Preserve already computed hash code in TruffleString to Java String conversion.

Author: woess

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -131,6 +131,8 @@ public abstract sealed class AbstractTruffleString permits TruffleString, Mutabl
      */
     int hashCode;
 
+    static final int MASKED_ZERO_HASH_CODE = -1;
+
     AbstractTruffleString(Object data, int offset, int length, int stride, Encoding encoding, int flags, int codePointLength, int codeRange) {
         validateData(data, offset, length, stride);
         assert isByte(stride);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -2039,7 +2039,12 @@ static String createJavaString(Node node, AbstractTruffleString a, byte[] arrayA
                                 arrayA, offsetA, a.stride(), 0,
                                 bytes, byteArrayBaseOffset(), stride, 0, a.length());
             }
-            return TStringUnsafe.createJavaString(bytes, stride);
+            int javaStringHash = a.hashCode;
+            if (javaStringHash == AbstractTruffleString.MASKED_ZERO_HASH_CODE) {
+                // hash code could be 0 or -1, treat the hash code as uninitialized
+                javaStringHash = 0;
+            }
+            return TStringUnsafe.createJavaString(bytes, stride, javaStringHash);
         }
     }
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -154,12 +154,12 @@ private static String allocateJavaString() {
     }
 
     @TruffleBoundary
-    static String createJavaString(byte[] bytes, int stride) {
+    static String createJavaString(byte[] bytes, int stride, int hash) {
         if (stride < (COMPACT_STRINGS_ENABLED ? 0 : 1) || stride > 1) {
             throw new IllegalArgumentException("illegal stride!");
         }
         String ret = allocateJavaString();
-        UNSAFE.putInt(ret, javaStringHashFieldOffset, 0);
+        UNSAFE.putInt(ret, javaStringHashFieldOffset, hash);
         UNSAFE.putByte(ret, javaStringCoderFieldOffset, (byte) stride);
         UNSAFE.putObjectVolatile(ret, javaStringValueFieldOffset, bytes);
         assert checkUnsafeStringResult(bytes, stride, ret);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -3087,6 +3087,7 @@ private static int maskZero(int rawHashCode) {
             int h = rawHashCode;
             if (h == 0) {
                 h--;
+                assert h == MASKED_ZERO_HASH_CODE;
             }
             return h;
         }