1  /* High precision, low overhead timing functions.  x86 version.
       2     Copyright (C) 2018-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #ifndef _HP_TIMING_H
      20  #define _HP_TIMING_H	1
      21  
      22  #include <isa.h>
      23  
      24  #if MINIMUM_ISA == 686 || MINIMUM_ISA == 8664
      25  /* We indeed have inlined functions.  */
      26  # define HP_TIMING_INLINE	(1)
      27  
      28  /* We use 64bit values for the times.  */
      29  typedef unsigned long long int hp_timing_t;
      30  
      31  /* That's quite simple.  Use the `rdtsc' instruction.  Note that the value
      32     might not be 100% accurate since there might be some more instructions
      33     running in this moment.  This could be changed by using a barrier like
      34     'cpuid' right before the `rdtsc' instruction.  But we are not interested
      35     in accurate clock cycles here so we don't do this.
      36  
      37     NB: Use __builtin_ia32_rdtsc directly since including <x86intrin.h>
      38     makes building glibc very slow.  */
      39  # ifdef USE_RDTSCP
      40  /* RDTSCP waits until all previous instructions have executed and all
      41     previous loads are globally visible before reading the counter.
      42     RDTSC doesn't wait until all previous instructions have been executed
      43     before reading the counter.  */
      44  #  define HP_TIMING_NOW(Var) \
      45    (__extension__ ({				\
      46      unsigned int __aux;				\
      47      (Var) = __builtin_ia32_rdtscp (&__aux);	\
      48    }))
      49  # else
      50  #  define HP_TIMING_NOW(Var) ((Var) = __builtin_ia32_rdtsc ())
      51  # endif
      52  
      53  # include <hp-timing-common.h>
      54  #else
      55  /* NB: Undefine _HP_TIMING_H so that <sysdeps/generic/hp-timing.h> will
      56     be included.  */
      57  # undef _HP_TIMING_H
      58  # include <sysdeps/generic/hp-timing.h>
      59  #endif
      60  
      61  #endif /* hp-timing.h */