> Am 03.12.2025 um 02:10 schrieb Andrew Pinski <[email protected]>:
>
> On Tue, Dec 2, 2025 at 1:37 PM Andrew MacLeod <[email protected]> wrote:
>>
>> The record() and register_relation() routines in the relation oracle
>> and folding routines currently return void. They are called when there
>> is a relation to register and there has not been a need for feedback on
>> whether one was registered or not.
>>
>> The patch which caused this PR recognized that and on-demand calculation
>> of something in the middle of the IL may not have access to relations
>> which are not yet registered. When that relation is added later
>> during the DOM walk, and then the statement encountered again, the
>> original cached version is used and any benefit of the now known
>> relation is lost.
>>
>> This was resolved by updating the timestamp of the 2 ssa-names in the
>> relation when it is registered. When a statement using those names is
>> re-examined, the use timestamp will be newer than the definition and the
>> statement will be recalculated with the relation available.
>>
>> The problem shown here is a cycle of PHIs feeding each other... and each
>> one adding a relation potentially consumed by the other. This forces the
>> other to be recalculated. This was done whether a relation was actually
>> added or not. If no new relation is added, we should not update the
>> timestamps as there is no need to recalculate.
>>
>> This patch changes the record() and register_relation() methods in the
>> both the relation oracle and fold_using_range classes . These routines
>> now return TRUE if a new relation was added, and FALSE otherwise. The
>> timestamps are only updated now if TRUE is returned.
>>
>> In order for the debugging output to make sense, its been tweaked to
>> only print that a relation is registered, not that an attempt was being
>> made.
>>
>> Bootstraps on x86_64-pc-linux-gnu with no regressions. OK?
>
> One minor suggestion. Mention in comments before register_relation's
> that false means nothing changed.
> Likewise for add_partial_equiv and equiv_oracle::record and the others.
>
> Otherwise looks good to me but I can't approve it.
I think we want to work on that. Would you be fine with being middle-end
reviewer?
Richard
> Thanks,
> Andrew
>
>>
>> Andrew
>>
