[U-Boot] lib_arm global data pointer

[Wolfgang Denk]

Dear Drasko DRASKOVIC,

In message <5ec3d7930907130900l7e043b11lcf37a0d3e161f511 at mail.gmail.com> you wrote:
> 
> > Well, that's easy - as the code has to interface with  GCC  generated
> > code, you have to stick with GCC's register usage conventions.
> >
> I think we were refering here to ATPCS (ARM-THUMB Procedure Call Standard,
> i.e. ARM ABI), which tells that first 4 args of the calee are passed by the
> caller via r0-r3, and if calee takes more args, the rest is passed via
> stack. IMHO, GCC conventions has not much to do with this. I used r10
> because there is small probability that it will be clobbered  in start.S.

When I wrote "GCC's register usage conventions" I usually mean exactly
that and not some completely different thing.

You also might want to read the README. Search for "On ARM, the
following registers are used"...

> "register volatile" makes sense only for the special case  of  global
> > or  local  register  variables. Whether or not it is implemented in a
> > specific version of GCC for a specific architecture is another story;
> > please ask this on the GCC mailing list.
> >
> OK. But since it was implemented in U-Boot and for ARM, I thought that
> anybody who wrote this will be so kind to shread some light on this (I am
> guessing that that it has something to do with ISR, but in ISR we seem to

This has nothing to do with ISRs at all. What makes you think so?

> preserve r8), and also on the membar two lines below, and spare me from
> subscribing to a huge volume gcc mailing lists for posting just one
> question. This rests for me one of the most obscure corners of U-Boot.

The GCC mailing list is where GCC experts can answer your  questions.
I'm not a GCC expert - just a happy user since version 1.35 or so...

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And please don't post HTML.

Best regards,

Wolfgang Denk

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