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/* Machine-dependent pthreads configuration and inline functions.

   i386 version.

   Copyright (C) 1996-2001, 2002 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Richard Henderson <rth@tamu.edu>.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public License as

   published by the Free Software Foundation; either version 2.1 of the

   License, or (at your option) any later version.

   The GNU C Library 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; see the file COPYING.LIB.  If not,

   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,

   Boston, MA 02111-1307, USA.  */

#ifndef _PT_MACHINE_H

#define _PT_MACHINE_H   1

#ifndef __ASSEMBLER__

#ifndef PT_EI

# define PT_EI extern inline

#endif

extern long int testandset (int *spinlock);

extern int __compare_and_swap (long int *p, long int oldval, long int newval);

/* Get some notion of the current stack.  Need not be exactly the top

   of the stack, just something somewhere in the current frame.  */

#define CURRENT_STACK_FRAME  __builtin_frame_address (0)

/* See if we can optimize for newer cpus... */

#if defined __GNUC__ && __GNUC__ >= 2 && defined __i486__ || defined __pentium__ || defined __pentiumpro__

/* Spinlock implementation; required.  */

PT_EI long int

testandset (int *spinlock)

{

  long int ret;

  __asm__ __volatile__ (

        "xchgl %0, %1"

        : "=r" (ret), "=m" (*spinlock)

        : "0" (1), "m" (*spinlock)

        : "memory");

  return ret;

}

/* Compare-and-swap for semaphores.  It's always available on i686.  */

#define HAS_COMPARE_AND_SWAP

PT_EI int

__compare_and_swap (long int *p, long int oldval, long int newval)

{

  char ret;

  long int readval;

  __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"

                        : "=q" (ret), "=m" (*p), "=a" (readval)

                        : "r" (newval), "m" (*p), "a" (oldval)

                        : "memory");

  return ret;

}

#if __ASSUME_LDT_WORKS > 0

#include "../useldt.h"

#endif

/* The P4 and above really want some help to prevent overheating.  */

#define BUSY_WAIT_NOP   __asm__ ("rep; nop")

#else /* Generic i386 implementation */

/* Spinlock implementation; required.  */

PT_EI long int

testandset (int *spinlock)

{

  long int ret;

  __asm__ __volatile__(

       "xchgl %0, %1"

       : "=r"(ret), "=m"(*spinlock)

       : "0"(1), "m"(*spinlock)

       : "memory");

  return ret;

}

/* Compare-and-swap for semaphores.

   Available on the 486 and above, but not on the 386.

   We test dynamically whether it's available or not. */

#define HAS_COMPARE_AND_SWAP

#define TEST_FOR_COMPARE_AND_SWAP

PT_EI int

__compare_and_swap (long int *p, long int oldval, long int newval)

{

  char ret;

  long int readval;

  __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"

                        : "=q" (ret), "=m" (*p), "=a" (readval)

                        : "r" (newval), "m" (*p), "a" (oldval)

                        : "memory");

  return ret;

}

PT_EI int

get_eflags (void)

{

  int res;

  __asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );

  return res;

}

PT_EI void

set_eflags (int newflags)

{

  __asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");

}

PT_EI int

compare_and_swap_is_available (void)

{

  int oldflags = get_eflags ();

  int changed;

  /* Flip AC bit in EFLAGS.  */

  set_eflags (oldflags ^ 0x40000);

  /* See if bit changed.  */

  changed = (get_eflags () ^ oldflags) & 0x40000;

  /* Restore EFLAGS.  */

  set_eflags (oldflags);

  /* If the AC flag did not change, it's a 386 and it lacks cmpxchg.

     Otherwise, it's a 486 or above and it has cmpxchg.  */

  return changed != 0;

}

#endif /* Generic i386 implementation */

#endif /* __ASSEMBLER__ */

#endif /* pt-machine.h */