1 /* Machine-dependent pthreads configuration and inline functions.
3 Copyright (C) 1996-2001, 2002, 2003 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5 Contributed by Richard Henderson <rth@tamu.edu>.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public License as
9 published by the Free Software Foundation; either version 2.1 of the
10 License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; see the file COPYING.LIB. If
19 not, see <http://www.gnu.org/licenses/>. */
22 #define _PT_MACHINE_H 1
28 # define PT_EI __extern_always_inline __attribute__((visibility("hidden")))
31 extern long int testandset (int *spinlock);
32 extern int __compare_and_swap (long int *p, long int oldval, long int newval);
34 /* Get some notion of the current stack. Need not be exactly the top
35 of the stack, just something somewhere in the current frame. */
36 #define CURRENT_STACK_FRAME __builtin_frame_address (0)
39 /* See if we can optimize for newer cpus... */
40 #if defined __GNUC__ && __GNUC__ >= 2 && \
41 (defined __i486__ || defined __pentium__ || defined __pentiumpro__ || defined __pentium4__ || \
42 defined __athlon__ || defined __k8__)
44 /* Spinlock implementation; required. */
46 testandset (int *spinlock)
50 __asm__ __volatile__ (
52 : "=r" (ret), "=m" (*spinlock)
53 : "0" (1), "m" (*spinlock)
59 /* Compare-and-swap for semaphores. It's always available on i686. */
60 #define HAS_COMPARE_AND_SWAP
63 __compare_and_swap (long int *p, long int oldval, long int newval)
68 __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
69 : "=q" (ret), "=m" (*p), "=a" (readval)
70 : "r" (newval), "m" (*p), "a" (oldval)
75 #if defined(__ASSUME_LDT_WORKS) && __ASSUME_LDT_WORKS > 0
79 /* The P4 and above really want some help to prevent overheating. */
80 #define BUSY_WAIT_NOP __asm__ ("rep; nop")
83 #else /* Generic i386 implementation */
85 extern int compare_and_swap_is_available (void);
87 /* Spinlock implementation; required. */
89 testandset (int *spinlock)
95 : "=r"(ret), "=m"(*spinlock)
96 : "0"(1), "m"(*spinlock)
103 /* Compare-and-swap for semaphores.
104 Available on the 486 and above, but not on the 386.
105 We test dynamically whether it's available or not. */
107 #define HAS_COMPARE_AND_SWAP
108 #define TEST_FOR_COMPARE_AND_SWAP
111 __compare_and_swap (long int *p, long int oldval, long int newval)
116 __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
117 : "=q" (ret), "=m" (*p), "=a" (readval)
118 : "r" (newval), "m" (*p), "a" (oldval)
124 compare_and_swap_is_available (void)
129 __asm__ __volatile__ ("pushfl; popl %0" : "=r" (oldflags) : );
130 /* Flip AC bit in EFLAGS. */
131 __asm__ __volatile__ ("pushl %0; popfl" : : "r" (oldflags ^ 0x40000) : "cc");
133 __asm__ __volatile__ ("pushfl; popl %0" : "=r" (changed) : );
134 /* See if bit changed. */
135 changed = (changed ^ oldflags) & 0x40000;
136 /* Restore EFLAGS. */
137 __asm__ __volatile__ ("pushl %0; popfl" : : "r" (oldflags) : "cc");
138 /* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
139 Otherwise, it's a 486 or above and it has cmpxchg. */
142 #endif /* Generic i386 implementation */
144 #endif /* __ASSEMBLER__ */
146 #endif /* pt-machine.h */