Rockbox mail archiveSubject: Re: Linus: bootloader main.c,1.17,1.18
Re: Linus: bootloader main.c,1.17,1.18
From: Ronald Teune <rtwolf_at_gmx.net>
Date: Tue, 12 Jul 2005 15:12:00 +0200
neat, thanks. Odd that gcc doesn't do such a simple optimisation.
Btw, if anyone else on the list doesn't know what atomic is, here's a
On Tue, 12 Jul 2005 14:51:46 +0200, <dave_at_beermex.com> wrote:
> Hi Ronald;
> or_l is not a function call - it compiles to inline code (i.e. no
> CALL/RETURN, the body is actually applied in-place)
> Furthermore, or_l is actually optimised assembler (just one assembly
> instruction!) whereas the C code "X |= Y" compiles to two assembly
> instructions, which is slower and also not atomic
>>> and_l(~0x01000000, &GPIO_OUT); -> /* GPIO24 is the Cypress chip
>>> power */
>>> GPIO_ENABLE |= 0x01000000; -> or_l(0x01000000, &GPIO_ENABLE);
>>> GPIO_FUNCTION |= 0x01000000; -> or_l(0x01000000, &GPIO_FUNCTION);
>> Not that I'm very into the rockbox code not deep c programming, but I'm
>> curious about the above code change. It seems to me that the original
>> (left) is more like standard c and probably faster (no function calls).
>> Can someone enlighten me on this one?
Received on 2005-07-12