[Bug c++/14179] [3.3/3.4/3.5 Regression] out of memory

["mmitchel at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-03-08 23:08 -------
I've investigated this problem.

To some extent, this problem is inevitable.  In the old days, we used to output
assembly code for a global array element-by-element as we saw it.  That's not
what we want to do: we want to store up the array so that we can optimize loads
from fixed indices, etc.

However, we do waste a ton of memory.  We allocate a separate INTEGER_CST for
each occurrence of the same integer constant, even though there are only a few
of them.  We allocate an entirely new list of constants when we refactor the
brace-enclosed form (essentially adding braces that C++ says you can omit).  We
allocate an integer constant for every possible index into the array, which has
8 million entries.

We should be representing the initializer with a structure like this:

  struct init_group { 
    struct init_group *next;
    tree designator; /* The designator for the first element in the array.  */
    tree elts[];
  };

rather than a linked-list per element.  That would be far more efficient for
large arrays and a win even for small arrays.

None of this is going to get fixed until 3.5, however.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.0                       |3.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14179