Re: [PATCH] Implement ipa_vr hashing.

[Aldy Hernandez <aldyh@redhat.com>]

On 5/29/23 16:51, Martin Jambor wrote:
> Hi,
> 
> On Mon, May 22 2023, Aldy Hernandez via Gcc-patches wrote:
>> Implement hashing for ipa_vr.  When all is said and done, all these
>> patches incurr a 7.64% slowdown for ipa-cp, with is entirely covered by
>> the similar 7% increase in this area last week.  So we get type agnostic
>> ranges with "infinite" range precision close to free.
> 
> Do you know why/where this slow-down happens?  Do we perhaps want to
> limit the "infiniteness" a little somehow?

It happens in ipcp_vr_lattice::meet_with_1, because we have a lot more 
sub-ranges to union.  The latest numbers are 6.6%, and as I said I've 
already improved ipa-cp by the an equal amount, so we're good :).

The infiniteness is already capped.  We start at 3 sub-ranges, and grow 
up to 255.  I suppose if this is a problem, we could write a custom 
Value_Range temporary for IPA to fit specific needs, but I'd really like 
to avoid such special casing.

> 
> Also, jump functions live for a long time, have you looked at how memory
> hungry they become?  I hope that the hashing would be good at preventing
> any issues.

See my previous mail on memory usage.

Aldy