[PartialRouter] Preserve LUT routethru arcs when unpreserving nets - #1404
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Previously, arcs leaving the INT tile were dropped when collecting the
PIPs of a preserved net, since the router projects pins to their INT
tile and would never explore them. For a net containing a LUT routethru
this broke the prev pointer chain at the CLE, so finishRouteConnection()
could not recover the existing routing once the net was unpreserved
under softPreserve.
Keep routethru PIPs in all three PIP loops so the chain stays intact.
With lutRoutethru disabled, mark the IMUX feeding such a routethru as
INACCESSIBLE: RWRoute does not normally explore non-sink PINFEED nodes,
and this one is only present because it was on a previously-preserved
net, so no other connection may claim a pin the routethru physically
occupies. Such nodes are skipped when resetting children lists, and
RouteNode.setType() gains a LOCAL_{EAST,WEST} -> INACCESSIBLE demotion.
Signed-off-by: Eddie Hung <eddie.hung@amd.com>
Signed-off-by: Eddie Hung <eddie.hung@amd.com>
clavin-xlnx
approved these changes
Aug 24, 2026
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Previously, arcs leaving the INT tile were dropped when collecting the PIPs of a preserved net, since the router projects pins to their INT tile and would never explore them. For a net containing a LUT routethru this broke the prev pointer chain at the CLE, so
finishRouteConnection()could not recover the existing routing once the net was unpreserved undersoftPreserve.Keep routethru PIPs in all three PIP loops so the chain stays intact. With
lutRoutethrudisabled, mark theIMUXfeeding such a routethru asINACCESSIBLE: RWRoute does not normally explore non-sinkPINFEEDnodes, and this one is only present because it was on a previously-preserved net, so no other connection may claim a pin the routethru physically occupies. Such nodes are skipped when resetting children lists, andRouteNode.setType()gains aLOCAL_{EAST,WEST}->INACCESSIBLEdemotion.