From: lonniem AT mail DOT utexas DOT edu
Newsgroups: comp.os.msdos.djgpp
Subject: Inline Assembly
Date: Fri, 06 Dec 1996 21:49:10 GMT
Organization: The University of Texas at Austin, Austin, Texas
Lines: 52
Message-ID: <589tcn$8lj@geraldo.cc.utexas.edu>
NNTP-Posting-Host: slip-a-7.ots.utexas.edu
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

I'm doing some VESA stuff for maybe use in a GUI later.  I don't know
I'm basically just messing arround with it.  I've got all the VBE
functions encapsulated in a class plus some extra things of course
like BitBlt and DrawLine ().  I am in the process of converting all
the time critical portions into inline asm but when I got to the
BitBlt, the first one to be asm'ed, I could not get movl's to work at
all.  I am using movsl to copy the image 32-bits at a time per each
scanline then mov'ing the extra number of bytes into ecx then doing a
movsb to handle the extra pixels.  Heres the code

void GraphicsInterface::BltImage (int nX, int nY, int nWidth, int
nHeight, unsigned char* pSource)
{
  int pVideoMemory;
  int nNumberOfTimes;
  int nNumberOfMoves = nWidth / 4;
  int nExtraMoves = nWidth % 4;        // moving longs at a time

  pVideoMemory = nVideoMemory + __djgpp_conventional_base;
  pVideoMemory += nY * nXResolution + nX;

  for (int lcv = 0; lcv < nHeight; lcv++)
  {
    asm ("cld              \n\t"
         "rep              \n\t"
         "movsl            \n\t"
         "movl %eax, %ecx  \n\t"  // this will not work
         "rep              \n\t"
         "movsb            \n\t"
         : // no outputs
         : "a" (nExtraMoves),
           "c" (nNumberOfMoves),
           "S" (pSource),
           "D" (pVideoMemory)
         : "%eax", "%ecx", "%esi", "%edi");
    pVideoMemory += nXResolution;
    pSource += nWidth;
  }
}

GXX issues the error:
svga.cpp:199: invalid 'asm': operand number missing after %-letter
svga.cpp:199: invalid 'asm': operand number missing after %-letter

The code works if I comment out the line with the movl %eax, %ecx but
of course does not output any extra bytes over the width / 4.  I'm
using DJGPP v2.0.
Thanks for any help.

Lonnie McCullough
lonniem AT mail DOT utexas DOT edu