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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/63989] tree-ssa-strlen.c doesn't handle constant pointer plus and array refs if constant offset is smaller than known constant string length
Date: Thu, 20 Nov 2014 11:20:00 -0000 [thread overview]
Message-ID: <bug-63989-4-Tr1hdC8rY2@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-63989-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989
--- Comment #2 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 20 Nov 2014, jakub at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989
>
> Jakub Jelinek <jakub at gcc dot gnu.org> changed:
>
> What |Removed |Added
> ----------------------------------------------------------------------------
> Status|UNCONFIRMED |NEW
> Last reconfirmed| |2014-11-20
> Ever confirmed|0 |1
>
> --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> So, we are talking here about e.g.
>
> int
> f1 (char *p)
> {
> __builtin_strcpy (p, "foobar");
> return __builtin_strlen (p + 2);
> }
>
> int
> f2 (char *p)
> {
> __builtin_strcpy (p, "foobar");
> p[2] = '\0';
> return __builtin_strlen (p);
> }
>
> int
> f3 (char *p)
> {
> __builtin_strcpy (p, "foobar");
> p[2] = '\0';
> return __builtin_strlen (p + 3);
> }
>
> int
> f4 (char *p)
> {
> __builtin_strcpy (p, "foobar");
> p[2] = 'z';
> return __builtin_strlen (p);
> }
>
> and then also determining using get_string_length (if constant) whether a
> character pointer dereference is known to be zero or known to be non-zero.
Well, we are mainly talking about the case where I had to XFAIL
gcc.dg/strlenopt-8.c for us now inline-expanding a two-character
memcpy to a short store.
next prev parent reply other threads:[~2014-11-20 11:20 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-20 9:31 [Bug tree-optimization/63989] New: " jakub at gcc dot gnu.org
2014-11-20 9:44 ` [Bug tree-optimization/63989] " jakub at gcc dot gnu.org
2014-11-20 11:20 ` rguenther at suse dot de [this message]
2014-11-21 9:38 ` jakub at gcc dot gnu.org
2014-12-08 17:25 ` jakub at gcc dot gnu.org
2015-01-08 21:31 ` jakub at gcc dot gnu.org
2015-04-22 12:01 ` jakub at gcc dot gnu.org
2015-07-16 9:18 ` rguenth at gcc dot gnu.org
2022-01-09 0:45 ` pinskia at gcc dot gnu.org
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