Re: [PATCH] Replace loop by memset in sal/typesconfig/typesconfig.c

On 24/12/2012 18:29, Norbert Thiebaud wrote:
> On Mon, Dec 24, 2012 at 8:45 AM, julien2412<serval2412@yahoo.fr>  wrote:
> > Hello,
> >
> > By taking a look at the file  sal/typesconfig/typesconfig.c, GetAlignment
> > function, I wonder if we could replace the for loop by a memset to optimize
> > a bit.
> > So here's a straightforward patch:
> > diff --git a/sal/typesconfig/typesconfig.c b/sal/typesconfig/typesconfig.c
> > index 473f07a..ef52c5f 100644
> > --- a/sal/typesconfig/typesconfig.c
> > +++ b/sal/typesconfig/typesconfig.c
> > @@ -262,11 +262,9 @@ int GetAlignment( Type eT )
> >   {
> >     char  a[ 16*8 ];
> >     long  p = (long)(void*)a;
> > -  int   i;
> >
> >     /* clear a[...] to set legal value for double access */
> > -  for ( i = 0; i<  16*8; i++ )
> > -    a[i] = 0;
> > +  memset(a, 0, sizeof(a));
> >
> >     p = ( p + 0xF )&  ~0xF;
> >     for ( i = 1; i<  16; i++ )
> >
> > Would it be ok?
> well you can't remove
>   int i;
>
> since it is still used in the second for loop.
>
> and I doubt that that code is run very often... namely 4 times per
> execution of the typesconfig executable... which in turn run dozens of
> fprintf...
> I'd say that this micro-optimization would be completely
> un-measurable, and may or may not be an optimization at all depending
> on how the memset is treated.
> but sure, it is 'ok', as in it won't hurt anything.
ok let's forget it, I suppose that the one who made this loop has 
certainly good reasons for this + you must be right, micro-optimization

Julien