Re: Yet another DOM memory improvement

[Jan Hubicka <hubicka at ucw dot cz>]

> In an earlier message I indicated that moving the vrp_data information
> into the SSA_NAME itself probably wasn't that good of an idea.  I also
> suggested that a hash table might be a better means to record that
> data since typically it's going to be rather sparse.
> 
> This change turns that varray into a hash table per those ideas.  The
> memory savings is substantial on the order of many megabytes for
> Gerald's testcase -- even though we have to allocate a two word
> structure for each hash table element (I did my initial measurements
> with those structures in GGC memory, but for the final version I moved
> them into malloc'd memory).

For a record, it is roughly 3.8%, 22MB, but for some reason only at -O3
;) similar savings can be seen on insn-attrtab on all optimization
levels however.

The DOM iteration seems to be pretty expensive thing.  Did you
considered trottling it to 1 iteration by -fexpensive-optimizations so
it is disabled for -O1?

thanks,
Honza