[U-Boot] [PATCH] common: Link with GCC instead of LD
Marek Vasut
marex at denx.de
Thu Nov 1 00:45:40 CET 2012
Dear Wolfgang Denk,
> Dear Marek,
>
> In message <201210312351.35977.marex at denx.de> you wrote:
> > > Could you please explain these supposed benefits in a bit more detail?
> >
> > Yes, thanks for the review (I really needed one from you on this)!
> >
> > So, here comes the list:
> > 1) It's cool to link with gcc, duh ;-)
>
> Is it - and why exactly?
It's all the rage now (better ignore this point) ;-)
> > 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.
> > 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.
> > 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.
> > 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.
Besides, the sandbox target already uses gcc linking. Shall we also convert it
to use LD instead then ?
Best regards,
Marek Vasut
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