From 1d2781091c4024d306d167c3fef09075c27f6644 Mon Sep 17 00:00:00 2001
From: Geza Lore <glore@tenstorrent.com>
Date: Wed, 9 Sep 2026 20:56:24 +0100
Subject: [PATCH] Internals: Color densely in V3Graph::weaklyConnected, and
 return the count

No algorithm depends on this, so can be changed, later improvement will.
No functional change.
---
 src/V3Graph.cpp    |  5 -----
 src/V3Graph.h      |  6 ++----
 src/V3GraphAlg.cpp | 22 +++++++++++++++-------
 src/V3Reorder.cpp  |  1 -
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/src/V3Graph.cpp b/src/V3Graph.cpp
index 96772bf02..79e7898ee 100644
--- a/src/V3Graph.cpp
+++ b/src/V3Graph.cpp
@@ -198,11 +198,6 @@ void V3Graph::userClearEdges() {
     }
 }
 
-void V3Graph::clearColors() {
-    // Reset colors
-    for (V3GraphVertex& vertex : vertices()) vertex.color(0);
-}
-
 //======================================================================
 // Dumping
 
diff --git a/src/V3Graph.h b/src/V3Graph.h
index a954d43b1..a8dbe745b 100644
--- a/src/V3Graph.h
+++ b/src/V3Graph.h
@@ -364,12 +364,10 @@ public:
 
     // METHODS - ALGORITHMS
 
-    /// Clears color
-    void clearColors() VL_MT_DISABLED;
-
     /// Assign same color to all vertices in the same weakly connected component
     /// Thus different color if there's no edges between the two subgraphs
-    void weaklyConnected(V3EdgeFuncP edgeFuncp) VL_MT_DISABLED;
+    /// Colors are assigned densely, as 0 .. n-1, and 'n' is returned
+    uint32_t weaklyConnected(V3EdgeFuncP edgeFuncp) VL_MT_DISABLED;
 
     /// Assign same color to all vertices that are strongly connected
     /// Thus different color if there's no directional circuit within the subgraphs.
diff --git a/src/V3GraphAlg.cpp b/src/V3GraphAlg.cpp
index a501b96a4..ed99d0b28 100644
--- a/src/V3GraphAlg.cpp
+++ b/src/V3GraphAlg.cpp
@@ -27,6 +27,7 @@
 #include "V3Stats.h"
 
 #include <algorithm>
+#include <limits>
 #include <list>
 #include <map>
 #include <numeric>
@@ -135,21 +136,24 @@ void V3Graph::removeTransitiveEdges() { GraphAlgRemoveTransitiveEdges{this}.go()
 // Changes color()
 
 class GraphAlgWeakly final : GraphAlg<> {
+    // Sentinel color, meaning not colored yet. Colors themselves are 0 .. m_numColors-1.
+    static constexpr uint32_t UNCOLORED = std::numeric_limits<uint32_t>::max();
+
+    uint32_t m_numColors = 0;  // Number of colors assigned
+
     void main() {
         // Initialize state
-        m_graphp->clearColors();
-        // Color graph
-        uint32_t currentColor = 0;
+        for (V3GraphVertex& vertex : m_graphp->vertices()) vertex.color(UNCOLORED);
+        // Color graph, without gaps
         for (V3GraphVertex& vertex : m_graphp->vertices()) {
-            currentColor++;
-            vertexIterate(&vertex, currentColor);
+            if (vertex.color() == UNCOLORED) vertexIterate(&vertex, m_numColors++);
         }
     }
 
     void vertexIterate(V3GraphVertex* vertexp, uint32_t currentColor) {
         // Assign new color to each unvisited node
         // then visit each of its edges, giving them the same color
-        if (vertexp->color()) return;  // Already colored it
+        if (vertexp->color() != UNCOLORED) return;  // Already colored it
         vertexp->color(currentColor);
         for (V3GraphEdge& edge : vertexp->outEdges()) {
             if (followEdge(&edge)) vertexIterate(edge.top(), currentColor);
@@ -165,9 +169,13 @@ public:
         main();
     }
     ~GraphAlgWeakly() = default;
+
+    uint32_t numColors() const { return m_numColors; }
 };
 
-void V3Graph::weaklyConnected(V3EdgeFuncP edgeFuncp) { GraphAlgWeakly{this, edgeFuncp}; }
+uint32_t V3Graph::weaklyConnected(V3EdgeFuncP edgeFuncp) {
+    return GraphAlgWeakly{this, edgeFuncp}.numColors();
+}
 
 //######################################################################
 //######################################################################
diff --git a/src/V3Reorder.cpp b/src/V3Reorder.cpp
index 4129d4f62..bf233ea45 100644
--- a/src/V3Reorder.cpp
+++ b/src/V3Reorder.cpp
@@ -293,7 +293,6 @@ class ReorderVisitor final : public VNVisitor {
         for (AstNode* currp = nodep; currp; currp = currp->nextp()) {
             ReorderLogicVertex* const vtxp = currp->user3u().to<ReorderLogicVertex*>();
             const uint32_t color = vtxp->color();
-            UASSERT_OBJ(color, currp, "No node color assigned");
             if (lastOfColor[color]) new ReorderStrictEdge{m_graphp, lastOfColor[color], vtxp};
             lastOfColor[color] = vtxp;
         }