8331114: Further improve performance of MethodTypeDesc::descriptorString

Reviewed-by: mchung, liach

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

@@ -160,7 +160,7 @@ static ClassDesc of(String packageName, String className) {
     static ClassDesc ofDescriptor(String descriptor) {
         // implicit null-check
         return (descriptor.length() == 1)
-               ? Wrapper.forPrimitiveType(descriptor.charAt(0)).primitiveClassDescriptor()
+               ? Wrapper.forPrimitiveType(descriptor.charAt(0)).classDescriptor()
                // will throw IAE on descriptor.length == 0 or if array dimensions too long
                : new ReferenceClassDescImpl(descriptor);
     }

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

@@ -226,7 +226,7 @@ static List<ClassDesc> parseMethodDescriptor(String descriptor) {
 
     private static ClassDesc resolveClassDesc(String descriptor, int start, int len) {
         if (len == 1) {
-            return Wrapper.forBasicType(descriptor.charAt(start)).primitiveClassDescriptor();
+            return Wrapper.forPrimitiveType(descriptor.charAt(start)).classDescriptor();
         }
         return ClassDesc.ofDescriptor(descriptor.substring(start, start + len));
     }

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

@@ -33,7 +33,6 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
-import java.util.StringJoiner;
 
 import static java.util.Objects.requireNonNull;
 
@@ -168,11 +167,17 @@ public String descriptorString() {
         if (desc != null)
             return desc;
 
-        var sj = new StringJoiner("", "(", ")" + returnType().descriptorString());
-        for (int i = 0; i < parameterCount(); i++) {
-            sj.add(parameterType(i).descriptorString());
+        int len = 2 + returnType.descriptorString().length();
+        for (ClassDesc argType : argTypes) {
+            len += argType.descriptorString().length();
         }
-        return cachedDescriptorString = sj.toString();
+        StringBuilder sb = new StringBuilder(len).append('(');
+        for (ClassDesc argType : argTypes) {
+            sb.append(argType.descriptorString());
+        }
+        desc = sb.append(')').append(returnType.descriptorString()).toString();
+        cachedDescriptorString = desc;
+        return desc;
     }
 
     @Override

src/java.base/share/classes/sun/invoke/util/Wrapper.java

@@ -32,7 +32,7 @@
 import java.lang.constant.ConstantDescs;
 
 public enum Wrapper {
-    //        wrapperType      simple     primitiveType  simple     char  emptyArray     format               numericClass  superClass
+    //        wrapperType      simple     primitiveType  simple     char  emptyArray     format               numericClass  superClass  classDescriptor
     BOOLEAN(  Boolean.class,   "Boolean", boolean.class, "boolean", 'Z', new boolean[0], Format.unsigned( 1), 0, 0, ConstantDescs.CD_boolean),
     // These must be in the order defined for widening primitive conversions in JLS 5.1.2
     // Avoid boxing integral types here to defer initialization of internal caches
@@ -60,9 +60,18 @@ public enum Wrapper {
     private final int      superClasses;
     private final String   wrapperSimpleName;
     private final String   primitiveSimpleName;
-    private final ClassDesc primitiveTypeDesc;
-
-    private Wrapper(Class<?> wtype, String wtypeName, Class<?> ptype, String ptypeName, char tchar, Object emptyArray, int format, int numericClass, int superClasses, ClassDesc primitiveTypeDesc) {
+    private final ClassDesc classDesc;
+
+    private Wrapper(Class<?> wtype,
+                    String wtypeName,
+                    Class<?> ptype,
+                    String ptypeName,
+                    char tchar,
+                    Object emptyArray,
+                    int format,
+                    int numericClass,
+                    int superClasses,
+                    ClassDesc classDesc) {
         this.wrapperType = wtype;
         this.primitiveType = ptype;
         this.basicTypeChar = tchar;
@@ -73,7 +82,7 @@ private Wrapper(Class<?> wtype, String wtypeName, Class<?> ptype, String ptypeNa
         this.superClasses = superClasses;
         this.wrapperSimpleName = wtypeName;
         this.primitiveSimpleName = ptypeName;
-        this.primitiveTypeDesc = primitiveTypeDesc;
+        this.classDesc = classDesc;
     }
 
     /** For debugging, give the details of this wrapper. */
@@ -380,8 +389,8 @@ public static Wrapper forBasicType(Class<?> type) {
         }
     }
 
-    /** A nominal descriptor of the primitive type */
-    public ClassDesc primitiveClassDescriptor() { return primitiveTypeDesc; }
+    /** A nominal descriptor of the wrapped type */
+    public ClassDesc classDescriptor() { return classDesc; }
 
     /** What is the primitive type wrapped by this wrapper? */
     public Class<?> primitiveType() { return primitiveType; }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2024, 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
@@ -54,11 +54,14 @@ public class MethodTypeDescFactories {
 
     private static final ClassDesc DUMMY_CD = ClassDesc.of("Dummy_invalid");
 
+    /** Dots will be replaced by the descriptor of this benchmark class. */
     @Param({
             "(Ljava/lang/Object;Ljava/lang/String;)I",
             "()V",
             "([IJLjava/lang/String;Z)Ljava/util/List;",
-            "()[Ljava/lang/String;"
+            "()[Ljava/lang/String;",
+            "(..IIJ)V",
+            "(.....................)."
     })
     public String descString;
     public MethodTypeDesc desc;
@@ -68,6 +71,7 @@ public class MethodTypeDescFactories {
 
     @Setup
     public void setup() {
+        descString = descString.replaceAll("\\.", MethodTypeDescFactories.class.descriptorString());
         desc = MethodTypeDesc.ofDescriptor(descString);
         ret = desc.returnType();
         args = desc.parameterArray();