From: Konrad Eisele <konrad@gaisler.com>
To: sparclinux@vger.kernel.org
Subject: Re: [PATCH 3/4] sparc32: return destination pointer on return from
Date: Thu, 20 Oct 2011 06:59:15 +0000 [thread overview]
Message-ID: <4E9FC6C3.7040905@gaisler.com> (raw)
In-Reply-To: <1318489205-315-4-git-send-email-konrad@gaisler.com>
David Miller wrote:
> From: Kjetil Oftedal <oftedal@gmail.com>
> Date: Wed, 19 Oct 2011 23:11:29 +0200 (CEST)
>
>> On Wed, 19 Oct 2011, David Miller wrote:
>>
>>> From: Konrad Eisele <konrad@gaisler.com>
>>> Date: Wed, 19 Oct 2011 10:33:25 +0200
>>>
>>>> It seems to me that memcpy is tightly programmed. Is saving 2 lines of gdbstub.c
>>>> diff worth a memcpy rewrite?
>>>
>>> You really can't find another register to save the initial %o0 value in?
>>> Have you even tried?
>>
>> This might be considered a ugly hack. But what about using %y ? According
>> to the V8 manual, %y might be destroyed across a procedure call, and none
>> of the functions in memcpy.S use multiply/divide instructions. It is
>> however not mentioned as a available register in the section dealing with
>> leaf procedures.
>>
>> A quick test on a SS20 did not reveal any immediate side-effects, and
>> the return value of memcpy is now the destination pointer.
>
> Never mind, I'll work on this myself. Trying to get you to implement
> this properly is hopeless. Writing to and reading from the %y
> register is extremely expensive compared to a regular register.
>
>
Sorry to make you angry but, yes, I looked weather all registers are taken,
and yes, memcpy is very compact programmed. The %g6 patch was a mistake, sorry.
-- Konrad
next prev parent reply other threads:[~2011-10-20 6:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-13 7:00 [PATCH 3/4] sparc32: return destination pointer on return from memcpy Konrad Eisele
2011-10-19 4:07 ` [PATCH 3/4] sparc32: return destination pointer on return from David Miller
2011-10-19 8:33 ` Konrad Eisele
2011-10-19 19:29 ` David Miller
2011-10-19 21:11 ` Kjetil Oftedal
2011-10-19 22:12 ` David Miller
2011-10-20 6:59 ` Konrad Eisele [this message]
2011-10-20 8:47 ` David Miller
2011-10-20 9:08 ` Konrad Eisele
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4E9FC6C3.7040905@gaisler.com \
--to=konrad@gaisler.com \
--cc=sparclinux@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.