libgcc/config/gcn/atomic.c

/* AMD GCN atomic operations
   Copyright (C) 2020-2023 Free Software Foundation, Inc.
   Contributed by Mentor Graphics.

   This file is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by the
   Free Software Foundation; either version 3, or (at your option) any
   later version.

   This file is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   Under Section 7 of GPL version 3, you are granted additional
   permissions described in the GCC Runtime Library Exception, version
   3.1, as published by the Free Software Foundation.

   You should have received a copy of the GNU General Public License and
   a copy of the GCC Runtime Library Exception along with this program;
   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
   <http://www.gnu.org/licenses/>.  */

#include <stdbool.h>

#define __SYNC_SUBWORD_COMPARE_AND_SWAP(TYPE, SIZE)			     \
									     \
TYPE									     \
__sync_val_compare_and_swap_##SIZE (TYPE *ptr, TYPE oldval, TYPE newval)     \
{									     \
  unsigned int valmask = (1 << (SIZE * 8)) - 1;				     \
  unsigned int *wordptr = (unsigned int *)((__UINTPTR_TYPE__ ) ptr & ~3UL);  \
  int shift = ((__UINTPTR_TYPE__ ) ptr & 3UL) * 8;			     \
  unsigned int wordmask = ~(valmask << shift);				     \
  unsigned int oldword = *wordptr;					     \
  for (;;)								     \
    {									     \
      TYPE prevval = (oldword >> shift) & valmask;			     \
      if (__builtin_expect (prevval != oldval, 0))			     \
	return prevval;							     \
      unsigned int newword = oldword & wordmask;			     \
      newword |= ((unsigned int) newval) << shift;			     \
      unsigned int prevword						     \
	  = __sync_val_compare_and_swap_4 (wordptr, oldword, newword);	     \
      if (__builtin_expect (prevword == oldword, 1))			     \
	return oldval;							     \
      oldword = prevword;						     \
    }									     \
}									     \
									     \
bool									     \
__sync_bool_compare_and_swap_##SIZE (TYPE *ptr, TYPE oldval, TYPE newval)    \
{									     \
  return __sync_val_compare_and_swap_##SIZE (ptr, oldval, newval) == oldval; \
}

__SYNC_SUBWORD_COMPARE_AND_SWAP (unsigned char, 1)
__SYNC_SUBWORD_COMPARE_AND_SWAP (unsigned short, 2)


#define __ATOMIC_COMPARE_EXCHANGE(TYPE,SIZE)				      \
bool									      \
__atomic_compare_exchange_##SIZE (TYPE *ptr, TYPE *expected,		      \
				  TYPE desired, bool weak,		      \
				  int success_memorder, int failure_memorder) \
{									      \
  unsigned int valmask = (1 << (SIZE * 8)) - 1;				      \
									      \
  unsigned int *wordptr = (unsigned int *)((__UINTPTR_TYPE__ ) ptr & ~3UL);   \
  int ptrshift = ((__UINTPTR_TYPE__ ) ptr & 3UL) * 8;			      \
  unsigned int wordmask = ~(valmask << ptrshift);			      \
									      \
  unsigned int ptrword = *wordptr;					      \
  unsigned int exptword = ptrword & wordmask;				      \
  unsigned int newword = ptrword & wordmask;				      \
  exptword |= ((unsigned int) *expected) << ptrshift;			      \
  newword |= ((unsigned int) desired) << ptrshift;			      \
  if (__atomic_compare_exchange_4 (wordptr, &exptword, newword, weak,	      \
				   success_memorder, failure_memorder))	      \
    return true;							      \
  *expected = (TYPE) ((exptword >> ptrshift) & valmask);		      \
  return false;								      \
}

__ATOMIC_COMPARE_EXCHANGE (unsigned char, 1)
__ATOMIC_COMPARE_EXCHANGE (unsigned short, 2)