RE: Useless statement in loop latch looks like performance regression

[Paulo Matos]

Paulo Matos


> -----Original Message-----
> From: Richard Biener [mailto:richard.guent...@gmail.com]
> Sent: 10 January 2014 13:25
> To: Paulo Matos
> Cc: gcc@gcc.gnu.org
> Subject: Re: Useless statement in loop latch looks like performance regression
> 
> Most likely changes to SSA coalescing at out-of-SSA time like
> 
> 2013-09-26  Richard Biener  <rguent...@suse.de>
> 
>         * tree-ssa-live.c (var_map_base_init): Handle SSA names with
>         DECL_IGNORED_P base VAR_DECLs like anonymous SSA names.
>         (loe_visit_block): Use gcc_checking_assert.
>         * tree-ssa-coalesce.c (create_outofssa_var_map): Use
>         gimple_assign_ssa_name_copy_p.
>         (gimple_can_coalesce_p): Adjust according to the var_map_base_init
>         change.
> 
> and an earlier patch by Jeff Law.

You're right, I tracked it down to this one:

Author: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Fri Jun 14 18:52:32 2013 +0000

        * gimple.h (gimple_can_coalesce_p): Prototype.
        * tree-ssa-coalesce.c (gimple_can_coalesce_p): New function.
        (create_outofssa_var_map, coalesce_partitions): Use it.
        * tree-ssa-uncprop.c (uncprop_into_successor_phis): Similarly.
        * tree-ssa-live.c (var_map_base_init): Use TYPE_CANONICAL
        if it's available.
    
        * gcc.dg/tree-ssa/coalesce-1.c: New test.

Thanks,

Paulo Matos

> 
> Richard.
>