[U-Boot] [PATCH] common: Link with GCC instead of LD

[Wolfgang Denk]

Dear Marek,

In message <201211010045.40817.marex at denx.de> you wrote:
> 
> > > 2) You can enable LTO eventually -- long term plan -- which proved can
> > > shrink the code size a bit
> > 
> > Do you have a workign example?  You know, we don;t like adding dead
> > code...
> 
> We've been digging with Albert, but nothing we can release just yet. This is a 
> groundwork patch.

Dead code, which will not be added, then.

> > > 3) Usage of LLVM/CLANG is now much more straightforward
> > 
> > Please elucidate?
> 
> Now you can simply replace gcc with clang and that _should_ work. Sure, I expect 
> more work will be needed here, but this patch gives you all the ground to do 
> that.

I. e. it's all speculation only?  Such doesn't by much...

> > > 4) Binutils usually lag behind the GCC development a bit, by using GCC to
> > > do the link, we can remedy this problem
> > 
> > Grrrrghhhg.  I lost you here.  By not calling ld directly (where we
> > know exactly what we are doing), but through a (somewhat unknown) GCC
> > framework, we can magicly adjust any (claimed - by you) version
> > differences?   I cannot parse this.
> 
> GCC can do all the optimization magic (LTO ...) and then just let linker do the 
> linking.

You were talking about "Binutils usually lag behind the GCC
development".  Now I would like you to explain how "by using GCC to do
the link, we can remedy this problem".

You fail to provide any such explanation.

> > > But actually, the 2) is the most important part. LTO will hopefully help
> > > us optimize U-Boot for size even better than it is now. But that will
> > > still need much more research. So this is only a patch that shall
> > > prepare the groundwork for this further research.
> > 
> > As is, it's just unused or dead code that adds a lot of complexity and
> > buys nothing.  Please submit as part of a patch series that makes
> > successfull (and tested) use of LTO.
> 
> No, I won't, I don't have that part ready yet.

Then please _re_submit when you have the rest that actually needs any
such changes.

> Besides, the sandbox target already uses gcc linking. Shall we also convert it 
> to use LD instead then ?

Note that sandbox is actually very different, in such as it really
tried to implement a standard onforming C program, running in a
standard C execution environment.  This is totally different from the
bare metal code we have on any real hardware.

Best regards,

Wolfgang Denk

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