[Bug tree-optimization/35472] New: [4.3/4.4 Regression] tree DSE is broken

[Bug tree-optimization/35472] New: [4.3/4.4 Regression] tree DSE is broken

[rguenth at gcc dot gnu dot org]

extern void abort (void);
extern void *memset (void *s, int c, __SIZE_TYPE__ n);
struct S { int i[16]; };
struct S *p;
void __attribute__((noinline))
foo(struct S *a, struct S *b) { a->i[0] = -1; p = b; }
void test (void)
{
  struct S a, b;
  memset (&a.i[0], '\0', sizeof (a.i));
  memset (&b.i[0], '\0', sizeof (b.i));
  foo (&a, &b);
  *p = a;
  *p = b;
  if (b.i[0] != -1)
    abort ();
}
int main()
{
  test();
  return 0;
}

tree DSE removes the *p = a store wrongly.  Non-executable testcase:

struct S { int i[16]; };
struct S *p;
void foo(struct S *, struct S *);
void test (void)
{
  struct S a, b;
  foo (&a, &b);
  *p = a;
  *p = b;
}


-- 
           Summary: [4.3/4.4 Regression] tree DSE is broken
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          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=35472

[Bug tree-optimization/35472] [4.3/4.4 Regression] tree DSE is broken

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         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         |2008-03-05 13:19:22
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35472

[Bug tree-optimization/35472] [4.3/4.4 Regression] tree DSE is broken

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2008-03-05 14:45 -------
We have

  # VUSE <p_7>
  p.0_1 = p;
  # a_11 = VDEF <a_8>
  # b_12 = VDEF <b_9>
  # SMT.5_13 = VDEF <SMT.5_10>
  *p.0_1 = a;
  # a_14 = VDEF <a_11>
  # b_15 = VDEF <b_12>
  # SMT.5_16 = VDEF <SMT.5_13>
  *p.0_1 = b;

This is actually a case of PR34459 and it is its testcase that actually
fails with the fix for PR27799.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  BugsThisDependsOn|                            |34459


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35472

[Bug tree-optimization/35472] [4.3/4.4 Regression] tree DSE is broken

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2008-03-05 14:56 -------
Patch in testing.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35472

[Bug tree-optimization/35472] [4.3 Regression] tree DSE is broken

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2008-03-05 16:13 -------
Fixed on the trunk, waiting for 4.3.1.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.2.3 4.4.0
           Priority|P1                          |P2
            Summary|[4.3/4.4 Regression] tree   |[4.3 Regression] tree DSE is
                   |DSE is broken               |broken
   Target Milestone|4.3.0                       |4.3.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35472

[Bug tree-optimization/35472] [4.3 Regression] tree DSE is broken

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2008-03-05 16:13 -------
Subject: Bug 35472

Author: rguenth
Date: Wed Mar  5 16:13:04 2008
New Revision: 132899

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=132899
Log:
2008-03-05  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/35472
        * tree-ssa-dse.c (dse_optimize_stmt): Do not delete a store
        whose single use_stmt has a overlapping set of loaded and
        stored symbols as that use_stmt might be a noop assignment then.

        * gcc.c-torture/execute/pr35472.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.c-torture/execute/pr35472.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-dse.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35472

[Bug tree-optimization/35472] [4.3 Regression] tree DSE is broken

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2008-03-07 09:47 -------
Subject: Bug 35472

Author: rguenth
Date: Fri Mar  7 09:47:06 2008
New Revision: 133004

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=133004
Log:
2008-03-07  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/35472
        * tree-ssa-dse.c (dse_optimize_stmt): Do not delete a store
        whose single use_stmt has a overlapping set of loaded and
        stored symbols as that use_stmt might be a noop assignment then.

        * gcc.c-torture/execute/pr35472.c: New testcase.

Added:
    branches/gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/pr35472.c
      - copied unchanged from r132899,
trunk/gcc/testsuite/gcc.c-torture/execute/pr35472.c
Modified:
    branches/gcc-4_3-branch/gcc/ChangeLog
    branches/gcc-4_3-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_3-branch/gcc/tree-ssa-dse.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35472

[Bug tree-optimization/35472] [4.3 Regression] tree DSE is broken

[rguenth at gcc dot gnu dot org]

------- Comment #6 from rguenth at gcc dot gnu dot org  2008-03-07 09:49 -------
Fixed.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
      Known to fail|                            |4.3.0
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35472