Converting code from C: "omg i need more registers!&quo

when im trying to convert a code, or implement a big routine i always get confused when there is no more registers to use. Using push/pop make the code to seem so slow (hehe). What do you do to solve this issue?

THe code i'm trying to convert is:

Code:

void line_fast(int x1, int y1, int x2, int y2, byte color)
{
  int i,dx,dy,sdx,sdy,dxabs,dyabs,x,y,px,py;

  dx=x2-x1;      /* the horizontal distance of the line */
  dy=y2-y1;      /* the vertical distance of the line */
  dxabs=abs(dx);
  dyabs=abs(dy);
  sdx=sgn(dx);
  sdy=sgn(dy);
  x=dyabs>>1;
  y=dxabs>>1;
  px=x1;
  py=y1;

  VGA[(py<<8)+(py<<6)+px]=color;

  if (dxabs>=dyabs) /* the line is more horizontal than vertical */
  {
    for(i=0;i<dxabs;i++)
    {
      y+=dyabs;
      if (y>=dxabs)
      {
        y-=dxabs;
        py+=sdy;
      }
      px+=sdx;
      plot_pixel(px,py,color);
    }
  }
  else /* the line is more vertical than horizontal */
  {
    for(i=0;i<dyabs;i++)
    {
      x+=dxabs;
      if (x>=dyabs)
      {
        x-=dyabs;
        px+=sdx;
      }
      py+=sdy;
      plot_pixel(px,py,color);
    }
  }
}

ref