On Sat, Feb 15, 2014 at 10:50:02AM +0100, Richard Biener wrote:
> On Sat, Feb 15, 2014 at 10:45 AM, Prathamesh Kulkarni
> <bilbotheelffri...@gmail.com> wrote:
> > On Sat, Feb 15, 2014 at 2:28 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> >> On Sat, Feb 15, 2014 at 02:23:24PM +0530, Prathamesh Kulkarni wrote:
> >>> This patch folds strchr (e, 0) to e + strlen (e), if e has no
> >>> side-effects.
> >>> Bootstrapped, regtested on x86_64-unknown-linux-gnu
> >>> Ok for trunk ?
> >>
> >> Why do you think it is a good idea? It is often very much the opposite.
> > I maybe completely wrong, but since strchr(p, 0), matches each
> > character of p with c until '\0' is found, I thought it would be
> > faster to call strlen, since strlen would just skip over characters upto
> > '\0'.
> > Also, I saw this committed in llvm trunk recently, and thought it
> > might be a good idea:
> > http://llvm-reviews.chandlerc.com/rL200736
>
> If it ends up being a good idea then please add this transform to
> tree-ssa-strlen.c,
> not to GENERIC builtins folding.
>
No, if that transform is good idea it should be added to headers. Also
this will not match anything as with O1 and higher it already is
transformed to rawmemchr(x, 0) as in program below.
#include <string.h>
char *
foo (char *x)
{
return strchr (x, 0);
}
