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Re: [RFA] expand from SSA form (1/2)


On Sun, Apr 26, 2009 at 10:19 PM, Michael Matz <matz@suse.de> wrote:
> Hi,
>
> On Fri, 24 Apr 2009, Richard Guenther wrote:
>
>> *************** struct var_ann_d GTY(())
>> *** 234,243 ****
>> ? ?/* Used by var_map for the base index of ssa base variables. ?*/
>> ? ?unsigned base_index;
>>
>> hmm, so what is needed to remove base_index as well?
>
> Rewriting var_map_base_init() to not use var annotations. ?SSA name
> coalescing and conflict building wants to have a DECL->dense-integer
> mapping for various reasons (two-stage approach for building
> conflicts).
>
> Currently that mapping is generated by storing the next available index
> into the var annotation (to be able to read it out again when the same
> basevar is seen for a different partition). ?But this whole info is
> strictly local to the above function, so it doesn't need to live in the
> annotation. ?I could very well implement this as an array indexed by
> DECL_UID. ?The UIDs shouldn't become exceptionally large, so that seems

Hm.  DECL_UIDs are sparse (and global), it would be a bad idea to index
an array with it.  Is var_ann->common.aux already used by out-of-SSA?
(also common.rn and common.value_handle are "local" values, but they
should go as well in the end).

> feasible. ?I wouldn't want to use a hash-table for fear of slowing down
> var_map_base_init().

I think it would be not too bad ;)

Richard.


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