in case they have more comments/suggestions.

[rovka]

LGTM, thanks!

[rovka]

Actually, I do have one nit :)

lib/Target/ARM/ARMBaseRegisterInfo.cpp

199

While you're at it, you could also move markSuperRegs on its own line, it looks weird like this.

[javed.absar]

Good catch. Thanks. Will fix these and commit.

lib/Target/ARM/ARMBaseRegisterInfo.cpp

getReservedRegs(const MachineFunction &MF) const {
   if (STI.isR9Reserved())
     markSuperRegs(Reserved, ARM::R9);
   // Reserve D16-D31 if the subtarget doesn't support them.
   if (!STI.hasVFP3() || STI.hasD16()) {
     static_assert(ARM::D31 == ARM::D16 + 15, "Register list not consecutive!");
     for (unsigned R = 0; R < 16; ++R)
       markSuperRegs(Reserved, ARM::D16 + R);
   }
-  const TargetRegisterClass *RC  = &ARM::GPRPairRegClass;
-  for(TargetRegisterClass::iterator I = RC->begin(), E = RC->end(); I!=E; ++I)
-    for (MCSubRegIterator SI(*I, this); SI.isValid(); ++SI)
-      if (Reserved.test(*SI)) markSuperRegs(Reserved, *I);
+  const TargetRegisterClass &RC = ARM::GPRPairRegClass;
+  for (unsigned Reg : RC)
+    for (MCSubRegIterator SI(Reg, this); SI.isValid(); ++SI)
+      if (Reserved.test(*SI)) markSuperRegs(Reserved, Reg);
 
   assert(checkAllSuperRegsMarked(Reserved));
   return Reserved;
 }
 
 const TargetRegisterClass *
 ARMBaseRegisterInfo::getLargestLegalSuperClass(const TargetRegisterClass *RC,
                                                const MachineFunction &) const {
if (TargetRegisterInfo::isPhysicalRegister(Paired)) {
     PairedPhys = getPairedGPR(VRM->getPhys(Paired), Odd, this);
   }
 
   // First prefer the paired physreg.
   if (PairedPhys && is_contained(Order, PairedPhys))
     Hints.push_back(PairedPhys);
 
   // Then prefer even or odd registers.
-  for (unsigned I = 0, E = Order.size(); I != E; ++I) {
-    unsigned Reg = Order[I];
+  for (unsigned Reg : Order) {
     if (Reg == PairedPhys || (getEncodingValue(Reg) & 1) != Odd)
       continue;
     // Don't provide hints that are paired to a reserved register.
     unsigned Paired = getPairedGPR(Reg, !Odd, this);
     if (!Paired || MRI.isReserved(Paired))
       continue;
     Hints.push_back(Reg);
   }
void ARMBaseRegisterInfo::resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
   (void)Done;
 }
 
 bool ARMBaseRegisterInfo::isFrameOffsetLegal(const MachineInstr *MI, unsigned BaseReg,
                                              int64_t Offset) const {
   const MCInstrDesc &Desc = MI->getDesc();
   unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
   unsigned i = 0;
-
-  while (!MI->getOperand(i).isFI()) {
-    ++i;
-    assert(i < MI->getNumOperands() &&"Instr doesn't have FrameIndex operand!");
-  }
+  for (; !MI->getOperand(i).isFI(); ++i)
+    assert(i+1 < MI->getNumOperands() &&"Instr doesn't have FrameIndex operand!");
 
   // AddrMode4 and AddrMode6 cannot handle any offset.
   if (AddrMode == ARMII::AddrMode4 || AddrMode == ARMII::AddrMode6)
     return Offset == 0;
 
   unsigned NumBits = 0;
   unsigned Scale = 1;
   bool isSigned = true;