From: hjl@nynexst.com (H.J. Lu)
To: meissner@osf.org (Michael Meissner)
Cc: gas2@cygnus.com
Subject: Re: An old gas bug
Date: Wed, 17 Aug 1994 06:16:00 -0000 [thread overview]
Message-ID: <9408171315.AA23850@titanic.nynexst.com> (raw)
In-Reply-To: <9408171307.AA00342@pasta.osf.org>
>
> | Hi,
> |
> | This is a very old bug date back to 1.38.1. The reason no one really
> | cares is gcc won't generate that kind of code, i.e., jump out of range.
> | When some Linux people were working on X11R5, they used an Intel x86
> | branch/loop instruction, jcxz, which has only byte displacements in
> | the hand coded asm code. The AT&T as worked fine with expansion. But
> | gas 1.38.1 generated some bogus codes. I fixed the bug for them. I
> | think it is correct. The test case is very easy to produce. Please let
> | me know if you need one.
>
> While it should be certainly fixed in the assembler, the X11 code
> should also replace the jcxz instruction with a compare against 0 and
> jmp sequence, since that is faster on anything but an original 386.
> See the optimization guides in the 486/pentium manuals.
>
>
After I told them that, they have then changed the code.
--
H.J. Lu
NYNEX Science and Technology, Inc. hjl@nynexst.com
next prev parent reply other threads:[~1994-08-17 6:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
1994-08-16 16:04 H.J. Lu
1994-08-17 6:08 ` Michael Meissner
1994-08-17 6:16 ` H.J. Lu [this message]
[not found] <199408171947.PAA12811@sanguine.cygnus.com>
1994-08-17 14:36 ` H.J. Lu
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