wasm gc: group structurally equal different substructures into recursive group in order to benefit from using native ref.test/rest.cast instructions for classes

core/src/main/java/org/teavm/backend/wasm/generate/gc/classes/WasmGCClassGenerator.java

@@ -300,6 +300,7 @@ public class WasmGCClassGenerator implements WasmGCClassInfoProvider, WasmGCInit
                         var structName = names.topLevel(names.suggestForType(type));
                         classInfo.structure = new WasmStructure(structName,
                                 fields -> fillFields(finalClassInfo, fields, type));
+                        classInfo.structure.setNominal(true);
                         module.types.add(classInfo.structure);
                         nonInitializedStructures.add(classInfo.structure);
                     }

core/src/main/java/org/teavm/backend/wasm/generate/gc/methods/WasmGCGenerationVisitor.java

@@ -81,6 +81,7 @@ import org.teavm.backend.wasm.model.expression.WasmTest;
 import org.teavm.backend.wasm.model.expression.WasmThrow;
 import org.teavm.backend.wasm.model.expression.WasmUnreachable;
 import org.teavm.model.ClassHierarchy;
+import org.teavm.model.ElementModifier;
 import org.teavm.model.FieldReference;
 import org.teavm.model.MethodReference;
 import org.teavm.model.TextLocation;
@@ -517,7 +518,7 @@ public class WasmGCGenerationVisitor extends BaseWasmGenerationVisitor {
     }
 
     private boolean canCastNatively(ValueType type) {
-        /*if (type instanceof ValueType.Array) {
+        if (type instanceof ValueType.Array) {
             return true;
         }
         var className = ((ValueType.Object) type).getClassName();
@@ -525,8 +526,7 @@ public class WasmGCGenerationVisitor extends BaseWasmGenerationVisitor {
         if (cls == null) {
             return false;
         }
-        return !cls.hasModifier(ElementModifier.INTERFACE);*/
+        return !cls.hasModifier(ElementModifier.INTERFACE);
-        return false;
     }
 
     @Override

core/src/main/java/org/teavm/backend/wasm/model/WasmStructure.java

@@ -25,6 +25,7 @@ public class WasmStructure extends WasmCompositeType {
     private List<WasmField> fieldsStorage = new ArrayList<>();
     private WasmStructure supertype;
     private boolean indexesValid = true;
+    private boolean nominal;
 
     public WasmStructure(String name) {
         super(name);
@@ -57,6 +58,14 @@ public class WasmStructure extends WasmCompositeType {
         return false;
     }
 
+    public boolean isNominal() {
+        return nominal;
+    }
+
+    public void setNominal(boolean nominal) {
+        this.nominal = nominal;
+    }
+
     void ensureIndexes() {
         if (!indexesValid) {
             indexesValid = true;

core/src/main/java/org/teavm/backend/wasm/model/WasmTypeGraphBuilder.java

@@ -15,6 +15,9 @@
  */
 package org.teavm.backend.wasm.model;
 
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
 import org.teavm.common.Graph;
 import org.teavm.common.GraphBuilder;
 
@@ -29,9 +32,63 @@ final class WasmTypeGraphBuilder {
             visitor.currentIndex = module.types.indexOf(type);
             type.acceptVisitor(visitor);
         }
+
+        addNominalStructures(module, types, graphBuilder);
+
         return graphBuilder.build();
     }
 
+    private static void addNominalStructures(WasmModule module, Iterable<WasmCompositeType> types,
+            GraphBuilder graphBuilder) {
+        var subStructures = new HashMap<WasmStructure, List<WasmStructure>>();
+        var topLevelStructures = new ArrayList<WasmStructure>();
+        for (var type : types) {
+            if (type instanceof WasmStructure) {
+                var structure = (WasmStructure) type;
+                if (structure.isNominal()) {
+                    if (structure.getSupertype() != null) {
+                        subStructures.computeIfAbsent(structure.getSupertype(), k -> new ArrayList<>()).add(structure);
+                    } else {
+                        topLevelStructures.add(structure);
+                    }
+                }
+            }
+        }
+        mergeNominalStructures(module, topLevelStructures, 0, graphBuilder);
+        for (var entry : subStructures.entrySet()) {
+            mergeNominalStructures(module, entry.getValue(), entry.getKey().getFields().size(), graphBuilder);
+        }
+    }
+
+    private static void mergeNominalStructures(WasmModule module, List<WasmStructure> structures, int parentFieldCount,
+            GraphBuilder graphBuilder) {
+        outer: for (var i = 0; i < structures.size(); i++) {
+            for (var j = i + 1; j < structures.size(); j++) {
+                var a = structures.get(i);
+                var b = structures.get(j);
+                if (areSameStructures(parentFieldCount, a, b)) {
+                    var p = module.types.indexOf(a);
+                    var q = module.types.indexOf(b);
+                    graphBuilder.addEdge(p, q);
+                    graphBuilder.addEdge(q, p);
+                    continue outer;
+                }
+            }
+        }
+    }
+
+    private static boolean areSameStructures(int start, WasmStructure a, WasmStructure b) {
+        if (a.getFields().size() != b.getFields().size()) {
+            return false;
+        }
+        for (var i = start; i < a.getFields().size(); i++) {
+            if (a.getFields().get(i).getType() != b.getFields().get(i).getType()) {
+                return false;
+            }
+        }
+        return true;
+    }
+
     private static class GraphBuilderVisitor implements WasmCompositeTypeVisitor {
         final WasmModule module;
         final GraphBuilder graphBuilder;