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Subject: [Bug tree-optimization/30567] [4.2 Regression] -O3 optimizer bug
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From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
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------- Comment #29 from rguenth at gcc dot gnu dot org  2007-04-25 16:32 -------
Oh, btw. why the may_aliases bitmap for SMT.11 is empty on entry to the loops
computing the transitive closure (it tries to, right?) is that SFT.0 is not
considered stored to in the first nested loop over pointers and addressable
vars.  Shouldn't we add the vars NMT aliases to ai->written_vars in
compute_flow_sensitive_aliasing?  This also seems to fix the problem:

Index: tree-ssa-alias.c
===================================================================
*** tree-ssa-alias.c    (revision 124151)
--- tree-ssa-alias.c    (working copy)
*************** compute_flow_sensitive_aliasing (struct 
*** 1142,1152 ****
         one).  Note that only pointers that have been dereferenced will
         have a name memory tag.  */
        if (pi->name_mem_tag && pi->pt_vars)
!       EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
!         {
!           add_may_alias (pi->name_mem_tag, referenced_var (j));
!           add_may_alias (v_ann->symbol_mem_tag, referenced_var (j));
!         }
      }
  }

--- 1142,1159 ----
         one).  Note that only pointers that have been dereferenced will
         have a name memory tag.  */
        if (pi->name_mem_tag && pi->pt_vars)
!       {
!         bool stored_to = bitmap_bit_p (ai->dereferenced_ptrs_store,
!                                        DECL_UID (SSA_NAME_VAR (ptr)));
!         EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
!           {
!             add_may_alias (pi->name_mem_tag, referenced_var (j));
!             if (stored_to)
!               bitmap_set_bit (ai->written_vars,
!                               DECL_UID (referenced_var (j)));
!             add_may_alias (v_ann->symbol_mem_tag, referenced_var (j));
!           }
!       }
      }
  }



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30567