Drop unused rdtsc instruction.

src/x64/assembler-x64.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 457 matching lines @@
   // Detect features of the target CPU. Set safe defaults if the serializer
   // is enabled (snapshots must be portable).
   static void Probe();
 
   // Check whether a feature is supported by the target CPU.
   static bool IsSupported(CpuFeature f) {
     ASSERT(initialized_);
     if (f == SSE3 && !FLAG_enable_sse3) return false;
     if (f == SSE4_1 && !FLAG_enable_sse4_1) return false;
     if (f == CMOV && !FLAG_enable_cmov) return false;
-    if (f == RDTSC && !FLAG_enable_rdtsc) return false;
     if (f == SAHF && !FLAG_enable_sahf) return false;
     return (supported_ & (static_cast<uint64_t>(1) << f)) != 0;
   }
 
   static bool IsFoundByRuntimeProbingOnly(CpuFeature f) {
     ASSERT(initialized_);
     return (found_by_runtime_probing_only_ &
             (static_cast<uint64_t>(1) << f)) != 0;
   }
 
@@ skipping 680 matching lines @@
   void bt(const Operand& dst, Register src);
   void bts(const Operand& dst, Register src);
 
   // Miscellaneous
   void clc();
   void cld();
   void cpuid();
   void hlt();
   void int3();
   void nop();
-  void rdtsc();
   void ret(int imm16);
   void setcc(Condition cc, Register reg);
 
   // Label operations & relative jumps (PPUM Appendix D)
   //
   // Takes a branch opcode (cc) and a label (L) and generates
   // either a backward branch or a forward branch and links it
   // to the label fixup chain. Usage:
   //
   // Label L;    // unbound label
@@ skipping 469 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_