From 7539c7372dd2bee48941da75f82355c15d0a262f Mon Sep 17 00:00:00 2001
From: James Cherry <cherry@parallaxsw.com>
Date: Thu, 23 Oct 2025 08:56:22 -0700
Subject: [PATCH] Sta::vertexSlack(endpoint) speedup

Signed-off-by: James Cherry <cherry@parallaxsw.com>
---
 search/Search.cc |  3 ++-
 search/Sta.cc    | 40 +++++++++++++++++++++++-----------------
 2 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/search/Search.cc b/search/Search.cc
index 812c98d9..6cbb5a74 100644
--- a/search/Search.cc
+++ b/search/Search.cc
@@ -1074,7 +1074,8 @@ Search::findArrivals1(Level level)
   Stats stats(debug_, report_);
   int arrival_count = arrival_iter_->visitParallel(level, arrival_visitor_);
   deleteTagsPrev();
-  deleteUnusedTagGroups();
+  if (arrival_count > 0)
+    deleteUnusedTagGroups();
   stats.report("Find arrivals");
   if (arrival_iter_->empty()
       && invalid_arrivals_->empty()) {
diff --git a/search/Sta.cc b/search/Sta.cc
index 8a1d962a..8468d19e 100644
--- a/search/Sta.cc
+++ b/search/Sta.cc
@@ -3196,24 +3196,30 @@ Sta::findRequired(Vertex *vertex)
 {
   searchPreamble();
   search_->findAllArrivals();
-  search_->findRequireds(vertex->level());
-  if (variables_->crprEnabled()
-      && search_->crprPathPruningEnabled()
-      && !search_->crprApproxMissingRequireds()
-      // Clocks invariably have requireds that are pruned but it isn't
-      // worth finding arrivals and requireds all over again for
-      // the entire fanout of the clock.
-      && !search_->isClock(vertex)) {
-    // Invalidate arrivals and requireds and disable
-    // path pruning on fanout vertices with DFS.
-    int fanout = 0;
-    disableFanoutCrprPruning(vertex, fanout);
-    debugPrint(debug_, "search", 1, "resurrect pruned required %s fanout %d",
-               vertex->to_string(this).c_str(),
-               fanout);
-    // Find fanout arrivals and requireds with pruning disabled.
-    search_->findArrivals();
+  if (search_->isEndpoint(vertex)
+      // Need to include downstream required times if there is fanout.
+      && !hasFanout(vertex, search_->searchAdj(), graph_))
+    search_->seedRequired(vertex);
+  else {
     search_->findRequireds(vertex->level());
+    if (variables_->crprEnabled()
+	&& search_->crprPathPruningEnabled()
+	&& !search_->crprApproxMissingRequireds()
+	// Clocks invariably have requireds that are pruned but it isn't
+	// worth finding arrivals and requireds all over again for
+	// the entire fanout of the clock.
+	&& !search_->isClock(vertex)) {
+      // Invalidate arrivals and requireds and disable
+      // path pruning on fanout vertices with DFS.
+      int fanout = 0;
+      disableFanoutCrprPruning(vertex, fanout);
+      debugPrint(debug_, "search", 1, "resurrect pruned required %s fanout %d",
+		 vertex->to_string(this).c_str(),
+		 fanout);
+      // Find fanout arrivals and requireds with pruning disabled.
+      search_->findArrivals();
+      search_->findRequireds(vertex->level());
+    }
   }
 }