Subject: Re: [PATCH 2/4] Core support for --combine -fwhole-program
From: Josh Triplett <josht@us.ibm.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <1156433167.3012.119.camel@pmac.infradead.org>
References: <1156429585.3012.58.camel@pmac.infradead.org>
	 <1156433167.3012.119.camel@pmac.infradead.org>
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Date: Thu, 24 Aug 2006 10:27:18 -0700
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On Thu, 2006-08-24 at 16:26 +0100, David Woodhouse wrote:
> This patch adds a config option for COMBINE_COMPILE, adds the __global
> tag to compiler.h and makes EXPORT_SYMBOL automatically use it. It also
> contains a crappy Makefile hack which uses -fwhole-program --combine for
> all multi-obj .o files -- anything which was 
> 	obj-m := foo.o
> 	foo-objs := bar.o wibble.o 
> ... should now use gcc -o foo.o --combine -fwhole-program bar.c wibble.c
> 
> The makefile hack is known not to work properly for generated C files in
> out-of-source-tree builds, and for multi-obj files where one of the
> sources is _assembly_ instead of C. It's good enough for the proof of
> concept, until someone more clueful can do it properly though. It would
> be useful to make built-in.o build with --combine from _everything_
> which uses standard CFLAGS, rather than doing just what I've done here.

Would the generation and use of preprocessed source files ($x.c -> $x.i)
help solve the "standard CFLAGS" problem here, and allow a subsequent
single compilation of the entire kernel (sans modules) with --combine
-fwhole-program?

- Josh Triplett


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