[Bug lto/51497] [4.7 Regression] The run time for the polyhedron test nf.f90 is ~10% slower with -flto after revision 182107

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51497

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-12-14 12:50:52 UTC ---
Created attachment 26080
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26080
patch candidate

Ok, so the reason is that we now stream the VLA types for, for example 'x',
locally.  Thus they do not go through the type merging machinery (no
problem) - but they also do not get a TYPE_CANONICAL computed, which would
not be bad either would it be itself, but it is NULL_TREE and thus
references to such VLA arrays get alias-set zero.

The function local LTO sections are not structured in a way we can
arrange to call uniquify_nodes, but we should be able to fixup
canonical types (and variant types).