Date: Thu, 10 Sep 1998 20:48:30 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Tal Lavi <ranla AT post DOT tau DOT ac DOT il>
cc: djgpp AT delorie DOT com
Subject: Re: MAJOR slowdowns in translating TP7 gfx code to DJGPP2: Suplement 2
In-Reply-To: <ranla.15.002A2FA0@post.tau.ac.il>
Message-ID: <Pine.SUN.3.91.980910203626.10176F-100000@is>
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On Thu, 10 Sep 1998, Tal Lavi wrote:

> Can you please tell me how you can make 32-bit writes with a VLine routine?

For vertical lines, you can't.  I thought you were drawing horizontal 
lines as well.

> Can you think of any optimizations(except of writing everything in ASM)?

I don't think assembly will help you much.  If you compile with -O2, GCC 
should produce code that's quite good in this case.

But I suggest to use int's instead of shorts in this function, like this:

void VLine(unsigned x,
           int y1, int y2,
           unsigned short c)
{
  unsigned y;

  if (y1<=y2)
  {
    y1=(y1<0)?0:y1;
    y2=(y2>=480)?479:y2;
    SetScreen;
    for (y=y1;y<=y2;y++)
      PutPixelns(x,y,c);
  }
  else
  {
    y1=(y1>=640)?639:y1;
    y2=(y2<0)?0:y2;
    SetScreen;
    for (y=y2;y<=y1;y++)
      PutPixelns(x,y,c);
  }
}

This should be faster.  In general, a loop variable should always be an 
int, unless you have grave reasons to do otherwise.  int will produce the 
fastest code.

> I downloaded the bug fix for the profiler problem, but I had no idea about 
> what to do with it because of lack of documantation. I took the already built 
> libc file and was done with it.

This should be enough.  Can you now run the profiled program without 
wedging your machine?  If yes, then that problem is solved.

> I also took the libcpg.zip file. but how can I use it to profile libc 
> functions?

The easiest way is to replace your libc.a with libc_pg.a, and then relink 
your program.  (Actually, the linker should automatically link agains 
libc_pg.a when you link with -pg switch, but I don't think DJGPP is set 
that way by default, and I don't recommend that you mess with system 
files to set that up.)

Btw, I think you shouldn't be worried about profiling the library.  
Profile your code first, as most probably, the cause for the slow-down is 
in your code.