[Bug tree-optimization/36347] New: points-to sets should be always kept for call-clobbering

[Bug tree-optimization/36347] New: points-to sets should be always kept for call-clobbering

[rguenth at gcc dot gnu dot org]

typedef unsigned long my_uintptr_t;

int check_a(my_uintptr_t tagged_ptr);

int __attribute__((noinline)) try_a(my_uintptr_t x)
{
  my_uintptr_t heap[2];
  my_uintptr_t *hp = heap;

  hp[0] = x;
  hp[1] = 0;
  return check_a((my_uintptr_t)(void*)((char*)hp + 1));
}


<bb 2>:
  # heap_10 = VDEF <heap_9(D)>
  heap[0] = x_2(D);
  # heap_11 = VDEF <heap_10>
  heap[1] = 0;
  D.1562_4 = &heap + 1;
  D.1563_5 = (long unsigned int) D.1562_4;
  # heap_12 = VDEF <heap_11>
  D.1561_6 = check_a (D.1563_5);
  return D.1561_6;


The points-to solution for D.1562_4 is D.1562_4 = { heap }, but we drop
that to

D.1562_4, its value escapes, points-to anything

because the pointer is never dereferenced.  This causes all addressable
variables to escape at the call to check_a, which pessimizes code and
causes useless VOPs.


-- 
           Summary: points-to sets should be always kept for call-clobbering
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, alias
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36347

[Bug tree-optimization/36347] points-to sets should be always kept for call-clobbering

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2008-05-28 08:58 -------
I have a fix (fixing PR36346 fixes this as well).


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  BugsThisDependsOn|                            |36346
         AssignedTo|unassigned at gcc dot gnu   |rguenth at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2008-05-28 08:58:13
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36347

[Bug tree-optimization/36347] points-to sets should be always kept for call-clobbering

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2008-05-29 10:32 -------
Fixed.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36347

[Bug tree-optimization/36347] points-to sets should be always kept for call-clobbering

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2008-05-29 10:32 -------
Subject: Bug 36347

Author: rguenth
Date: Thu May 29 10:31:58 2008
New Revision: 136152

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=136152
Log:
2008-05-29  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/36343
        PR tree-optimization/36346
        PR tree-optimization/36347
        * tree-flow.h (clobber_what_p_points_to): Declare.
        * tree-ssa-structalias.c (set_uids_in_ptset): Whether the
        pointed-to variable is dereferenced is irrelevant to whether
        the pointer can access the pointed-to variable.
        (clobber_what_p_points_to): New function.
        * tree-ssa-alias.c (set_initial_properties): Use it.
        * tree-ssa.c (verify_flow_sensitive_alias_info): Adjust
        call clobber check for NMTs.

        * gcc.c-torture/execute/pr36343.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.c-torture/execute/pr36343.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-flow.h
    trunk/gcc/tree-ssa-alias.c
    trunk/gcc/tree-ssa-structalias.c
    trunk/gcc/tree-ssa.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36347

[Bug tree-optimization/36347] points-to sets should be always kept for call-clobbering

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2008-05-30 19:52 -------
Fixed.


-- 

rguenth at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36347