Re: [PATCH] forwprop: Fix up rotate pattern matching [PR106523]

[Aldy Hernandez <aldyh@redhat.com>]

On 1/17/23 12:09, Jakub Jelinek wrote:
> On Tue, Jan 17, 2023 at 11:59:53AM +0100, Aldy Hernandez wrote:
>>
>>
>> On 1/17/23 10:47, Jakub Jelinek wrote:
>>
>>> Aldy/Andrew, is the ranger query ok or should I use something different
>>> when check_range_stmt is non-NULL and I know on which statement to ask?
>>
>> <snip>
>>
>>> +	  int_range_max r;
>>> +	  if (!get_global_range_query ()->range_of_expr (r, rotcnt,
>>> +							 check_range_stmt))
>>> +	    return false;
>>
>> range_of_expr will work with and without a statement.  If no statement is
>> provided, it will return the global range.  So you can use the same
>> range_of_expr call with a statement or without one if you don't know it.
>>
>> Note that get_global_range_query () will always return a global query object
>> (think SSA_NAME_RANGE_INFO).  It will never use an existing ranger (for
>> example, if called within VRP or another pass that has an active ranger
>> enabled).  If simplify_rotate() may be used from some of these passes you
>> *may* want to use get_range_query() which will pick up the active ranger, or
>> a global query object if no ranger is active.
> 
> This is always in the forwprop pass.
> I think it doesn't have any active ranger instance, but I could be wrong.
> 
> A question would be if it would be worth to activate it in this spot lazily
> if it isn't active yet (and destruct at the end of the pass).

That's what it was designed for :).  If you're making sporadic requests, 
the on-demand mechanism should be fast enough.

Aldy