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Rockbox mail archiveSubject: Re: Linus: bootloader main.c,1.17,1.18Re: Linus: bootloader main.c,1.17,1.18
From: Ronald Teune <rtwolf_at_gmx.net>
Date: Tue, 12 Jul 2005 15:12:00 +0200 Hi Dave, 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 clear description: http://www-128.ibm.com/developerworks/library/pa-atom/ Ronald 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 > > Regards, > d > >> Hi, >> >>> 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 >> code >> (left) is more like standard c and probably faster (no function calls). >> Can someone enlighten me on this one? >> >> Ronald _______________________________________________ http://cool.haxx.se/mailman/listinfo/rockbox Received on 2005-07-12 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |