[Bug tree-optimization/45970] New: tree DSE misses many obvious dead stores

[Bug tree-optimization/45970] New: tree DSE misses many obvious dead stores

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45970

           Summary: tree DSE misses many obvious dead stores
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jakub@gcc.gnu.org


struct A { char c[4]; } a, b;

void
f1 (void)
{
  __builtin_memcpy (&a.c[0], "a", 1);
  a = b;
}

void
f2 (void)
{
  __builtin_memcpy (&a.c[0], "a", 1);
  __builtin_memcpy (&a.c[0], "cdef", 4);
}

isn't optimized by tree DSE.  RTL DSE can handle it, but only on some targets
(there are issues with calls to builtins if they were expanded as calls and
args aren't in registers etc.).

[Bug tree-optimization/45970] tree DSE misses many obvious dead stores

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45970

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2010.10.11 14:48:15
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1
           Severity|normal                      |enhancement

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-10-11 14:48:15 UTC ---
Confirmed, mine.

[Bug tree-optimization/45970] tree DSE misses many obvious dead stores

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45970

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.6.0

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-10-13 13:03:58 UTC ---
Fixed on trunk.

[Bug tree-optimization/45970] tree DSE misses many obvious dead stores

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45970

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-10-13 13:03:37 UTC ---
Author: rguenth
Date: Wed Oct 13 13:03:31 2010
New Revision: 165422

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=165422
Log:
2010-10-13  Richard Guenther  <rguenther@suse.de>

    PR tree-optimization/45970
    * tree-ssa-alias.h (stmt_kills_ref_p): Declare.
    * tree-ssa-alias.c (stmt_kills_ref_p_1): New function.
    (stmt_kills_ref_p): Likewise.
    * tree-ssa-dse.c (dse_optimize_stmt): Use it.

    * gcc.dg/tree-ssa/ssa-dse-13.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-13.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-alias.c
    trunk/gcc/tree-ssa-alias.h
    trunk/gcc/tree-ssa-dse.c