sysdeps/unix/sysv/linux/arm/atomic-machine.h

   1 /* Atomic operations.  ARM/Linux version.
   2    Copyright (C) 2002-2017 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    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <stdint.h>
  20
  21 /* If the compiler doesn't provide a primitive, we'll use this macro
  22    to get assistance from the kernel.  */
  23 #ifdef __thumb2__
  24 # define __arm_assisted_full_barrier() \
  25      __asm__ __volatile__                                                     \
  26              ("movw\tip, #0x0fa0\n\t"                                         \
  27               "movt\tip, #0xffff\n\t"                                         \
  28               "blx\tip"                                                       \
  29               : : : "ip", "lr", "cc", "memory");
  30 #else
  31 # define __arm_assisted_full_barrier() \
  32      __asm__ __volatile__                                                     \
  33              ("mov\tip, #0xffff0fff\n\t"                                      \
  34               "mov\tlr, pc\n\t"                                               \
  35               "add\tpc, ip, #(0xffff0fa0 - 0xffff0fff)"                       \
  36               : : : "ip", "lr", "cc", "memory");
  37 #endif
  38
  39 /* Atomic compare and exchange.  This sequence relies on the kernel to
  40    provide a compare and exchange operation which is atomic on the
  41    current architecture, either via cleverness on pre-ARMv6 or via
  42    ldrex / strex on ARMv6.
  43
  44    It doesn't matter what register is used for a_oldval2, but we must
  45    specify one to work around GCC PR rtl-optimization/21223.  Otherwise
  46    it may cause a_oldval or a_tmp to be moved to a different register.
  47
  48    We use the union trick rather than simply using __typeof (...) in the
  49    declarations of A_OLDVAL et al because when NEWVAL or OLDVAL is of the
  50    form *PTR and PTR has a 'volatile ... *' type, then __typeof (*PTR) has
  51    a 'volatile ...' type and this triggers -Wvolatile-register-var to
  52    complain about 'register volatile ... asm ("reg")'.  */
  53 #ifdef __thumb2__
  54 /* Thumb-2 has ldrex/strex.  However it does not have barrier instructions,
  55    so we still need to use the kernel helper.  */
  56 # define __arm_assisted_compare_and_exchange_val_32_acq(mem, newval, oldval) \
  57   ({ union { __typeof (oldval) a; uint32_t v; } oldval_arg = { .a = (oldval) };\
  58      union { __typeof (newval) a; uint32_t v; } newval_arg = { .a = (newval) };\
  59      register uint32_t a_oldval asm ("r0");                                   \
  60      register uint32_t a_newval asm ("r1") = newval_arg.v;                    \
  61      register __typeof (mem) a_ptr asm ("r2") = (mem);                        \
  62      register uint32_t a_tmp asm ("r3");                                      \
  63      register uint32_t a_oldval2 asm ("r4") = oldval_arg.v;                   \
  64      __asm__ __volatile__                                                     \
  65              ("0:\tldr\t%[tmp],[%[ptr]]\n\t"                                  \
  66               "cmp\t%[tmp], %[old2]\n\t"                                      \
  67               "bne\t1f\n\t"                                                   \
  68               "mov\t%[old], %[old2]\n\t"                                      \
  69               "movw\t%[tmp], #0x0fc0\n\t"                                     \
  70               "movt\t%[tmp], #0xffff\n\t"                                     \
  71               "blx\t%[tmp]\n\t"                                               \
  72               "bcc\t0b\n\t"                                                   \
  73               "mov\t%[tmp], %[old2]\n\t"                                      \
  74               "1:"                                                            \
  75               : [old] "=&r" (a_oldval), [tmp] "=&r" (a_tmp)                   \
  76               : [new] "r" (a_newval), [ptr] "r" (a_ptr),                      \
  77                 [old2] "r" (a_oldval2)                                        \
  78               : "ip", "lr", "cc", "memory");                                  \
  79      (__typeof (oldval)) a_tmp; })
  80 #else
  81 # define __arm_assisted_compare_and_exchange_val_32_acq(mem, newval, oldval) \
  82   ({ union { __typeof (oldval) a; uint32_t v; } oldval_arg = { .a = (oldval) };\
  83      union { __typeof (newval) a; uint32_t v; } newval_arg = { .a = (newval) };\
  84      register uint32_t a_oldval asm ("r0");                                   \
  85      register uint32_t a_newval asm ("r1") = newval_arg.v;                    \
  86      register __typeof (mem) a_ptr asm ("r2") = (mem);                        \
  87      register uint32_t a_tmp asm ("r3");                                      \
  88      register uint32_t a_oldval2 asm ("r4") = oldval_arg.v;                   \
  89      __asm__ __volatile__                                                     \
  90              ("0:\tldr\t%[tmp],[%[ptr]]\n\t"                                  \
  91               "cmp\t%[tmp], %[old2]\n\t"                                      \
  92               "bne\t1f\n\t"                                                   \
  93               "mov\t%[old], %[old2]\n\t"                                      \
  94               "mov\t%[tmp], #0xffff0fff\n\t"                                  \
  95               "mov\tlr, pc\n\t"                                               \
  96               "add\tpc, %[tmp], #(0xffff0fc0 - 0xffff0fff)\n\t"               \
  97               "bcc\t0b\n\t"                                                   \
  98               "mov\t%[tmp], %[old2]\n\t"                                      \
  99               "1:"                                                            \
 100               : [old] "=&r" (a_oldval), [tmp] "=&r" (a_tmp)                   \
 101               : [new] "r" (a_newval), [ptr] "r" (a_ptr),                      \
 102                 [old2] "r" (a_oldval2)                                        \
 103               : "ip", "lr", "cc", "memory");                                  \
 104      (__typeof (oldval)) a_tmp; })
 105 #endif
 106
 107 #include <sysdeps/arm/atomic-machine.h>