From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Oleg Verych" Subject: Re: about size optimizations (Re: Not as much ccache win as I expected) Date: Sat, 14 Jun 2008 11:27:02 +0100 Message-ID: <8499950a0806140327l267186c5h621bec0ea3995842@mail.gmail.com> References: <8499950a0806131452j5dc9574dk336e9e06ee9e1785@mail.gmail.com> <1213429403.26255.298.camel@pmac.infradead.org> <8499950a0806140256o45d3696o505c02b2f34d90db@mail.gmail.com> <1213437917.26255.335.camel@pmac.infradead.org> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:cc:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=GmcKLYDTg0dQ7fTIKV1RDe055W6Iwc432gfKQ5gYK6A=; b=AKr94cIBX5Is47QH6Nb4nQWy0njc1tMzu1Jz3Y0eBjOjo8NgGPIZVHsAE7si/e9wB4 hQTuw8MQD2RzoeXCbQq/lptq5kT4J7vBEgF7SV66bowLyukEh76SMMv5a6TD4/Br9iO9 fYePv9Jng5JPhqINEyhUoyDW3PGqX0BokFczY= In-Reply-To: <1213437917.26255.335.camel@pmac.infradead.org> Content-Disposition: inline Sender: linux-kbuild-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="iso-8859-1" To: David Woodhouse Cc: linux-embedded , linux-kbuild@vger.kernel.org, segher@kernel.crashing.org > _Sometimes_ you can just append C files together and they happen to > work. But not always. A simple case where it fails would be when you > have a static variable with the same name in two different files. Afaik in the kernel global static variables are not appreciated much. I= n any case file scope can be easily added by s/// to its name in text compile stage. There are much more problems with conditional includes and other source configuration crutches. > The compiler will do the right thing there., while na=EFve concatenat= ion > of C files will not. That was an example, of course there must be pre-cc text processing sta= ge. > Of course, it's _possible_ to have external text processing cope with > this case somehow -- you'd probably feed it through the preprocessor, > then look at the output of the preprocessor and make the variable nam= es > unique, perhaps? Even before cpp. But twisted includes/ifdef's cannot be handled without= it. > And then move on to the next case which is already handled in gcc... To gain size reduction, some register-wide static variables (ints), whi= ch are usually for some state-handling, can be glued together, if whole pictur= e permits: all flags fit in limited bit range, needed shift is added text= ually. Again developer doing clear/documented semantics, text-based transformations is needed. Can it be done by GCC optimizing stages? (However Rusty may try to do that with cpp :) > But really, I'd rather just leave it to the compiler. And it's not > because I have some masochistic fascination with makefiles :) --=20 sed 'sed && sh + olecom =3D love' << '' -o--=3DO`C #oo'L O <___=3DE M -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild"= in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html