[Mips] Silencing warnings in instruction info (NFC)

[NikolaPrica]

Summary

isORCopyInst and isReadOrWriteToDSPReg functions were producing warning that some statements my fall through.

[atanasyan]

lib/Target/Mips/MipsSEInstrInfo.cpp

211

I would set isWrite = false here so this function always returns a correct value for the isWrite and does not have to rely on proper initialization of the isWrite before calling.

lib/Target/Mips/MipsSEInstrInfo.cpp

if (SrcReg)
     MIB.addReg(SrcReg, getKillRegState(KillSrc));
 
   if (ZeroReg)
     MIB.addReg(ZeroReg);
 }
 
 static bool isORCopyInst(const MachineInstr &MI) {
   switch (MI.getOpcode()) {
+  default:
+    break;
   case Mips::OR_MM:
   case Mips::OR:
     if (MI.getOperand(2).getReg() == Mips::ZERO)
       return true;
+    break;
   case Mips::OR64:
     if (MI.getOperand(2).getReg() == Mips::ZERO_64)
       return true;
-  default:
-      return false;
+    break;
   }
+  return false;
 }
 
 /// If @MI is WRDSP/RRDSP instruction return true with @isWrite set to true
 /// if it is WRDSP instruction.
-static bool isReadOrWritToDSPReg(const MachineInstr &MI, bool &isWrite) {
+static bool isReadOrWriteToDSPReg(const MachineInstr &MI, bool &isWrite) {
   switch (MI.getOpcode()) {
-    case Mips::WRDSP:
-    case Mips::WRDSP_MM:
-      isWrite = true;
-    case Mips::RDDSP:
-    case Mips::RDDSP_MM:
-      return true;
-    default:
-     return false;
+  default:
+   return false;
+    break;
+    isWrite = false;
+    break;
   }
+  return true;
 }
 
 /// We check for the common case of 'or', as it's MIPS' preferred instruction
 /// for GPRs but we have to check the operands to ensure that is the case.
 /// Other move instructions for MIPS are directly identifiable.
 bool MipsSEInstrInfo::isCopyInstr(const MachineInstr &MI,
                                   const MachineOperand *&Src,
                                   const MachineOperand *&Dest) const {
   bool isDSPControlWrite = false;
   // Condition is made to match the creation of WRDSP/RDDSP copy instruction
   // from copyPhysReg function.
-  if (isReadOrWritToDSPReg(MI, isDSPControlWrite)) {
+  if (isReadOrWriteToDSPReg(MI, isDSPControlWrite)) {
     if (!MI.getOperand(1).isImm() || MI.getOperand(1).getImm() != (1<<4))
       return false;
     else if (isDSPControlWrite) {
       Src = &MI.getOperand(0);
       Dest = &MI.getOperand(2);
     } else {
       Dest = &MI.getOperand(0);
       Src = &MI.getOperand(2);