Re: GLIL->C compilation

[Stefan Israelsson Tampe <stefan.itampe@gmail.com>]

On Saturday, November 20, 2010 12:11:16 am Ludovic Courtès wrote:
> Hi,
> 
> Stefan Israelsson Tampe <stefan.itampe@gmail.com> writes:
> > #include "cfkn.h"
> > #define LOCAL_REF(i)     fp[i]
> > #define LOCAL_SET(i,v)   fp[i] = (v)
> > void cfkn3676(SCM *fp, SCM **spp)
> > {
> > 
> >  /* setup of environment */
> >  SCM *objects, *free, program, *sp, sss[100];
> >  sp = sss;
> >  program = fp[-1];
> >  objects = SCM_I_VECTOR_WELTS (SCM_PROGRAM_OBJTABLE (program));
> >  free    = SCM_PROGRAM_FREE_VARIABLES(program);
> >  /* compiled section */
> > 
> >  LCASE3666:
> > goto L3668;
> > LCASE3665:
> > sp++; *sp = LOCAL_REF(1);
> > sp++; *sp = SCM_I_MAKINUM(0);
> > sp-=2; if(!scm_is_eq(sp[1],sp[2])) goto L3669;
> > sp++; *sp = LOCAL_REF(2);
> 
> [...]
> 
> Comparing this to the VM’s bytecode interpreter should show the overhead
> incurred by instruction dispatch.
> 
> Did you try to measure this?  That’d be interesting.
> 
> Thanks,
> Ludo’.

Yes on one of my machine one loop takes about 6ns for the compiled one and 
about 50ns for the bytcode, say a factor of 7-10 for simple tasks, but 
remember
this is for rather trivial work.