Drop unused rdtsc instruction.

src/x64/disasm-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1211 matching lines @@
     current += PrintRightXMMOperand(current);
 
   } else if (opcode == 0x29) {
     // movaps xmm/m128, xmm
     int mod, regop, rm;
     get_modrm(*current, &mod, &regop, &rm);
     AppendToBuffer("movaps ");
     current += PrintRightXMMOperand(current);
     AppendToBuffer(", %s", NameOfXMMRegister(regop));
 
-  } else if (opcode == 0xA2 || opcode == 0x31) {
-    // RDTSC or CPUID
+  } else if (opcode == 0xA2) {
+    // CPUID
     AppendToBuffer("%s", mnemonic);
 
   } else if ((opcode & 0xF0) == 0x40) {
     // CMOVcc: conditional move.
     int condition = opcode & 0x0F;
     const InstructionDesc& idesc = cmov_instructions[condition];
     byte_size_operand_ = idesc.byte_size_operation;
     current += PrintOperands(idesc.mnem, idesc.op_order_, current);
 
   } else if (opcode == 0x57) {
@@ skipping 43 matching lines @@
 
 // Mnemonics for two-byte opcode instructions starting with 0x0F.
 // The argument is the second byte of the two-byte opcode.
 // Returns NULL if the instruction is not handled here.
 const char* DisassemblerX64::TwoByteMnemonic(byte opcode) {
   switch (opcode) {
     case 0x1F:
       return "nop";
     case 0x2A:  // F2/F3 prefix.
       return "cvtsi2s";
-    case 0x31:
-      return "rdtsc";
     case 0x51:  // F2 prefix.
       return "sqrtsd";
     case 0x58:  // F2 prefix.
       return "addsd";
     case 0x59:  // F2 prefix.
       return "mulsd";
     case 0x5C:  // F2 prefix.
       return "subsd";
     case 0x5E:  // F2 prefix.
       return "divsd";
@@ skipping 556 matching lines @@
     for (int i = 6 - static_cast<int>(pc - prev_pc); i >= 0; i--) {
       fprintf(f, "  ");
     }
     fprintf(f, "  %s\n", buffer.start());
   }
 }
 
 }  // namespace disasm
 
 #endif  // V8_TARGET_ARCH_X64