[Bug tree-optimization/63989] New: tree-ssa-strlen.c doesn't handle constant pointer plus and array refs if constant offset is smaller than known constant string length

[Bug tree-optimization/63989] New: tree-ssa-strlen.c doesn't handle constant pointer plus and array refs if constant offset is smaller than known constant string length

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989

            Bug ID: 63989
           Summary: tree-ssa-strlen.c doesn't handle constant pointer plus
                    and array refs if constant offset is smaller than
                    known constant string length
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
                CC: dimhen at gmail dot com, jakub at gcc dot gnu.org,
                    nheghathivhistha at gmail dot com, rguenth at gcc dot gnu.org,
                    trippels at gcc dot gnu.org
        Depends on: 61773
            Blocks: 63787

+++ This bug was initially created as a clone of Bug #61773 +++

char *foo (void)
{
  char *p = __builtin_malloc (64);
  char *q = __builtin_malloc (64);
  __builtin_strcat (q, "abcde");
  __builtin_strcat (p, "ab");
  p[1] = q[3];
  __builtin_strcat (p, q);
  return q;
}

gives

> ../../obj2/gcc/cc1 -quiet -O2 t.c
t.c: In function ‘foo’:
t.c:1:7: internal compiler error: in get_string_length, at
tree-ssa-strlen.c:417
 char *foo (void)
       ^
0x876c3d2 get_string_length
        /space/rguenther/tramp3d/trunk/gcc/tree-ssa-strlen.c:417
0x8772b02 get_string_length
        /space/rguenther/tramp3d/trunk/gcc/tree.h:2731
0x8772b02 handle_builtin_strlen
        /space/rguenther/tramp3d/trunk/gcc/tree-ssa-strlen.c:899

(gdb) up
#1  0x0876c3d3 in get_string_length (si=0x3c)
    at /space/rguenther/tramp3d/trunk/gcc/tree-ssa-strlen.c:417
417           gcc_assert (builtin_decl_implicit_p (BUILT_IN_STPCPY));


while trying to write a testcase that shows that handle_char_store should
handle a character copy from a known non-zero value.  Well, while really
trying to incrementally teach handle_char_store to handle arbitrary
stores.
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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 09:44:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc989

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |5.0

[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

[jakub at gcc dot gnu.org]

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.

[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

[rguenther at suse dot de]

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.

[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

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989
Bug 63989 depends on bug 61773, which changed state.

Bug 61773 Summary: [5 Regression] ICE in tree-ssa-strlen.c:417
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61773

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

[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

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 34220
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34220&action=edit
gcc5-pr63989-wip1.patch

So, for start, this untested patch deals with #c1 f1 case.  Still need to
extend handle_char_store etc.

[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

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Thu Jan  8 21:30:56 2015
New Revision: 219362

URL: https://gcc.gnu.org/viewcvs?rev=219362&root=gcc&view=rev
Log:
    PR tree-optimization/63989
    * params.def (PARAM_MAX_TRACKED_STRLENS): Increment default
    from 1000 to 10000.
    * tree-ssa-strlen.c (get_strinfo): Moved earlier.
    (get_stridx): If we don't have a record for certain SSA_NAME,
    but it is POINTER_PLUS_EXPR of some SSA_NAME we do with
    constant offset, call get_stridx_plus_constant.
    (get_stridx_plus_constant): New function.
    (zero_length_string): Don't use get_stridx here.

    * gcc.dg/strlenopt-27.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/strlenopt-27.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/params.def
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-strlen.c

[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

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.0                         |5.2

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 5.1 has been released.

[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

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.2                         |5.3

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 5.2 is being released, adjusting target milestone to 5.3.

[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

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.5                         |---
           Keywords|                            |missed-optimization