From: George Anzinger <george@mvista.com>
To: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: Andrew Morton <akpm@osdl.org>,
torvalds@osdl.org, linux-kernel@vger.kernel.org, "Nakajima,
Jun" <jun.nakajima@intel.com>
Subject: Re: [PATCHSET][2.6-test4][0/6]Support for HPET based timer - Take 2
Date: Fri, 05 Sep 2003 15:26:13 -0700 [thread overview]
Message-ID: <3F590D85.20803@mvista.com> (raw)
In-Reply-To: <C8C38546F90ABF408A5961FC01FDBF1902C7D224@fmsmsx405.fm.intel.com>
Pallipadi, Venkatesh wrote:
>
>
>>-----Original Message-----
>>From: Andrew Morton [mailto:akpm@osdl.org]
>>
>>We seem to keep on proliferating home-grown x86 64-bit math functions.
>>
>>Do you really need these? Is it possible to use do_div() and
>>the C 64x64
>>`*' operator instead?
>>
>
>
>
> We can change these handcoded 64 bit divs to do_div, with just an
> additional data copy
We already have this in .../include/asm-i386/div64.h. Check usage in
.../posix-timers.c to cover archs that have not yet included it in
there div64.h.
> (as do_div changes dividend in place). But, changing mul into 64x64 '*'
> may be tricky.
> Gcc seem to generate a combination of mul, 2imul and add, where as we
> are happy with
> using only one mull here.
You just need to do the right casting. It should like
u64=u32*(u64)u32 as in .../kernel/posix-timers.c. This could also be
signed with the same results. If you really need to do a u64*u32, it
will do that as well but takes two mpys. In this case you will need
to do it unsigned to eliminate the third mpy.
>
>
--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
next prev parent reply other threads:[~2003-09-05 22:28 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-29 23:58 [PATCHSET][2.6-test4][0/6]Support for HPET based timer - Take 2 Pallipadi, Venkatesh
2003-09-05 22:26 ` George Anzinger [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-09-06 19:04 Pallipadi, Venkatesh
2003-09-07 17:57 ` George Anzinger
2003-08-30 16:26 Pallipadi, Venkatesh
2003-08-29 16:12 Pallipadi, Venkatesh
2003-08-30 4:59 ` David Mosberger-Tang
[not found] <pEGJ.73p.5@gated-at.bofh.it>
2003-08-29 3:40 ` David Mosberger-Tang
2003-08-28 23:41 Pallipadi, Venkatesh
2003-08-29 18:23 ` Andrew Morton
2003-08-29 21:03 ` Erik Andersen
2003-08-31 21:05 ` Linus Torvalds
2003-08-31 22:24 ` Erik Andersen
2003-08-31 22:48 ` Linus Torvalds
2003-09-05 22:19 ` George Anzinger
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