From:	Alistair Bain <AHBain AT NOSPAMPLEASEWEREBRITISH DOT pulsedesign DOT demon DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Code optimisations
Date:	Tue, 4 Nov 1997 23:27:06 +0000
Sender:	Alistair Bain <AHBain AT pulsedesign DOT demon DOT co DOT uk>
Distribution:	world
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Ok don't want to start a war here but...
I'm new-ish to C and I am looking for ways to speed up my code.
I don't care a whit about readability and maitainability of code, or
the size of code generated (As long as it runs on clean 16Mb system). I
just want the best performance poss. (for games programming).


1) structs - Are they slow? what do they compile to? 

2) unrolling loops - to what extent does -funroll-loops do this? Does -
O3 do this? Adding both I get an excecutable of exactly the same size as
using just -O. Should I just manually unroll the loops?

3) global variables - I heard, read, dreamt something about them being
faster. ie declare all variables at top of prog and just be careful
about accessing wrong ones, etc.


Any help appreciated.
Self-proclaimed gods need not reply.

Remove the (you know what) to Reply
-- 
Alistair Bain
AHBain AT NOSPAMPLEASEWEREBRITISH DOT pulsedesign DOT demon DOT co DOT uk

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