Message-Id: <m0zGSp7-000S4TC@inti.gov.ar>
Comments: Authenticated sender is <salvador AT natacha DOT inti DOT gov DOT ar>
From: "Salvador Eduardo Tropea (SET)" <salvador AT inti DOT gov DOT ar>
Organization: INTI
To: Tal Lavi <ranla AT post DOT tau DOT ac DOT il>, djgpp AT delorie DOT com
Date: Tue, 8 Sep 1998 15:51:47 +0000
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Subject: Re: MAJOR slowdowns in translating TP7 gfx code to DJGPP2: Suple
In-reply-to: <35F5CEA2.15AF@post.tau.ac.il>
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Tal Lavi <ranla AT post DOT tau DOT ac DOT il> wrote:

> > Why do you need `div', anyway?  Are you sure you can get away with simple
> > 32-bit division?
> 
> I need 'div' so I could calculate the quot AND rem at once, since I need
> them both.

You can use inline assembler for that.
  
> > This is dead end.  _farptr functions are already written in inline
> > assembly, and they are as fast as you can get (you *did* compile with -O2,
> > did you?), so you won't find any faster way of doing that part.  _farptr
> > is NOT your problem, look for the reasons of the slow-down elsewhere.
> 
> I tried the -O2 before, but i havn't seen any differnce (probably
> because 
> of the div slowing everything down).
> I don't usually trust a compiler to make my program faster.

I think gcc will generate faster code than you (without offense), try -O2 and 
if you won't debug use -fomit-frame-pointer too. -ffast-math (if I remmember 
well the name) helps for FPU intensive code.

> Is that thing safe, anyway?

Yes.

> Even though the main slowdown is not in the _far*, inlining the memory
> writing myself,
> will make things easier for the compiler, and will eliminate any chance
> for error.
> 
> Besides the stupid div, I could use some optimization with the FlushPage 
> routine that fills the screen to a certain color in 640x480x64K mode. 
> Any sugestions?
> 
> 	 void FlushPage(unsigned short C)
> 	 {
> 	   unsigned long i;
> 	   _farsetsel(LFBSelector[ScreenNum]);
> 	   for(i=0;i<614400;i+=2)
> 	     _farnspokew(i,C);
> 	 }

Yes, use long instead of words. Use decrement for the loop variable too.

SET 
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