Re: [2.6 patch] re-add -ffreestanding

[Adrian Bunk <bunk@stusta.de>]

On Wed, Aug 30, 2006 at 07:39:05PM +0100, Russell King wrote:
> On Wed, Aug 30, 2006 at 08:13:58PM +0200, Andi Kleen wrote:
> > On Wednesday 30 August 2006 19:57, Adrian Bunk wrote:
> > > I got the following compile error with gcc 4.1.1 when trying to compile 
> > > kernel 2.6.18-rc4-mm2 for m68k:
> > 
> > If anything then -ffreestanding needs to be added to arch/m68k/Makefile
> > (assuming it doesn't compile at all right now)
> 
> Looking at the effect of -ffreestanding on ARM, it appears that on one
> hand, the overall image size is reduced by 0.016% but we end up with worse
> code - eg, strlen() of the same string in the same function evaluated
> multiple times vs once without -ffreestanding.
> 
> The difference probably comes down to the lack of __attribute__((pure))
> on our string functions in linux/string.h.
> 
> If we are going to go for -ffreestanding, we need to fix linux/string.h
> in that respect _first_.

We are talking about reverting the patch that removed -ffreestanding, 
and that broke at least two architectures although it wrongly claimed 
it would have been a safe patch.

I agree that there is room for improvement at our string functions, but 
small optimizations like the ones you are mentioning are not much 
when talking about reverting a patch that is both theoretically wrong 
and has proven practically to cause problems.

> Russell King

cu
Adrian

-- 

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