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RE: [avr-libc-dev] Re: Add lib per devide.

From: Weddington, Eric
Subject: RE: [avr-libc-dev] Re: Add lib per devide.
Date: Tue, 23 Dec 2008 09:39:00 -0700


> -----Original Message-----
> From: 
> address@hidden 
> [mailto:address@hidden
> org] On Behalf Of David Brown
> Sent: Tuesday, December 23, 2008 9:24 AM
> To: address@hidden
> Subject: [avr-libc-dev] Re: Add lib per devide.
> Have you tried using ccache?  I haven't used it for compiling 
> avrgcc or 
> avr-libc (I haven't recompiled these myself for ages - the winavr 
> package is too good!), but I've used it for other 
> compilations on both 
> cygwin and linux.

You have to consider the type of project that avr-libc is. Avr-libc is a 
library project, with many small modules that are written in hand-optimized 
assembly, and built for many, many targets.

>From looking at the website of ccache, it seems like it is a preprocessor 
>cache. There is very little preprocessing done on these small assembly files. 
>So I really don't see that ccache would be that useful.

However, because this library is built for many targets (a lot more so, if it 
were per device), the hierarchy of dependencies is not deep but it is very 
wide, i.e. a lot of independent targets. When you have a lot of independent 
targets, they can be built in parallel using 'make -j'. This is the reason for 
the large time savings in building avr-libc.

If we built a library per device in avr-libc, I really don't worry about how 
much time it takes. However, we should then have libgcc built per device. 
Unfortunately, building gcc in parallel using 'make -j' is problematic so it 
would take a lot of time building libgcc per device.


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