[U-Boot] [PATCH RFC 1/3] arm920t: do not set register useless

[Albert ARIBAUD]

Le 30/11/2010 09:28, Andreas Bießmann a écrit :

>>> +    beq    clear_bss        /* skip relocation */
>>> +    mov    r1, r6
>>
>> Why use r1?
>
> Use a scratch register here cause stmia Rn! does increment Rn.

> Therefore usage of r6 here would destroy the saved 'addr of
> destination'. Cause that fact we have saved the 'addr of destination' @
> beginning of relocate_code twice, once to r6 and once to r7. This is
> obviously not needed iv we change the register in copy_loop (which was
> already used in comment .. if you saw that on the end of the line).

Understood.

> I doubt if this a 'speed up' but we can have a cleaner interface. We
> have r4, r5, r6 as storage of input values to relocate_code. We do only
> use scratch registers for copy_loop, fixloop for relocation, clear_bss
> later on. We do decide if we need fixloop for relocation or if we can
> skip that and then setup the relevant scratch registers.
>
> Well this is only an RFC. I found that plus the NULL pointer stuff worth
> to mention. It is not that important to get this special patch in cause
> the current implementation do also work.

The r8 issue and the zero-filled reloc entry issue are important to pull 
in as they can cause all sorts of time-wasting issues.

> regards
>
> Andreas Bießmann

Amicalement,
-- 
Albert.