|
Rockbox mail archiveSubject: Re: arrays & pointersRe: arrays & pointers
From: BlueChip <cs_bluechip_at_webtribe.net>
Date: Mon, 03 Jan 2005 23:28:27 +0000 At 22:51 03/01/2005, you wrote: >Wow. What compiler are you using? afaik, the same version as the other RockBox devs ...In fact, when I created the RockBox DevKit v3 I recall including a more recent version of the sh-1 gcc (recalled due to a problem it caused when it over-optimised the grey-scale lib functions) ...I know that at least two core devs followed me in the upgrade (obviously one of those being Jens) - so I guess we are all having the same problems. And yes, I agree, the compiler SHOULD be doing that - but I have to date found several major bugs in gcc, so oversights such as optimising array access really doesn't surprise me. BC > This looks like an easy compiler optimisation to me, so I'd be amazed > that you'd need to manually do something like this (i.e. put the pointer > into a local variable and do accesses through that rather than > dereference the array more than once). I mean, seriously, this is what > compilers are *for*. > > >----- Original Message ----- From: "BlueChip" <cs_bluechip_at_webtribe.net> >To: "Rockbox development" <rockbox_at_cool.haxx.se> >Sent: Monday, January 03, 2005 8:34 PM >Subject: arrays & pointers > > >>Just saw this go in... >> >>Log Message: >>using a pointer instead of array dereferencing saves ~250 bytes >> >> From my work on the card games library ...I discovered that arrays are >> probably THE most expensive thing for our compiler. If you are going to >> reference an element in array even just twice, it is memory efficient to >> create a pointer to that element and use the pointer instead. >> >>Given the _excessive_ efficiency of it, I guess it is also faster as well! >> >>If you're going to access the pointer several times, you might even like >>to stick a "register" in front of it for extra speed :) >> >>BC >> >>_______________________________________________ >>http://cool.haxx.se/mailman/listinfo/rockbox > >_______________________________________________ >http://cool.haxx.se/mailman/listinfo/rockbox _______________________________________________ http://cool.haxx.se/mailman/listinfo/rockbox Received on 2005-01-04 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |