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Date: Thu, 31 Oct 2002 07:33:01 -0700
From: Tom Rini <trini@kernel.crashing.org>
To: Mark Mielke <mark@mark.mielke.cc>
Cc: Adrian Bunk <bunk@fs.tum.de>, Rasmus Andersen <rasmus@jaquet.dk>,
       linux-kernel@vger.kernel.org
Subject: Re: CONFIG_TINY
Message-ID: <20021031143301.GC28191@opus.bloom.county>
References: <20021030233605.A32411@jaquet.dk> <Pine.NEB.4.44.0210310145300.20835-100000@mimas.fachschaften.tu-muenchen.de> <20021031011002.GB28191@opus.bloom.county> <20021031053310.GB4780@mark.mielke.cc>
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On Thu, Oct 31, 2002 at 12:33:10AM -0500, Mark Mielke wrote:
> On Wed, Oct 30, 2002 at 06:10:02PM -0700, Tom Rini wrote:
> > On Thu, Oct 31, 2002 at 01:53:14AM +0100, Adrian Bunk wrote:
> > > could you try to use "-Os" instead of "-O2" as gcc optimization option
> > > when CONFIG_TINY is enabled? Something like the following (completely
> > > untested) patch:
> > -Os can produce larger binaries, keep in mind.  If we're going to go
> > this route, how about something generally useful, and allow for general
> > optimization level / additional CFLAGS to be added.
> 
> Sure CFLAGS should be configurable, but CONFIG_TINY should always prefer
> -Os over -O2. From 'man gcc':
> 
>        -Os Optimize for size.  -Os enables all -O2 optimizations that do not
>            typically increase code size.  It also performs further optimiza-
>            tions designed to reduce code size.
> 
> If gcc regularly generates larger code with -Os the answer is to talk to
> the gcc people, not to avoid using -Os...

It's not that it does regularly, it's that it can, and if it does, it's
not really a gcc bug from what I recall.  So I don't think CONFIG_TINY
should prefer -Os over -O2 but instead we should just ask the user what
level of optimization they want.  Remember, one of the real important
parts of embedded systems is flexibility.

-- 
Tom Rini (TR1265)
http://gate.crashing.org/~trini/
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