benchtests/bench-util.h

   1 /* Benchmark utility functions.
   2    Copyright (C) 2015-2023 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 /* Prevent compiler to optimize away call.  */
  20 #define DO_NOT_OPTIMIZE_OUT(value)                \
  21   ({                                              \
  22     __typeof (value) __v = (value);               \
  23     asm volatile ("" : : "r,m" (__v) : "memory"); \
  24     __v;                                          \
  25   })
  26
  27 #ifndef START_ITER
  28 # define START_ITER (100000000)
  29 #endif
  30
  31 /* bench_start reduces the random variations due to frequency scaling by
  32    executing a small loop with many memory accesses.  START_ITER controls
  33    the number of iterations.  */
  34
  35 void bench_start (void);