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Re: FP emulation patch available

To: "Harald Koerfgen" <Harald.Koerfgen@home.ivm.de>
Subject: Re: FP emulation patch available
From: "Kevin D. Kissell" <kevink@mips.com>
Date: Sun, 12 Mar 2000 14:03:35 +0100
Cc: "Linux SGI" <linux@cthulhu.engr.sgi.com>, <linux-mips@fnet.fr>, <linux-mips@vger.rutgers.edu>
Sender: owner-linuxmips@oss.sgi.com
>My DS 5000/133 (R3000A) with FPU disabled and FPU emulation shows:
> Illegal instruction 00000034 at 801ce924, ...
>
>System.map shows:
> 801ce920 b dsemul_insns
> 801ce928 b dsemul_cpc
>
>Looks like your trick in mips_dsemul() doesn't work too well for ISA-I CPUs. Do
>you have an idea for an alternative?


I have come up with a slightly-less-pretty hack that uses the
Load Address Error trap instead of the Trap instruction to force
kernel entry in the delay slot emulator. It seems just as functional
as the previous version (i.e. operational but "paranoia" finds an
exponentiation problem), and is currently being tortured with crashme
to see if it holds up under corrupted instruction streams and corrupted
process states.  I attach a pseudo-patch (cvs diff -c output) for the changes
relative to the version obtained by applying the previous patches on the
paralogos.com server, and would appreicate verification that it does
indeed work on an R3K.  If it does, I'll check it into the MIPS repository
and it will be included in the next web distribution (and maybe our
CD-ROMS).

My apologies to those of you whose mailers can't handle
attachments.

            Regards,

            Kevin K.


Attachment: cp1emu.patch
Description: Binary data

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