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- /* 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)
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