From: Doug Evans <dje@sebabeach.org>
To: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: cgen@sources.redhat.com
Subject: Re: branch insn question
Date: Mon, 11 Jan 2010 07:53:00 -0000 [thread overview]
Message-ID: <4B4AD8EC.8000106@sebabeach.org> (raw)
In-Reply-To: <20100109164523.GA15551@doriath.ww600.siemens.net>
Dmitry Eremin-Solenikov wrote:
> Hello,
>
> I've a small problem with branch instructions on my platorm (m68hc08).
> All branch instructions are only short-ranged (signed 8bit offset).
> The recommended way to handle this is to emit jump-over code: instead of
> beq _long_label
> emit:
> bne .Lshort
> jmp _long_label
> .Lshort:
>
> My question is: should this be handled somehow by cgen? Or this should
> be completely done via gas relaxation? And what attributes should I use
> on branch instructions in .cpu file?
>
> Thank you.
>
>
My first thought is that this should be handled at a higher layer than cgen.
OTOH, I can't quite disagree with adding macro-insns that implement
jump-overs.
[Alas, macro insns at the moment are limited to simple 1->1 translations
at the moment so that won't work; I need to add support for
multiple-insn macros, I wouldn't wait for them for this though.]
As for how to handle this in gas, I think the standard
copy-existing-port-and-cut-n-paste-n-tweak will work here. Having not
looked at gas relax support in awhile I just grepped for "relax" in the
gas sources and found several promising starting points. E.g. grep for
TC_GENERIC_RELAX_TABLE.
prev parent reply other threads:[~2010-01-11 7:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-09 16:46 Dmitry Eremin-Solenikov
2010-01-11 7:53 ` Doug Evans [this message]
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