gl_impucode???

[lam at windchime.arc.nasa.gov]

I am trying to tune my program on the VGX and the profiling statistics
returns with:

%time     seconds  cum %   cum sec  procedure (file)

 34.0     79.6100   34.0     79.61 gl_impucode (impcode.c)
  9.8     22.9100   43.8    102.52 draw_object (sg_object.c)
  4.8     11.2000   48.6    113.72 v3f (./STAPUFTIP7GT.O/gl_if.s)
  4.4     10.3400   53.0    124.06 gl_i_n3f (sgl2.s)
  4.2      9.8000   57.2    133.86 gl_i_v3f (sgl2.s)

My question is what does "gl_impucode" do?  Can someone who knows explain?

Thanks,

Tony Lam