From: Nigel Stephens <nigel@mips.com>
To: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: Richard Sandiford <rsandifo@redhat.com>,
Ralf Baechle <ralf@linux-mips.org>,
Richard Henderson <rth@redhat.com>,
gcc-patches@gcc.gnu.org, linux-mips@linux-mips.org
Subject: Re: [patch] MIPS/gcc: Revert removal of DImode shifts for 32-bit targets
Date: Thu, 05 Aug 2004 00:39:11 +0100 [thread overview]
Message-ID: <4111739F.8010701@mips.com> (raw)
In-Reply-To: <Pine.LNX.4.58L.0408042239260.11595@blysk.ds.pg.gda.pl>
Maciej W. Rozycki wrote:
>On Wed, 4 Aug 2004, Nigel Stephens wrote:
>
>
>
>>>Here are my proposals I've referred to previously. Instruction counts
>>>are 9, 9 and 10, respectively, as I've missed an additional instruction
>>>required to handle shifts by 0 (or actually any multiples of 64).
>>>
>>>
>>IMHO handling a shift by zero correctly is important.
>>
>>
>
> Agreed, hence an additional instruction needed.
>
>
>
>>> "not %1, %3\n\t"
>>> "srlv %1, %L2, %1\n\t"
>>> "srl %1, %1, 1\n\t"
>>>
>>>
>>>
>>Why not the shorter:
>>
>>
>>
>>> "neg %1, %3\n\t"
>>> "srlv %1, %L2, %1\n\t"
>>>
>>>
>
> Notice the difference -- this shorter code doesn't handle shifts by zero
>correctly. ;-)
>
>
Ah yes, I see. I did it with a conditional move to fix up after the
shift, but same result.
>>And then in __ashrdi3:
>>
>> "andi %1, %3, 0x20\n\t"
>> ".set push\n\t"
>> ".set noat\n\t"
>> "sra $1, %M2, 31\n\t"
>> "movn %L0, %M0, %1\n\t"
>> "movn %M0, $1, %1\n\t"
>> ".set pop"
>>
>>Cute, but I think that should be
>>
>> "sra $1, %M0, 31\n\t"
>>
>>(i.e %M0 not %M2)
>>
>>
>
> Well, I've tested it for all shift counts and it works properly as is --
>we care of the value of bit #31 to be shifted only and at this stage it's
>the same in both registers. So it's just a matter of style.
>
>
>
OK, I see
Nigel
next prev parent reply other threads:[~2004-08-04 23:39 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-19 15:35 [patch] MIPS/gcc: Revert removal of DImode shifts for 32-bit targets Maciej W. Rozycki
2004-07-19 16:59 ` Richard Sandiford
2004-07-19 17:32 ` [patch] MIPS/gcc: Revert removal of DImode shifts for 32-bittargets David Edelsohn
2004-07-19 17:33 ` [patch] MIPS/gcc: Revert removal of DImode shifts for 32-bit targets Maciej W. Rozycki
2004-07-19 17:37 ` Richard Sandiford
2004-07-19 21:38 ` Richard Henderson
2004-07-23 14:41 ` Maciej W. Rozycki
2004-07-23 20:27 ` Richard Henderson
2004-07-23 21:12 ` Ralf Baechle
2004-07-26 11:56 ` Maciej W. Rozycki
2004-08-02 20:03 ` Nigel Stephens
2004-08-03 5:30 ` Richard Sandiford
2004-08-03 9:22 ` Nigel Stephens
2004-08-03 9:36 ` Richard Sandiford
2004-08-03 9:54 ` Nigel Stephens
2004-08-04 19:57 ` Maciej W. Rozycki
2004-08-04 20:37 ` Nigel Stephens
2004-08-04 20:54 ` Maciej W. Rozycki
2004-08-04 23:39 ` Nigel Stephens [this message]
2004-08-07 19:01 ` Richard Sandiford
2004-08-09 22:08 ` Richard Henderson
2004-08-10 5:30 ` Richard Sandiford
2004-08-10 23:20 ` Richard Henderson
2004-08-11 0:24 ` Andreas Schwab
2004-08-11 0:40 ` Paul Brook
2004-08-11 4:32 ` Richard Henderson
2004-08-31 19:51 ` Richard Sandiford
2004-09-03 6:53 ` Richard Henderson
2004-09-03 7:05 ` Richard Sandiford
2004-09-03 7:08 ` Richard Henderson
2004-09-03 7:11 ` Richard Sandiford
2004-09-03 7:20 ` Richard Henderson
2004-09-03 7:29 ` Richard Sandiford
2004-09-03 20:15 ` Richard Henderson
2004-09-04 8:53 ` Richard Sandiford
2004-09-05 0:03 ` Richard Henderson
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=4111739F.8010701@mips.com \
--to=nigel@mips.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=linux-mips@linux-mips.org \
--cc=macro@linux-mips.org \
--cc=ralf@linux-mips.org \
--cc=rsandifo@redhat.com \
--cc=rth@redhat.com \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox