[GR-69718] Fix regression due to removed Java String caching.

PullRequest: graal/22171

Author: woess

truffle/src/com.oracle.truffle.api.strings/src/com/oracle/truffle/api/strings/TStringUnsafe.java

@@ -163,7 +163,6 @@ static int getJavaStringHashMasked(String s) {
         return hash;
     }
 
-    @TruffleBoundary
     private static String allocateJavaString() {
         try {
             return (String) UNSAFE.allocateInstance(String.class);
@@ -172,10 +171,9 @@ private static String allocateJavaString() {
         }
     }
 
-    @TruffleBoundary
     static String createJavaString(byte[] bytes, int stride, int hash) {
         if (stride < (COMPACT_STRINGS_ENABLED ? 0 : 1) || stride > 1) {
-            throw new IllegalArgumentException("illegal stride!");
+            throw CompilerDirectives.shouldNotReachHere("illegal stride!");
         }
         String ret = allocateJavaString();
         UNSAFE.putInt(ret, javaStringHashFieldOffset, hash);

truffle/src/com.oracle.truffle.api.strings/src/com/oracle/truffle/api/strings/TruffleString.java

@@ -7006,13 +7006,13 @@ static String doUTF16(TruffleString a,
             if (a.isEmpty()) {
                 return "";
             }
-            TruffleString cur = a.next;
-            if (cur != null) {
+            TruffleString cur;
+            if (a.isCompatibleToIntl(Encoding.UTF_16) || (cur = a.next) == null) {
+                cur = a;
+            } else {
                 while (cur != a && !cur.isCompatibleToIntl(Encoding.UTF_16)) {
                     cur = cur.next;
                 }
-            } else {
-                cur = a;
             }
             Encoding encodingA = Encoding.get(cur.encoding());
             final AbstractTruffleString utf16String;