8304928: Optimize ClassDesc.resolveConstantDesc

src/java.base/share/classes/java/lang/constant/ReferenceClassDescImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,8 +26,7 @@
 
 import java.lang.invoke.MethodHandles;
 
-import static java.lang.constant.ConstantUtils.dropFirstAndLastChar;
-import static java.lang.constant.ConstantUtils.internalToBinary;
+import static java.lang.constant.ConstantUtils.*;
 import static java.util.Objects.requireNonNull;
 
 /**
@@ -40,7 +39,7 @@ final class ReferenceClassDescImpl implements ClassDesc {
 
     /**
      * Creates a {@linkplain ClassDesc} from a descriptor string for a class or
-     * interface type
+     * interface type or an array type.
      *
      * @param descriptor a field descriptor string for a class or interface type
      * @throws IllegalArgumentException if the descriptor string is not a valid
@@ -64,19 +63,28 @@ public String descriptorString() {
     @Override
     public Class<?> resolveConstantDesc(MethodHandles.Lookup lookup)
             throws ReflectiveOperationException {
-        ClassDesc c = this;
-        int depth = ConstantUtils.arrayDepth(descriptorString());
-        for (int i=0; i<depth; i++)
-            c = c.componentType();
-
-        if (c.isPrimitive())
-            return lookup.findClass(descriptorString());
-        else {
-            Class<?> clazz = lookup.findClass(internalToBinary(dropFirstAndLastChar(c.descriptorString())));
+        if (isArray()) {
+            if (isPrimitiveArray()) {
+                return lookup.findClass(descriptor);
+            }
+            // Class.forName is slow on class or interface arrays
+            int depth = ConstantUtils.arrayDepth(descriptor);
+            Class<?> clazz = lookup.findClass(internalToBinary(descriptor.substring(depth + 1, descriptor.length() - 1)));
             for (int i = 0; i < depth; i++)
                 clazz = clazz.arrayType();
             return clazz;
         }
+        return lookup.findClass(internalToBinary(dropFirstAndLastChar(descriptor)));
+    }
+
+    /**
+     * Whether the descriptor is one of a primitive array, given this is
+     * already a valid reference type descriptor.
+     */
+    private boolean isPrimitiveArray() {
+        // All L-type descriptors must end with a semicolon; same for reference
+        // arrays, leaving primitive arrays the only ones without a final semicolon
+        return descriptor.charAt(descriptor.length() - 1) != ';';
     }
 
     /**

test/micro/org/openjdk/bench/java/lang/constant/ReferenceClassDescResolve.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package org.openjdk.bench.java.lang.constant;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+import java.lang.constant.ClassDesc;
+import java.lang.invoke.MethodHandles;
+import java.util.concurrent.TimeUnit;
+
+import static java.lang.constant.ConstantDescs.*;
+
+/**
+ * Measure the throughput of {@link ClassDesc#resolveConstantDesc} for different
+ * reference types.
+ */
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@Warmup(iterations = 3, time = 2)
+@Measurement(iterations = 6, time = 1)
+@Fork(1)
+@State(Scope.Benchmark)
+public class ReferenceClassDescResolve {
+    private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();
+    private static final ClassDesc CLASS_OR_INTERFACE = CD_String;
+    private static final ClassDesc REFERENCE_ARRAY = CD_Integer.arrayType(2);
+    private static final ClassDesc PRIMITIVE_ARRAY = CD_int.arrayType(3);
+
+    @Benchmark
+    public Class<?> resolveClassOrInterface() throws ReflectiveOperationException {
+        return (Class<?>) CLASS_OR_INTERFACE.resolveConstantDesc(LOOKUP);
+    }
+
+    @Benchmark
+    public Class<?> resolveReferenceArray() throws ReflectiveOperationException {
+        return (Class<?>) REFERENCE_ARRAY.resolveConstantDesc(LOOKUP);
+    }
+
+    @Benchmark
+    public Class<?> resolvePrimitiveArray() throws ReflectiveOperationException {
+        return (Class<?>) PRIMITIVE_ARRAY.resolveConstantDesc(LOOKUP);
+    }
+}