On 8/16/22 06:25, Aldy Hernandez wrote:
On Mon, Aug 15, 2022 at 11:53 AM Richard Biener <rguent...@suse.de> wrote:
The remaining issue I have with the path_range_query is that
we re-use the same instance in the back threader but the
class doesn't provide any way to "restart", aka give m_path
a lifetime. The "start a new path" API seems to essentially
be compute_ranges (), but there's no convenient way to end.
It might be more appropriate to re-instantiate the path_range_query,
though that comes at a cost. Or abstract an actual query, like
adding a
Yes, compute_ranges() is the way to start a new path. It resets exit
dependencies, the path, relations, etc. I think it would be clearer
to name it set_path (or reset_path if we want to share nomenclature
with the path_oracle).
Instantiating a new path_range_query per path is fine, as long as you
allocate the ranger it uses yourself, instead of letting
path_range_query allocate it. Instantiating a new ranger does have a
cost, and it's best to let path_range_query re-use a ranger from path
to path. This is why path_range_query is (class) global in the
backwards threader. Andrew mentioned last year making the ranger
start-up 0-cost, but it still leaves the internal caching the ranger
will do from path to path (well, the stuff outside the current path,
cause the stuff inside the path is irrelevant since it'll get
recalculated).
Yes, you will want to have one instance of ranger regardless... just
pass it to whatever/however many other instances you want to build paths
from.
Ranger itself is primarily to provide range-on-entry to the path.
Trying to use it for values within the path would bring in values
outside the path as it doesnt understand you have selected on certain
edges along the way.
The GORI engine within ranger can be utilized within the path because
GORI never looks outside the basic block being asked about, other than
thru the range-query that is provided to it. SO its perfectly safe to
use within the path.
As both GORI and ranger cache things and share the def chains, its far
more efficient to have a global instance that is just utilized. Even a
zero-cost start up would incur costs as it recalculates the same things
over and over
Andrew
