[Bug middle-end/33699] [4.2/4.3/4.4 regression], missing optimization on const addr area store

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

------- Comment #4 from amylaar at gcc dot gnu dot org  2009-02-08 12:49 -------
(In reply to comment #2)
> This is related to some work done in the past for auto-increment addressing
> modes

Actually, the problem with constants that are loaded into registers -
and in the same basic block, at that - is much simpler.
If the targets rtx_cost works properly, then reload_cse_move2add should
fix up this code.

We need, however, some way to deal with the case where constants are expensive
addresses; this is completely broken at the moment.  Complete unrolling of
loops accessing static arrays can create oodles of constant addresses; I've
managed to split these up with LEGITIMIZE_ADDRESS, the movsi expander, and
a patch to momory_address, however, gcse just recombines the costly constants,
irrespective of what rtx_cost and address_cost says.
And the havoc that gcse can wreak transcends basic blocks, so any attempt to
clean up after if with lesser scope is bound to be inferior.


-- 

amylaar at gcc dot gnu dot org changed:

           What    |Removed                     |Added
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                 CC|                            |amylaar at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33699