hwtime.h

来自「最新的sqlite3.6.2源代码」· C头文件 代码 · 共 88 行

/*
** 2008 May 27
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains inline asm code for retrieving "high-performance"
** counters for x86 class CPUs.
**
** $Id: hwtime.h,v 1.3 2008/08/01 14:33:15 shane Exp $
*/
#ifndef _HWTIME_H_
#define _HWTIME_H_

/*
** The following routine only works on pentium-class (or newer) processors.
** It uses the RDTSC opcode to read the cycle count value out of the
** processor and returns that value.  This can be used for high-res
** profiling.
*/
#if (defined(__GNUC__) || defined(_MSC_VER)) && \
      (defined(i386) || defined(__i386__) || defined(_M_IX86))

  #if defined(__GNUC__)

  __inline__ sqlite_uint64 sqlite3Hwtime(void){
     unsigned int lo, hi;
     __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
     return (sqlite_uint64)hi << 32 | lo;
  }

  #elif defined(_MSC_VER)

  __declspec(naked) __inline sqlite_uint64 __cdecl sqlite3Hwtime(void){
     __asm {
        rdtsc
        ret       ; return value at EDX:EAX
     }
  }

  #endif

#elif (defined(__GNUC__) && defined(__x86_64__))

  __inline__ sqlite_uint64 sqlite3Hwtime(void){
      unsigned long val;
      __asm__ __volatile__ ("rdtsc" : "=A" (val));
      return val;
  }
 
#elif (defined(__GNUC__) && defined(__ppc__))

  __inline__ sqlite_uint64 sqlite3Hwtime(void){
      unsigned long long retval;
      unsigned long junk;
      __asm__ __volatile__ ("\n\
          1:      mftbu   %1\n\
                  mftb    %L0\n\
                  mftbu   %0\n\
                  cmpw    %0,%1\n\
                  bne     1b"
                  : "=r" (retval), "=r" (junk));
      return retval;
  }

#else

  #error Need implementation of sqlite3Hwtime() for your platform.

  /*
  ** To compile without implementing sqlite3Hwtime() for your platform,
  ** you can remove the above #error and use the following
  ** stub function.  You will lose timing support for many
  ** of the debugging and testing utilities, but it should at
  ** least compile and run.
  */
  sqlite_uint64 sqlite3Hwtime(void){ return ((sqlite_uint64)0); }

#endif

#endif /* !defined(_HWTIME_H_) */