[Freeciv-Dev] Re: the directional system

[Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx>]

On Fri, Sep 07, 2001 at 08:33:02PM -0400, Greg Wooledge wrote:
> Raimar Falke (hawk@xxxxxxxxxxxxxxxxxxxxxxx) wrote:
> > On Fri, Sep 07, 2001 at 04:51:36AM -0700, Trent Piepho wrote:
> > > +#define DIR_REVERSE(dir) (((dir) + 4) % 8)
> > > +#define DIR_REVERSE(dir) (((dir) + 4) & 7)
> 
> > $ gcc -S -O2 a.c
> > $ cat a.s
> 
> Nice demonstration, but it only shows that your version of gcc can handle
> this optimization

This is correct.

> -- there may be other compilers out there that don't.

Than please state the compiler and the version. I don't know what
compiler are used to compile freeciv. I also don't know which compiler
supports such optimization. However I think all compilers used today
are able to perform the optimization since it is a very easy
transformation IMHO.

Please do the work and compile the small test program with various
compilers. This will give you, me and the freeciv community a better
understanding of how capable various compilers are.

> It's safer to use the bitwise AND operation.

Yes it would be safer for performance. However if performance would be
the primary goal freeciv would use X11 directly.

        Raimar

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