[Bug tree-optimization/25290] PHI-OPT could be rewritten so that is uses match

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25290

--- Comment #34 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #22)
> Without load/store handling, here are the following optimizations that
> either can move to match.pd already or need some extra work to do it:
> 
> * value_replacement: need to handle !single_non_singleton_phi_for_edges case
> and more than one feeder statement (2 max according to the current
> definition)

There is a secondary part to value_replacement which requires more work than
just working on the phi. I have to think of how to handle that.


> * cond_removal_in_popcount_clz_ctz_pattern: need 2 feeder statements and
> builtin call handling for feeder statements



> 
> 
> * two_value_replacement: recored as PR 100958, it can move already

Handled.

> * abs_replacement: needs PROP_gimple_lswitch so we don't change if
> statements early enough
> ** I think majority of the abs handling is already in match.pd.

This is handled.

> * minmax_replacement: has some handling of comparisions which might not be
> in the match.pd patterns already.  needs PROP_gimple_lswitch also.
> ** The handling of:
> 	 if (a <= u)
> 	   b = MAX (a, d);
> 	 x = PHI <b, u>
>    needs to moved too.
> 
> 
> For the ones which cannot move

There is a new part of minmax which I have a patch for but there is one part
missing still (recorded in PR 101024)

> * factor_out_conditional_conversion: will never move, though it needs
> improvement and moved already (PR 56223 and PR 13563)

I have an implementation which moves this over to using gimple_match_op (which
I need to a few testcases for it). Though some of this maybe should move over
to match ...

> * spaceship_replacement: cannot move to match.pd depends on use afterwards
> which is not hard to deal with in a match pattern.

I have to look at what is done for spaceship and maybe merge it in with what is
done for value_replacement (comparison after the phi) since they implement a
similar optimization.