libatomic/config/x86/host-config.h

   1 /* Copyright (C) 2012-2021 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU Atomic Library (libatomic).
   5
   6    Libatomic is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
  12    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14    more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 #if HAVE_IFUNC
  26 #include <cpuid.h>
  27
  28 #ifdef __x86_64__
  29 # define FEAT1_REGISTER ecx
  30 #else
  31 # define FEAT1_REGISTER edx
  32 #endif
  33
  34 /* Value of the CPUID feature register FEAT1_REGISTER for the cmpxchg
  35    bit for IFUNC_COND1 below.  */
  36 extern unsigned int __libat_feat1 HIDDEN;
  37
  38 /* Initialize libat_feat1 and return its value.  */
  39 unsigned int __libat_feat1_init (void) HIDDEN;
  40
  41 /* Return the value of the relevant feature register for the relevant
  42    cmpxchg bit, or 0 if there is no CPUID support.  */
  43 static inline unsigned int
  44 __attribute__ ((const))
  45 load_feat1 (void)
  46 {
  47   /* See the store in __libat_feat1_init.  */
  48   unsigned int feat1 = __atomic_load_n (&__libat_feat1, __ATOMIC_RELAXED);
  49   if (feat1 == 0)
  50     /* Assume that initialization has not happened yet.  This may get
  51        called repeatedly if the CPU does not have any feature bits at
  52        all.  */
  53     feat1 = __libat_feat1_init ();
  54   return feat1;
  55 }
  56
  57 #ifdef __x86_64__
  58 # define IFUNC_COND_1   (load_feat1 () & bit_CMPXCHG16B)
  59 #else
  60 # define IFUNC_COND_1   (load_feat1 () & bit_CMPXCHG8B)
  61 #endif
  62
  63 #ifdef __x86_64__
  64 # define IFUNC_NCOND(N) (N == 16)
  65 #else
  66 # define IFUNC_NCOND(N) (N == 8)
  67 #endif
  68
  69 #ifdef __x86_64__
  70 # undef MAYBE_HAVE_ATOMIC_CAS_16
  71 # define MAYBE_HAVE_ATOMIC_CAS_16       IFUNC_COND_1
  72 # undef MAYBE_HAVE_ATOMIC_EXCHANGE_16
  73 # define MAYBE_HAVE_ATOMIC_EXCHANGE_16  IFUNC_COND_1
  74 # undef MAYBE_HAVE_ATOMIC_LDST_16
  75 # define MAYBE_HAVE_ATOMIC_LDST_16      IFUNC_COND_1
  76 /* Since load and store are implemented with CAS, they are not fast.  */
  77 # undef FAST_ATOMIC_LDST_16
  78 # define FAST_ATOMIC_LDST_16            0
  79 # if IFUNC_ALT == 1
  80 #  undef HAVE_ATOMIC_CAS_16
  81 #  define HAVE_ATOMIC_CAS_16 1
  82 # endif
  83 #else
  84 # undef MAYBE_HAVE_ATOMIC_CAS_8
  85 # define MAYBE_HAVE_ATOMIC_CAS_8        IFUNC_COND_1
  86 # undef MAYBE_HAVE_ATOMIC_EXCHANGE_8
  87 # define MAYBE_HAVE_ATOMIC_EXCHANGE_8   IFUNC_COND_1
  88 # undef MAYBE_HAVE_ATOMIC_LDST_8
  89 # define MAYBE_HAVE_ATOMIC_LDST_8       IFUNC_COND_1
  90 # if IFUNC_ALT == 1
  91 #  undef HAVE_ATOMIC_CAS_8
  92 #  define HAVE_ATOMIC_CAS_8 1
  93 # endif
  94 #endif
  95
  96 #if defined(__x86_64__) && N == 16 && IFUNC_ALT == 1
  97 static inline bool
  98 atomic_compare_exchange_n (UTYPE *mptr, UTYPE *eptr, UTYPE newval,
  99                            bool weak_p UNUSED, int sm UNUSED, int fm UNUSED)
 100 {
 101   UTYPE cmpval = *eptr;
 102   UTYPE oldval = __sync_val_compare_and_swap_16 (mptr, cmpval, newval);
 103   if (oldval == cmpval)
 104     return true;
 105   *eptr = oldval;
 106   return false;
 107 }
 108 # define atomic_compare_exchange_n atomic_compare_exchange_n
 109 #endif /* Have CAS 16 */
 110
 111 #endif /* HAVE_IFUNC */
 112
 113 #include_next <host-config.h>