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Re: [PATCH]: R10000 Needs LL/SC Workaround in Gcc
- From: "Maciej W. Rozycki" <macro at linux-mips dot org>
- To: Richard Sandiford <rdsandiford at googlemail dot com>
- Cc: Kumba <kumba at gentoo dot org>, Ralf Baechle <ralf at linux-mips dot org>, gcc-patches at gcc dot gnu dot org, Linux MIPS List <linux-mips at linux-mips dot org>
- Date: Sat, 1 Nov 2008 20:33:03 +0000 (GMT)
- Subject: Re: [PATCH]: R10000 Needs LL/SC Workaround in Gcc
- References: <490A90F4.6040601@gentoo.org> <490C05A9.9070707@gentoo.org> <87abcjibsl.fsf@firetop.home>
On Sat, 1 Nov 2008, Richard Sandiford wrote:
> There are two ways we could handle this:
>
> - Make -mfix-r10000 require -mbranch-likely. (It mustn't _imply_
> -mbranch-likely. It should simply check that -mbranch-likely is
> already in effect.)
>
> - Make -mfix-r10000 insert nops when -mbranch-likely is not in effect.
If I recall right, these is something special about the pipeline in this
context making the branch-likely instructions the only ones that work.
Which would make the option you proposed first the only viable. I am not
absolutely sure and I have no reference handy. Perhaps Ralf or someone at
linux-mips will know?
Maciej