8339290: Optimize ClassFile Utf8EntryImpl#writeTo

src/java.base/share/classes/java/lang/StringCoding.java

@@ -34,13 +34,19 @@ class StringCoding {
 
     private StringCoding() { }
 
-    public static boolean hasNegativeOrZeros(byte[] ba) {
-        for (int i = 0, len = ba.length; i < len; i++) {
+    public static boolean isLatin1GreaterThanZero(String s) {
+        byte[] value;
+        return s.coder() == String.LATIN1 && countGreaterThanZero(value = s.value(), 0, value.length) == value.length;
+    }
+
+    public static int countGreaterThanZero(byte[] ba, int off, int len) {
+        int limit = off + len;
+        for (int i = off; i < limit; i++) {
             if (ba[i] <= 0) {
-                return true;
+                return i - off;
             }
         }
-        return false;
+        return len;
     }
 
     public static boolean hasNegatives(byte[] ba, int off, int len) {

src/java.base/share/classes/java/lang/System.java

@@ -2594,8 +2594,8 @@ public void inflateBytesToChars(byte[] src, int srcOff, char[] dst, int dstOff,
                 StringLatin1.inflate(src, srcOff, dst, dstOff, len);
             }
 
-            public boolean hasNegativeOrZeros(String s) {
-                return s.coder() == String.UTF16 || StringCoding.hasNegativeOrZeros(s.value());
+            public boolean isLatin1GreaterThanZero(String s) {
+                return StringCoding.isLatin1GreaterThanZero(s);
             }
 
             public int decodeASCII(byte[] src, int srcOff, char[] dst, int dstOff, int len) {

src/java.base/share/classes/jdk/internal/access/JavaLangAccess.java

@@ -392,10 +392,9 @@ public interface JavaLangAccess {
     void inflateBytesToChars(byte[] src, int srcOff, char[] dst, int dstOff, int len);
 
     /**
-     * Calculates whether the string value is 0 or a negative number when the coder is LATIN1.
-     * If the coder is UTF16, it always returns true.
+     * Determine if the coder is Latin1 and the elements of the value array are greater than 0
      */
-    boolean hasNegativeOrZeros(String s);
+    boolean isLatin1GreaterThanZero(String s);
 
     /**
      * Decodes ASCII from the source byte array into the destination

src/java.base/share/classes/jdk/internal/classfile/impl/AbstractPoolEntry.java

@@ -421,7 +421,7 @@ void writeTo(BufWriterImpl pool) {
                 }
                 pool.writeU1(tag);
                 pool.writeU2(charLen);
-                if (!JLA.hasNegativeOrZeros(stringValue)) {
+                if (JLA.isLatin1GreaterThanZero(stringValue)) {
                     pool.writeBytesDirect(stringValue);
                 } else {
                     writeToSlow(pool);