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[patch] PR21639 fix





The "scalar_evolution_info" hash-table gets corrupted during pass
'lower_vector_ssa'. What happens is that during vectorization analysis new
entries in the hash-table are created, but the call to ggc_collect in the
subsequent pass 'lower_vector_ssa' frees up this data. Later on
complete-loop-unroll ICEs when using the data in the hash-table. This
happens because:

>there are several places in loop opts that are not GGC-safe (in
>particular the tree nodes refered from loop structures are not
>seen by garbage collector, and I think there are some other instances).
>
>So at the moment, you cannot run ggc_collect inside loop opts.

(as pointed out by Zdenek in
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21639).

The simplest thing to do until loop optimizations are made GGC-safe is to
remove the call to ggc_collect from pass_lower_vector.

This patch also fixes an ICE (segmentation fault) in SPEC's gap and mesa.

Bootstrapped and tested on powerpc-apple-darwin.

ok to install?

thanks,
dorit

Changelog:

      * tree-complex.c (pass_lower_vector_s): Remove TODO_ggc_collect.

Patch:

Index: tree-complex.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-complex.c,v
retrieving revision 2.24
diff -c -3 -p -r2.24 tree-complex.c
*** tree-complex.c      27 Apr 2005 16:50:14 -0000      2.24
--- tree-complex.c      25 May 2005 15:48:18 -0000
*************** struct tree_opt_pass pass_lower_vector_s
*** 1051,1057 ****
    0,                                  /* properties_destroyed */
    0,                                  /* todo_flags_start */
    TODO_dump_func | TODO_update_ssa    /* todo_flags_finish */
!     | TODO_ggc_collect | TODO_verify_ssa
      | TODO_verify_stmts | TODO_verify_flow,
    0                                   /* letter */
  };
--- 1051,1057 ----
    0,                                  /* properties_destroyed */
    0,                                  /* todo_flags_start */
    TODO_dump_func | TODO_update_ssa    /* todo_flags_finish */
!     | TODO_verify_ssa
      | TODO_verify_stmts | TODO_verify_flow,
    0                                   /* letter */
  };


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