[BOLT][NFC] Use X86 mnemonic checks

[Amir]

Summary

Remove switches in X86MCPlusBuilder.cpp, use mnemonic checks instead

[Amir]

isPrefix

[rafauler]

LGTM

bolt/lib/Target/X86/X86MCPlusBuilder.cpp

bool isUnconditionalBranch(const MCInst &Inst) const override {
     return Analysis->isUnconditionalBranch(Inst) && !isTailCall(Inst);
   }
 
   bool isNoop(const MCInst &Inst) const override {
     return X86::isNOP(Inst.getOpcode());
   }
 
   unsigned getCondCode(const MCInst &Inst) const override {
-    switch (Inst.getOpcode()) {
-    default:
-      return X86::COND_INVALID;
-    case X86::JCC_1:
-    case X86::JCC_2:
-    case X86::JCC_4:
-      return Inst.getOperand(Info->get(Inst.getOpcode()).NumOperands - 1)
-          .getImm();
-    }
+    unsigned Opcode = Inst.getOpcode();
+    if (X86::isJCC(Opcode))
+      return Inst.getOperand(Info->get(Opcode).NumOperands - 1).getImm();
   }
 
   unsigned getInvertedCondCode(unsigned CC) const override {
     switch (CC) {
     default: return X86::COND_INVALID;
     case X86::COND_E:  return X86::COND_NE;
     case X86::COND_NE: return X86::COND_E;
     case X86::COND_L:  return X86::COND_GE;
if (Inst.getFlags() == X86::IP_HAS_REPEAT) {
       Inst.setFlags(0);
       return true;
     }
     return false;
   }
 
   // FIXME: For compatibility with old LLVM only!
   bool isTerminator(const MCInst &Inst) const override {
-    if (Info->get(Inst.getOpcode()).isTerminator())
-      return true;
-    switch (Inst.getOpcode()) {
-    default:
-      return false;
-    case X86::TRAP:
-    // Opcodes previously known as X86::UD2B
-    case X86::UD1Wm:
-    case X86::UD1Lm:
-    case X86::UD1Qm:
-    case X86::UD1Wr:
-    case X86::UD1Lr:
-    case X86::UD1Qr:
-      return true;
-    }
+    unsigned Opcode = Inst.getOpcode();
+    return Info->get(Opcode).isTerminator() || X86::isUD1(Opcode) ||
+           X86::isUD2(Opcode);
   }
 
   bool isIndirectCall(const MCInst &Inst) const override {
     return isCall(Inst) &&
            ((getMemoryOperandNo(Inst) != -1) || Inst.getOperand(0).isReg());
   }
 
   bool isPop(const MCInst &Inst) const override {