[Bug tree-optimization/51506] Function cloning misses constant struct

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51506

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011-12-12
                 CC|                            |jamborm at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org
     Ever Confirmed|0                           |1
           Severity|normal                      |enhancement

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-12-12 10:02:22 UTC ---
We currently do not easily see that they are constant:

  D.1599.a = 6;
  D.1599.b = 1;
  D.1603_1 = compute_dint (D.1599, 1);

but we could in theory improve our IL by not forcing the aggregate argument
to a temporary during gimplification of

  rv = compute_dint (<<< Unknown tree: compound_literal_expr
    struct dint D.1599 = {.a=6, .b=1}; >>>, 1) + rv;

but simply allow !is_gimple_reg_type CONSTRUCTORs that are TREE_CONSTANT,
thus have

  D.1603_1 = compute_dint ({.a=6, .b=1}, 1);

in the IL.  That would still require ipa-cp to handle aggregates though.

The above would also mean that

  D.1599 = {.a=6, .b=1};

would be valid GIMPLE (I see no good reason to disallow this either).