1 /* locks.h - Thread synchronization primitives. X86/x86-64 implementation.
3 Copyright (C) 2002 Free Software Foundation
5 Contributed by Bo Thorsen <bo@suse.de>.
7 This file is part of libgcj.
9 This software is copyrighted work licensed under the terms of the
10 Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
13 #ifndef __SYSDEP_LOCKS_H__
14 #define __SYSDEP_LOCKS_H__
16 typedef size_t obj_addr_t; /* Integer type big enough for object */
19 // Atomically replace *addr by new_val if it was initially equal to old.
20 // Return true if the comparison succeeded.
21 // Assumed to have acquire semantics, i.e. later memory operations
22 // cannot execute before the compare_and_swap finishes.
24 compare_and_swap(volatile obj_addr_t *addr,
30 __asm__ __volatile__("lock; cmpxchgq %2, %0; setz %1"
31 : "=m"(*(addr)), "=q"(result)
32 : "r" (new_val), "a"(old), "m"(*addr)
35 __asm__ __volatile__("lock; cmpxchgl %2, %0; setz %1"
36 : "=m"(*addr), "=q"(result)
37 : "r" (new_val), "a"(old), "m"(*addr)
43 // Set *addr to new_val with release semantics, i.e. making sure
44 // that prior loads and stores complete before this
46 // On X86/x86-64, the hardware shouldn't reorder reads and writes,
47 // so we just have to convince gcc not to do it either.
49 release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
51 __asm__ __volatile__(" " : : : "memory");
55 // Compare_and_swap with release semantics instead of acquire semantics.
56 // On many architecture, the operation makes both guarantees, so the
57 // implementation can be the same.
59 compare_and_swap_release(volatile obj_addr_t *addr,
63 return compare_and_swap(addr, old, new_val);
66 // Ensure that subsequent instructions do not execute on stale
67 // data that was loaded from memory before the barrier.
68 // On X86/x86-64, the hardware ensures that reads are properly ordered.
74 // Ensure that prior stores to memory are completed with respect to other
79 /* x86-64/X86 does not reorder writes. We just need to ensure that
81 __asm__ __volatile__(" " : : : "memory");