From: "H. Peter Anvin" <hpa@zytor.com>
To: Rask Ingemann Lambertsen <rask@sygehus.dk>
Cc: Uros Bizjak <ubizjak@gmail.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Jan Hubicka <jh@suse.cz>,
Richard Kenner <kenner@vlsi1.ultra.nyu.edu>,
rridge@csclub.uwaterloo.ca
Subject: Re: New back end ia16: 16-bit Intel x86
Date: Sun, 19 Aug 2007 20:07:00 -0000 [thread overview]
Message-ID: <46C8A0C8.4020309@zytor.com> (raw)
In-Reply-To: <20070819105617.GB25795@sygehus.dk>
Rask Ingemann Lambertsen wrote:
>
>>>> It is also much harder to eliminate the frame pointer in
>>>> 16-bit mode, since there is no %sp-based addressing at all.
>>> With disp(%esp) being valid on i386, you don't have that problem either.
>> If your environment isn't clean w.r.t. the top half of %esp, you can't
>> *ever* use this mode. The stack pointer especially...
>
> It doesn't seem to be a likely problem to me. Code operating on %sp can't
> clobber the top half[1]. Code operating on %esp will need to restore it or run
> into trouble. It would be very unusual to not restore the stack pointer. If
> this was to be a problem, you wouldn't be able to just use ".code16gcc".
>
It would be a bug, to be sure, and as I said, I haven't actually seen it
"in the wild" which is a good thing. Given the kind of crap I've seen
BIOS vendors do, though, I can't rule it out.
> [1] Strictly speaking, only bits 16-19 are of any concern.
Uh, no. Any bits [31:16] set will cause a segment violation.
-hpa
next prev parent reply other threads:[~2007-08-19 19:58 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-06 14:23 Uros Bizjak
2007-08-07 1:29 ` Rask Ingemann Lambertsen
2007-08-07 17:37 ` Daniel Jacobowitz
2007-08-07 20:03 ` Uros Bizjak
2007-08-08 12:21 ` Jan Hubicka
2007-08-08 17:30 ` Mark Mitchell
2007-08-08 23:22 ` Richard Kenner
2007-08-08 18:52 ` Rask Ingemann Lambertsen
2007-08-08 20:24 ` Michael Matz
2007-08-08 20:59 ` H.J. Lu
2007-08-08 22:46 ` DJ Delorie
2007-08-09 9:33 ` Jan Hubicka
2007-08-09 14:01 ` Rask Ingemann Lambertsen
2007-08-09 15:43 ` DJ Delorie
2007-08-08 15:28 ` Rask Ingemann Lambertsen
2007-08-17 22:38 ` H. Peter Anvin
2007-08-18 2:34 ` Rask Ingemann Lambertsen
2007-08-18 5:33 ` H. Peter Anvin
2007-08-18 17:36 ` Rask Ingemann Lambertsen
2007-08-18 17:50 ` H. Peter Anvin
2007-08-18 20:39 ` Rask Ingemann Lambertsen
2007-08-19 2:11 ` H. Peter Anvin
2007-08-19 12:25 ` Rask Ingemann Lambertsen
2007-08-19 20:07 ` H. Peter Anvin [this message]
2007-08-21 8:48 ` H. Peter Anvin
2007-08-21 14:35 ` Rask Ingemann Lambertsen
2007-08-21 17:46 ` H. Peter Anvin
2007-08-21 18:56 ` Real-mode i386 back end (Was: New back end ia16: 16-bit Intel x86) Rask Ingemann Lambertsen
2007-08-19 7:29 ` New back end ia16: 16-bit Intel x86 H. Peter Anvin
2007-08-19 10:56 ` Rask Ingemann Lambertsen
2007-08-19 21:40 ` H. Peter Anvin
-- strict thread matches above, loose matches on Subject: below --
2007-08-19 19:58 Ross Ridge
2007-08-19 16:11 Ross Ridge
2007-08-19 17:36 ` Rask Ingemann Lambertsen
2007-08-18 20:46 Ross Ridge
2007-08-19 16:20 ` Rask Ingemann Lambertsen
2007-08-02 20:15 Ross Ridge
2007-08-01 19:25 Ross Ridge
2007-08-01 22:57 ` Rask Ingemann Lambertsen
[not found] <20070801153758.ACBB974253@caffeine.csclub.uwaterloo.ca.suse.lists.egcs-patches>
2007-08-01 17:44 ` Andi Kleen
2007-08-01 15:38 Ross Ridge
2007-08-01 17:59 ` Rask Ingemann Lambertsen
2007-07-31 18:06 Ross Ridge
2007-08-01 0:34 ` Rask Ingemann Lambertsen
2007-08-01 9:53 ` Richard Kenner
2007-08-01 12:33 ` Rask Ingemann Lambertsen
2007-08-01 12:44 ` Richard Kenner
2007-08-01 13:41 ` Rask Ingemann Lambertsen
2007-08-01 13:52 ` Richard Kenner
2007-08-01 10:38 ` Jan Hubicka
2007-08-01 17:30 ` Rask Ingemann Lambertsen
2007-07-31 15:24 Ross Ridge
2007-07-31 17:44 ` Michael Matz
2007-07-31 0:50 Ross Ridge
2007-07-31 8:54 ` Tristan Gingold
2007-07-31 13:46 ` Rask Ingemann Lambertsen
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