| /* NVPTX atomic operations |
| Copyright (C) 2020-2022 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> |
| |
| /* Implement __sync_val_compare_and_swap and __sync_bool_compare_and_swap |
| for 1 and 2-byte values (which are not natively supported) in terms of |
| __sync_val_compare_and_swap for 4-byte values (which is supported). |
| This assumes that the contents of the word surrounding the subword |
| value that we are interested in are accessible as well (which should |
| normally be the case). Note that if the contents of the word surrounding |
| the subword changes between the __sync_val_compare_and_swap_4 and the |
| preceeding load of oldword, while the subword does not, the implementation |
| loops, which may manifest worst-case as a hang. */ |
| |
| #define __SYNC_SUBWORD_COMPARE_AND_SWAP(TYPE, SIZE) \ |
| \ |
| TYPE \ |
| __sync_val_compare_and_swap_##SIZE (volatile void *vptr, TYPE oldval, \ |
| TYPE newval) \ |
| { \ |
| volatile TYPE *ptr = vptr; \ |
| volatile unsigned int *wordptr \ |
| = (volatile unsigned int *)((__UINTPTR_TYPE__) ptr & ~3UL); \ |
| int shift = ((__UINTPTR_TYPE__) ptr & 3UL) * 8; \ |
| unsigned int valmask = (1 << (SIZE * 8)) - 1; \ |
| unsigned int wordmask = ~(valmask << shift); \ |
| unsigned int oldword = *wordptr; \ |
| for (;;) \ |
| { \ |
| TYPE prevval = (oldword >> shift) & valmask; \ |
| /* Exit if the subword value previously read from memory is not */ \ |
| /* equal to the expected value OLDVAL. */ \ |
| 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); \ |
| /* Exit only if the compare-and-swap succeeds on the whole word */ \ |
| /* (i.e. the contents of *WORDPTR have not changed since the last */ \ |
| /* memory read). */ \ |
| if (__builtin_expect (prevword == oldword, 1)) \ |
| return oldval; \ |
| oldword = prevword; \ |
| } \ |
| } \ |
| \ |
| bool \ |
| __sync_bool_compare_and_swap_##SIZE (volatile void *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) |