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zfs/include/linux/math64_compat.h

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Add __divdi3(), remove __udivdi3() kernel dependency Up until now no SPL consumer attempted to perform signed 64-bit division so there was no need to support this. That has now changed so I adding 64-bit division support for 32-bit platforms. The signed implementation is based on the unsigned version. Since the have been several bug reports in the past concerning correct 64-bit division on 32-bit platforms I added some long over due regression tests. Much to my surprise the unsigned 64-bit division regression tests failed. This was surprising because __udivdi3() was implemented by simply calling div64_u64() which is provided by the kernel. This meant that the linux kernels 64-bit division algorithm on 32-bit platforms was flawed. After some investigation this turned out to be exactly the case. Because of this I was forced to abandon the kernel helper and instead to fully implement 64-bit division in the spl. There are several published implementation out there on how to do this properly and I settled on one proposed in the book Hacker's Delight. Their proposed algoritm is freely available without restriction and I have just modified it to be linux kernel friendly. The update implementation now passed all the unsigned and signed regression tests. This should be functional, but not fast, which is good enough for out purposes. If you want fast too I'd strongly suggest you upgrade to a 64-bit platform. I have also reported the kernel bug and we'll see if we can't get it fixed up stream.
2010-07-12 19:38:34 +00:00
/*****************************************************************************\
* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
* Copyright (C) 2007 The Regents of the University of California.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
Refresh links to web site Update links to refer to the official ZFS on Linux website instead of @behlendorf's personal fork on github. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2013-03-05 01:26:55 +00:00
* For details, see <http://zfsonlinux.org/>.
Add __divdi3(), remove __udivdi3() kernel dependency Up until now no SPL consumer attempted to perform signed 64-bit division so there was no need to support this. That has now changed so I adding 64-bit division support for 32-bit platforms. The signed implementation is based on the unsigned version. Since the have been several bug reports in the past concerning correct 64-bit division on 32-bit platforms I added some long over due regression tests. Much to my surprise the unsigned 64-bit division regression tests failed. This was surprising because __udivdi3() was implemented by simply calling div64_u64() which is provided by the kernel. This meant that the linux kernels 64-bit division algorithm on 32-bit platforms was flawed. After some investigation this turned out to be exactly the case. Because of this I was forced to abandon the kernel helper and instead to fully implement 64-bit division in the spl. There are several published implementation out there on how to do this properly and I settled on one proposed in the book Hacker's Delight. Their proposed algoritm is freely available without restriction and I have just modified it to be linux kernel friendly. The update implementation now passed all the unsigned and signed regression tests. This should be functional, but not fast, which is good enough for out purposes. If you want fast too I'd strongly suggest you upgrade to a 64-bit platform. I have also reported the kernel bug and we'll see if we can't get it fixed up stream.
2010-07-12 19:38:34 +00:00
*
* The SPL 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 2 of the License, or (at your
* option) any later version.
*
* The SPL 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.
*
* You should have received a copy of the GNU General Public License along
* with the SPL. If not, see <http://www.gnu.org/licenses/>.
\*****************************************************************************/
#ifndef _SPL_MATH64_COMPAT_H
#define _SPL_MATH64_COMPAT_H
#ifndef abs64
#define abs64(x) ({ uint64_t t = (x) >> 63; ((x) ^ t) - t; })
#endif
#endif /* _SPL_MATH64_COMPAT_H */