[Bug middle-end/64928] [4.8/4.9/5 Regression] Inordinate cpu time and memory usage in "phase opt and generate" with -ftest-coverage -fprofile-arcs

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64928

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-02-09
     Ever confirmed|0                           |1

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ok, so the memory is used by out-of-SSA it seems

#5  0x0000000000c9eebc in coalesce_ssa_name ()
    at /space/rguenther/src/svn/gcc-4_9-branch/gcc/tree-ssa-coalesce.c:1330
1330      graph = build_ssa_conflict_graph (liveinfo);
(gdb) p *cl->list.htab
$10 = {entries = 0x2b19b30, size = 524287, n_elements = 77146, n_deleted = 0, 
  searches = 122189, collisions = 6508, size_prime_index = 16}

where we malloc(!) 77146 entries of size 12.

But of course bad is the conflict graph with 76063 bitmaps eating up around
1GB of memory for the first testcase (and function
___H__23__23_u8vector_2d__3e_object).

That's likely caused by the change to more aggressively coalesce anonymous
SSA names.