8198888: Reduce string allocation churn in InvokerBytecodeGenerator

Reviewed-by: psandoz, plevart

src/java.base/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java

@@ -93,6 +93,10 @@ class InvokerBytecodeGenerator {
     private ClassWriter cw;
     private MethodVisitor mv;
 
+    /** Single element internal class name lookup cache. */
+    private Class<?> lastClass;
+    private String lastInternalName;
+
     private static final MemberName.Factory MEMBERNAME_FACTORY = MemberName.getFactory();
     private static final Class<?> HOST_CLASS = LambdaForm.class;
 
@@ -602,13 +606,18 @@ class InvokerBytecodeGenerator {
         mv.visitInsn(opcode);
     }
 
-    private static String getInternalName(Class<?> c) {
+    private String getInternalName(Class<?> c) {
         if (c == Object.class)             return OBJ;
         else if (c == Object[].class)      return OBJARY;
         else if (c == Class.class)         return CLS;
         else if (c == MethodHandle.class)  return MH;
         assert(VerifyAccess.isTypeVisible(c, Object.class)) : c.getName();
-        return c.getName().replace('.', '/');
+
+        if (c == lastClass) {
+            return lastInternalName;
+        }
+        lastClass = c;
+        return lastInternalName = c.getName().replace('.', '/');
     }
 
     private static MemberName resolveFrom(String name, MethodType type, Class<?> holder) {

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

@@ -107,6 +107,11 @@ public class BytecodeDescriptor {
     }
 
     public static String unparse(Class<?> type) {
+        if (type == Object.class) {
+            return "Ljava/lang/Object;";
+        } else if (type == int.class) {
+            return "I";
+        }
         StringBuilder sb = new StringBuilder();
         unparseSig(type, sb);
         return sb.toString();
@@ -148,6 +153,8 @@ public class BytecodeDescriptor {
         char c = Wrapper.forBasicType(t).basicTypeChar();
         if (c != 'L') {
             sb.append(c);
+        } else if (t == Object.class) {
+            sb.append("Ljava/lang/Object;");
         } else {
             boolean lsemi = (!t.isArray());
             if (lsemi)  sb.append('L');