This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH v3] Optimize strchr to strlen
On Fri, 2016-09-23 at 23:10 +0900, Oleg Endo wrote:
> On Fri, 2016-09-23 at 14:07 +0000, Wilco Dijkstra wrote:
> >
> > After discussion (https://gcc.gnu.org/ml/gcc-patches/2016-09/msg007
> > 18
> > .html)
> > here is the latest version of the strchr patch. This uses a gimple
> > statement for
> > the pointer addition so the gsi_prev always points at the strlen
> > call.
> >
> > Optimize strchr (s, 0) to s + strlen (s). strchr (s, 0) appears a
> > common
> > idiom for finding the end of a string, however it is not a very
> > efficient
> > way of doing so. Strlen is a much simpler operation which is
> > significantly
> > faster (eg. on x86 strlen is 50% faster for strings of 8 bytes and
> > about
> > twice as fast as strchr on strings of 1KB).
> >
> > OK for commit?
> Please add PR tree-optimization/61056 to the changelog so that it
> gets linked in bugzilla.
Notice that the "PR AAA/BBB" markers from the changelog should also be
included in the SVN commit message. Otherwise the bugzilla commit hook
doesn't notice it, because it looks at the commit messages and not at
the contents of the ChangeLog files.
Cheers,
Oleg