On Thu, Jun 04, 2015 at 02:33:19PM +0200, Jakub Jelinek wrote:
> On Thu, Jun 04, 2015 at 12:26:03PM +0000, Joseph Myers wrote:
> > > Again is this worth a gcc pass?
> >
> > This isn't a matter of compiler passes; it's additional checks in existing
> > built-in function handling. Maybe that built-in function handling should
> > move to the match-and-simplify infrastructure (some, for libm functions
> > and bswap, already has) to make this even simpler to implement.
>
> GCC already has a pass that attempts to track known and earlier computed
> lengths of strings, and do various transformations and optimizations based
> on that, see the tree-ssa-strlen.c pass. Most of that you really can't do
> at the glibc headers level.
>
Yes, I was writing down ideas that I have and this was one of these. I
didn't knew it does transformations, just checked that it doesn't use
length from stpcpy or in
int foo(char *s)
{
int l = strlen (s);
char *p = strchr (s,'a');
return p+l;
}
