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/*
* ptw32_InterlockedCompareExchange.c
*
* Description:
* This translation unit implements routines which are private to
* the implementation and may be used throughout it.
*
* --------------------------------------------------------------------------
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999,2005 Pthreads-win32 contributors
*
* Contact Email: rpj@callisto.canberra.edu.au
*
* The current list of contributors is contained
* in the file CONTRIBUTORS included with the source
* code distribution. The list can also be seen at the
* following World Wide Web location:
* http://sources.redhat.com/pthreads-win32/contributors.html
*
* This 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 of the License, or (at your option) any later version.
*
* This 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 this library in the file COPYING.LIB;
* if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if 0
#ifndef _WIN64
#include "pthread.h"
#include "implement.h"
/*
* ptw32_InterlockedCompareExchange --
*
* Originally needed because W9x doesn't support InterlockedCompareExchange.
* We now use this version wherever possible so we can inline it.
*/
PTW32_INTERLOCKED_LONG WINAPI
ptw32_InterlockedCompareExchange (PTW32_INTERLOCKED_LPLONG location,
PTW32_INTERLOCKED_LONG value,
PTW32_INTERLOCKED_LONG comparand)
{
#if defined(__WATCOMC__)
/* Don't report that result is not assigned a value before being referenced */
#pragma disable_message (200)
#endif
PTW32_INTERLOCKED_LONG result;
/*
* Using the LOCK prefix on uni-processor machines is significantly slower
* and it is not necessary. The overhead of the conditional below is
* negligible in comparison. Since an optimised DLL will inline this
* routine, this will be faster than calling the system supplied
* Interlocked routine, which appears to avoid the LOCK prefix on
* uniprocessor systems. So one DLL works for all systems.
*/
if (ptw32_smp_system)
/* *INDENT-OFF* */
#if defined(_M_IX86) || defined(_X86_)
#if defined(_MSC_VER) || defined(__WATCOMC__) || (defined(__BORLANDC__) && defined(HAVE_TASM32))
#define HAVE_INLINABLE_INTERLOCKED_CMPXCHG
{
_asm {
PUSH ecx
PUSH edx
MOV ecx,dword ptr [location]
MOV edx,dword ptr [value]
MOV eax,dword ptr [comparand]
LOCK CMPXCHG dword ptr [ecx],edx
MOV dword ptr [result], eax
POP edx
POP ecx
}
}
else
{
_asm {
PUSH ecx
PUSH edx
MOV ecx,dword ptr [location]
MOV edx,dword ptr [value]
MOV eax,dword ptr [comparand]
CMPXCHG dword ptr [ecx],edx
MOV dword ptr [result], eax
POP edx
POP ecx
}
}
#elif defined(__GNUC__)
#define HAVE_INLINABLE_INTERLOCKED_CMPXCHG
{
__asm__ __volatile__
(
"lock\n\t"
"cmpxchgl %2,%1" /* if (EAX == [location]) */
/* [location] = value */
/* else */
/* EAX = [location] */
:"=a" (result)
:"m" (*location), "r" (value), "a" (comparand));
}
else
{
__asm__ __volatile__
(
"cmpxchgl %2,%1" /* if (EAX == [location]) */
/* [location] = value */
/* else */
/* EAX = [location] */
:"=a" (result)
:"m" (*location), "r" (value), "a" (comparand));
}
#endif
#else
/*
* If execution gets to here then we're running on a currently
* unsupported processor or compiler.
*/
#error Unsupported platform or compiler!
#endif
/* *INDENT-ON* */
return result;
#if defined(__WATCOMC__)
#pragma enable_message (200)
#endif
}
#if 0
/*
* ptw32_InterlockedExchange --
*
* We now use this version wherever possible so we can inline it.
*/
LONG WINAPI
ptw32_InterlockedExchange (LPLONG location,
LONG value)
{
#if defined(__WATCOMC__)
/* Don't report that result is not assigned a value before being referenced */
#pragma disable_message (200)
#endif
LONG result;
/*
* The XCHG instruction always locks the bus with or without the
* LOCKED prefix. This makes it significantly slower than CMPXCHG on
* uni-processor machines. The Windows InterlockedExchange function
* is nearly 3 times faster than the XCHG instruction, so this routine
* is not yet very useful for speeding up pthreads.
*/
if (ptw32_smp_system)
/* *INDENT-OFF* */
#if defined(_M_IX86) || defined(_X86_)
#if defined(_MSC_VER) || defined(__WATCOMC__) || (defined(__BORLANDC__) && defined(HAVE_TASM32))
#define HAVE_INLINABLE_INTERLOCKED_XCHG
{
_asm {
PUSH ecx
MOV ecx,dword ptr [location]
MOV eax,dword ptr [value]
XCHG dword ptr [ecx],eax
MOV dword ptr [result], eax
POP ecx
}
}
else
{
/*
* Faster version of XCHG for uni-processor systems because
* it doesn't lock the bus. If an interrupt or context switch
* occurs between the MOV and the CMPXCHG then the value in
* 'location' may have changed, in which case we will loop
* back to do the MOV again.
*
* Tests show that this routine has almost identical timing
* to Win32's InterlockedExchange(), which is much faster than
* using the inlined 'xchg' instruction above, so it's probably
* doing something similar to this (on UP systems).
*
* Can we do without the PUSH/POP instructions?
*/
_asm {
PUSH ecx
PUSH edx
MOV ecx,dword ptr [location]
MOV edx,dword ptr [value]
L1: MOV eax,dword ptr [ecx]
CMPXCHG dword ptr [ecx],edx
JNZ L1
MOV dword ptr [result], eax
POP edx
POP ecx
}
}
#elif defined(__GNUC__)
#define HAVE_INLINABLE_INTERLOCKED_XCHG
{
__asm__ __volatile__
(
"xchgl %2,%1"
:"=r" (result)
:"m" (*location), "0" (value));
}
else
{
/*
* Faster version of XCHG for uni-processor systems because
* it doesn't lock the bus. If an interrupt or context switch
* occurs between the movl and the cmpxchgl then the value in
* 'location' may have changed, in which case we will loop
* back to do the movl again.
*
* Tests show that this routine has almost identical timing
* to Win32's InterlockedExchange(), and is much faster than
* using an inlined 'xchg' instruction, so Win32 is probably
* doing something similar to this (on UP systems).
*/
__asm__ __volatile__
(
"0:\n\t"
"movl %1,%%eax\n\t"
"cmpxchgl %2,%1\n\t"
"jnz 0b"
:"=&a" (result)
:"m" (*location), "r" (value));
}
#endif
#else
/*
* If execution gets to here then we're running on a currently
* unsupported processor or compiler.
*/
#error Unsupported platform or compiler!
#endif
/* *INDENT-ON* */
return result;
#if defined(__WATCOMC__)
#pragma enable_message (200)
#endif
}
#endif
#if 1
#if defined(PTW32_BUILD_INLINED) && defined(HAVE_INLINABLE_INTERLOCKED_CMPXCHG)
#undef PTW32_INTERLOCKED_COMPARE_EXCHANGE
#define PTW32_INTERLOCKED_COMPARE_EXCHANGE ptw32_InterlockedCompareExchange
#endif
#if 0
#if defined(PTW32_BUILD_INLINED) && defined(HAVE_INLINABLE_INTERLOCKED_XCHG)
#undef PTW32_INTERLOCKED_EXCHANGE
#define PTW32_INTERLOCKED_EXCHANGE ptw32_InterlockedExchange
#endif
#endif
#endif
#endif
#endif /* 0 */