diff --git a/Changes b/Changes
index 2bd36896b..ca1ed45ed 100644
--- a/Changes
+++ b/Changes
@@ -16,7 +16,14 @@ Verilator 5.001 devel
 * This is a major new release, currently only in alpha testing.
 
 
-Verilator 4.221 devel
+Verilator 4.223 devel
+==========================
+
+**Minor:**
+
+
+
+Verilator 4.222 2022-05-02
 ==========================
 
 **Minor:**
@@ -25,14 +32,19 @@ Verilator 4.221 devel
 * Deprecate 'vluint64_t' and similar types (#3255).
 * Raise error on assignment to const in initial blocks. [Geza Lore, Shunyao CAD]
 * Issue INITIALDLY/COMBDLY/BLKSEQ warnings consistent with Verilator execution. [Geza Lore, Shunyao CAD]
+* Support LoongArch ISA multithreading (#3353) (#3354). [Xi Zhang]
 * Fix MSVC localtime_s (#3124).
 * Fix Bison 3.8.2 error (#3366). [elike-ypq]
 * Fix rare bug in -Oz (V3Localize) (#3286). [Geza Lore, Shunyao CAD]
 * Fix tracing interfaces inside interfaces (#3309). [Kevin Millis]
 * Fix filenames with dots overwriting debug .vpp files (#3373).
-* Fix including VK_USER_OBJS in make library (#3370). [Julien Margetts]
+* Fix including VK_USER_OBJS in make library (#3370) (#3382). [Julien Margetts]
+* Fix hang in generate symbol references (#3391) (#3398). [Yoda Lee]
+* Fix missing #include <memory> (#3392). [Aliaksei Chapyzhenka]
 * Fix crash in recursive module inlining (#3393). [david-sawatzke]
 * Fix --protect-ids mangling names of library methods. [Geza Lore, Shunyao CAD]
+* Fix foreach segmentation fault (#3400). [Kamil Rakoczy]
+
 
 Verilator 4.220 2022-03-12
 ==========================
diff --git a/docs/guide/contributors.rst b/docs/guide/contributors.rst
index 54e5400e2..68b17d671 100644
--- a/docs/guide/contributors.rst
+++ b/docs/guide/contributors.rst
@@ -23,14 +23,14 @@ Contributors
 Many people have provided ideas and other assistance with Verilator.
 
 Verilator is receiving major development support from the `CHIPS Alliance
-<https://chipsalliance.org>`_.
+<https://chipsalliance.org>`_ and `Shunyao CAD <https://shunyaocad.com>`_.
 
 Previous major corporate sponsors of Verilator, by providing significant
 contributions of time or funds included include: Atmel Corporation, Cavium
 Inc., Compaq Corporation, Digital Equipment Corporation, Embecosm Ltd.,
 Hicamp Systems, Intel Corporation, Mindspeed Technologies Inc., MicroTune
 Inc., picoChip Designs Ltd., Sun Microsystems Inc., Nauticus Networks Inc.,
-and SiCortex Inc.
+SiCortex Inc, and Shunyao CAD.
 
 The people who have contributed major functionality are: Byron Bradley,
 Jeremy Bennett, Lane Brooks, John Coiner, Duane Galbi, Geza Lore, Todd
diff --git a/src/V3Graph.cpp b/src/V3Graph.cpp
index d47b786a6..1b5bc1ae4 100644
--- a/src/V3Graph.cpp
+++ b/src/V3Graph.cpp
@@ -23,6 +23,8 @@
 
 #include <map>
 #include <memory>
+#include <unordered_map>
+#include <unordered_set>
 #include <vector>
 
 int V3Graph::s_debug = 0;
@@ -325,11 +327,19 @@ void V3Graph::dumpDotFile(const string& filename, bool colorAsSubgraph) const {
     *logp << "\t\t rankdir=" << dotRankDir() << "];\n";
 
     // List of all possible subgraphs
+    // Collections of explicit ranks
+    std::unordered_set<std::string> ranks;
+    std::unordered_multimap<std::string, V3GraphVertex*> rankSets;
     std::multimap<std::string, V3GraphVertex*> subgraphs;
     for (V3GraphVertex* vertexp = verticesBeginp(); vertexp; vertexp = vertexp->verticesNextp()) {
         const string vertexSubgraph
             = (colorAsSubgraph && vertexp->color()) ? cvtToStr(vertexp->color()) : "";
         subgraphs.emplace(vertexSubgraph, vertexp);
+        const string& dotRank = vertexp->dotRank();
+        if (!dotRank.empty()) {
+            ranks.emplace(dotRank);
+            rankSets.emplace(dotRank, vertexp);
+        }
     }
 
     // We use a map here, as we don't want to corrupt anything (userp) in the graph,
@@ -346,7 +356,10 @@ void V3Graph::dumpDotFile(const string& filename, bool colorAsSubgraph) const {
         if (subgr != vertexSubgraph) {
             if (subgr != "") *logp << "\t};\n";
             subgr = vertexSubgraph;
-            if (subgr != "") *logp << "\tsubgraph cluster_" << subgr << " {\n";
+            if (subgr != "") {
+                *logp << "\tsubgraph cluster_" << subgr << " {\n";
+                *logp << "\tlabel=\"" << subgr << "\"\n";
+            }
         }
         if (subgr != "") *logp << "\t";
         *logp << "\tn" << vertexp->dotName() << (n++) << "\t[fontsize=8 "
@@ -382,6 +395,24 @@ void V3Graph::dumpDotFile(const string& filename, bool colorAsSubgraph) const {
             }
         }
     }
+
+    // Print ranks
+    for (auto dotRank : ranks) {
+        *logp << "\t{ rank=";
+        if (dotRank != "sink" && dotRank != "source" && dotRank != "min" && dotRank != "max") {
+            *logp << "same";
+        } else {
+            *logp << dotRank;
+        }
+        *logp << "; ";
+        auto bounds = rankSets.equal_range(dotRank);
+        for (auto it{bounds.first}; it != bounds.second; ++it) {
+            if (it != bounds.first) *logp << ", ";
+            *logp << 'n' << numMap[it->second] << "";
+        }
+        *logp << " }\n";
+    }
+
     // Vertex::m_user end, now unused
 
     // Trailer
diff --git a/src/V3Graph.h b/src/V3Graph.h
index c8319f5a8..ae59fe4a4 100644
--- a/src/V3Graph.h
+++ b/src/V3Graph.h
@@ -218,6 +218,7 @@ public:
     virtual string dotShape() const { return ""; }
     virtual string dotStyle() const { return ""; }
     virtual string dotName() const { return ""; }
+    virtual string dotRank() const { return ""; }
     virtual uint32_t rankAdder() const { return 1; }
     virtual FileLine* fileline() const { return nullptr; }  // nullptr for unknown
     virtual int sortCmp(const V3GraphVertex* rhsp) const {