sysdeps/loongarch/cpu-tunables.c

   1 /* LoongArch CPU feature tuning.
   2    This file is part of the GNU C Library.
   3    Copyright (C) 2024 Free Software Foundation, Inc.
   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    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <stdbool.h>
  20 #include <stdint.h>
  21 #include <unistd.h>             /* Get STDOUT_FILENO for _dl_printf.  */
  22 #include <elf/dl-tunables.h>
  23 #include <string.h>
  24 #include <cpu-features.h>
  25 #include <ldsodefs.h>
  26 #include <sys/auxv.h>
  27 #include <dl-tunables-parse.h>
  28 #include <dl-symbol-redir-ifunc.h>
  29
  30 #define CHECK_GLIBC_IFUNC_CPU(f, name, len)                     \
  31   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);        \
  32   if (tunable_str_comma_strcmp_cte (&f, #name))                         \
  33     {                                                                   \
  34       if (f.disable)                                                    \
  35         GLRO(dl_larch_cpu_features).hwcap &= (~HWCAP_LOONGARCH_##name); \
  36       else                                                              \
  37         GLRO(dl_larch_cpu_features).hwcap |= HWCAP_LOONGARCH_##name;    \
  38       break;                                                            \
  39     }
  40
  41 attribute_hidden void
  42 TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
  43 {
  44   /* The current IFUNC selection is based on microbenchmarks in glibc.
  45      It should give the best performance for most workloads.  But other
  46      choices may have better performance for a particular workload or on
  47      the hardware which wasn't available when the selection was made.
  48      The environment variable:
  49
  50      GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,-zzz,....
  51
  52      can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature
  53      yyy and zzz, where the feature name is case-sensitive and has to
  54      match the ones in cpu-features.h.  It can be used by glibc developers
  55      to tune for a new processor or override the IFUNC selection to
  56      improve performance for a particular workload.
  57
  58      NOTE: the IFUNC selection may change over time.  Please check all
  59      multiarch implementations when experimenting.  */
  60
  61   struct tunable_str_comma_state_t ts;
  62   tunable_str_comma_init (&ts, valp);
  63
  64   struct tunable_str_comma_t n;
  65   while (tunable_str_comma_next (&ts, &n))
  66     {
  67       switch (n.len)
  68         {
  69         default:
  70           break;
  71         case 3:
  72           {
  73             CHECK_GLIBC_IFUNC_CPU (n, LSX, 3);
  74             CHECK_GLIBC_IFUNC_CPU (n, UAL, 3);
  75           }
  76           break;
  77         case 4:
  78           {
  79             CHECK_GLIBC_IFUNC_CPU (n, LASX, 4);
  80           }
  81           break;
  82         }
  83     }
  84
  85   /* Ensure that the user has not enabled any unsupported features.  */
  86   GLRO(dl_larch_cpu_features).hwcap &= GLRO(dl_hwcap);
  87 }