[Bug middle-end/50262] New: PTA doesn't disambiguate locally allocated heap objects from pointed to by arguments

[Bug middle-end/50262] New: PTA doesn't disambiguate locally allocated heap objects from pointed to by arguments

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50262

             Bug #: 50262
           Summary: PTA doesn't disambiguate locally allocated heap
                    objects from pointed to by arguments
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jakub@gcc.gnu.org
                CC: rguenth@gcc.gnu.org


char *r;

char
foo (char *p, int len)
{
  char *q = __builtin_malloc (len);
  *p = 1;
  *q = 2;
  r = q;
  return *p;
}

doesn't optimize return *p; into return 1; even when *q store can't alias *p.
This matters e.g. for the string length optimization I'm working on.
Testcase for the latter is e.g.:
#include <string.h>
#include <stdlib.h>

char *
foo (char *p, char *r)
{
  char *q = malloc (strlen (p) + strlen (r) + 64);
  if (q == NULL) return NULL;
  strcpy (q, p);
  strcat (q, "/");
  strcat (q, "abcde");
  strcat (q, r);
  strcat (q, "/");
  return q;
}

[Bug middle-end/50262] PTA doesn't disambiguate locally allocated heap objects from pointed to by arguments

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50262

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |alias
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2011-09-01
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-09-01 11:10:21 UTC ---
Mine.  I have some partial patches somewhere and at least an idea how to
start to disentangle the mess that causes us to give up here.

[Bug middle-end/50262] PTA doesn't disambiguate locally allocated heap objects from pointed to by arguments

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50262

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-09-29 12:35:32 UTC ---
Not disambiguated because the HEAP tag of q escapes and thus the points-to
set of q has vars_contains_global set, which then aliases with p which
just has nonlocal set.

We'd probably need a vars_contains_nonlocal and vars_contains_escaped
to distinguish the flow-sensitivity of nonlocal vs. escaped also in
the generated points-to info.

[Bug middle-end/50262] PTA doesn't disambiguate locally allocated heap objects from pointed to by arguments

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50262

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
I finally have a patch ...

[Bug middle-end/50262] PTA doesn't disambiguate locally allocated heap objects from pointed to by arguments

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50262

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Fri Nov 15 14:48:22 2013
New Revision: 204845

URL: http://gcc.gnu.org/viewcvs?rev=204845&root=gcc&view=rev
Log:
2013-11-15  Richard Biener  <rguenther@suse.de>

    PR tree-optimization/50262
    * tree-ssa-alias.h (struct pt_solution): Split
    vars_contains_global into vars_contains_nonlocal,
    vars_contains_escaped and vars_contains_escaped_heap.
    * tree-ssa-structalias.c (label_visit): Expand comment.
    (handle_lhs_call): Adjust comment.
    (set_uids_in_ptset): Set the new flags appropriately.
    (pt_solution_set): Adjust.
    (pt_solution_set_var): Likewise.
    (pt_solution_ior_into): Likewise.
    (pt_solution_includes_global): Likewise.
    (pt_solutions_intersect_1): Optimize escaped handling.
    (compute_points_to_sets): Remove heap variable globalization.
    (ipa_escaped_pt): Adjust initializer.
    (pass_data_ipa_pta): Do not run TODO_update_ssa.
    * gimple-pretty-print.c (pp_points_to_solution): Print split
    flags.
    * tree-ssa-alias.c (dump_points_to_solution): Likewise.

    * gcc.dg/tree-ssa/alias-28.c: New testcase.
    * gcc.dg/strlenopt-1.c: Adjust.
    * gcc.dg/strlenopt-1f.c: Likewise.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/alias-28.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/gimple-pretty-print.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/strlenopt-1.c
    trunk/gcc/testsuite/gcc.dg/strlenopt-1f.c
    trunk/gcc/tree-ssa-alias.c
    trunk/gcc/tree-ssa-alias.h
    trunk/gcc/tree-ssa-structalias.c

[Bug middle-end/50262] PTA doesn't disambiguate locally allocated heap objects from pointed to by arguments

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50262

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |4.9.0

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk.