linux-kernel - Re: powerpc/e500: binutils tests [Was: RFC: x86: kill binutils 2.16.x?]

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Message-ID: <20110309072748.GA4773@Chamillionaire.breakpoint.cc>
Date:	Wed, 9 Mar 2011 08:27:48 +0100
From:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
To:	Kyle Moffett <kyle@...fetthome.net>
Cc:	Segher Boessenkool <segher@...nel.crashing.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kbuild <linux-kbuild@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linuxppc-dev@...ts.ozlabs.org,
	Kyle Moffett <kyle.d.moffett@...ing.com>,
	Kumar Gala <kumar.gala@...escale.com>, sebastian@...akpoint.cc
Subject: Re: powerpc/e500: binutils tests [Was: RFC: x86: kill binutils
 2.16.x?]

* Kyle Moffett | 2011-03-09 00:22:11 [-0500]:

>On Tue, Mar 8, 2011 at 23:39, Segher Boessenkool
><segher@...nel.crashing.org> wrote:
>>> The problem is not with the kernel compile itself, but with the 2.12
>>> "dssall" binutils test. ??Basically, recent binutils treats e500 as
>>> effectively a separate architecture that happens to share *most* of
>>> the opcodes with regular PowerPC. ??Any opcode which is not understood
>>> by the e500 chip is either convert to an equivalent opcode which is
>>> understood (IE: lwsync => sync), or failed with an error. ??This means
>>> that the kernel compile aborts early telling me to upgrade to a newer
>>> version of binutils.
>>
>> $ echo dssall | powerpc-linux-as -many -me500
>> $ powerpc-linux-objdump -d a.out | grep 0:
>> ?? 0: ?? 7e 00 06 6c ?? ?? dssall
>> $ powerpc-linux-as --version | head -1
>> GNU assembler (GNU Binutils) 2.21.51.20110309
>>
>> What version of binutils does not work? ??(I also checked with
>> -me500x2, -me500mc, -mspe, and various combinations. ??lwsync
>> is indeed converted to a regular sync (well, "msync") for e500
>> and e500x2).
>
>Hmm, something's fishy here.

Did I break anything?
Not sure if mc and x2 are the same thing. One of those e500 thingy has a
the "classic FPU" if I remember correctly.
Anyway, -me500 enables a certain range of opcodes -many enables all of
them (or the remaining few). So without -many this test will fail. The
auto conversion of lwsync => sync or msync should be performed due to
-me500.

>Just going based on this changeset, the floating point and AltiVec
>opcodes are *supposed* to generate hard errors:
>  http://sourceware.org/ml/binutils-cvs/2010-06/msg00070.html
>
>Oh... that patch only disables the opcodes if "-many" is not specified.

To some degree yes. If you specify -me500 -maltivec you can still use
AltiVec opcodes because you enabled them. So for that reason there are
scripts on buildds to prevent passing mcpu to gcc among other things :)

>Cheers,
>Kyle Moffett

Sebastian
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