[GR-53821] Use a non-cryptographic hash for IsolatedSpeculationReasonEncoding.

PullRequest: graal/17671

Author: Christian Wimmer

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/util/Digest.java

@@ -50,7 +50,7 @@ public final class Digest {
     private record LongLong(long l1, long l2) {
     }
 
-    private static final char[] DIGITS = {
+    private static final byte[] DIGITS = {
                     '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                     'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
                     'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
@@ -92,20 +92,29 @@ public static String digest(byte[] bytes) {
      * Hashes the passed range of the byte array parameter and returns the encoding of the hash.
      */
     public static String digest(byte[] bytes, int offset, int length) {
-        LongLong hash = MurmurHash3_x64_128(bytes, offset, length, HASH_SEED);
-
-        StringBuilder result = new StringBuilder(DIGEST_SIZE);
-        encodeBase62(hash.l1, result);
-        encodeBase62(hash.l2, result);
+        String result = new String(digestAsByteArray(bytes, offset, length), StandardCharsets.UTF_8);
         assert result.length() == DIGEST_SIZE : "--" + result + "--";
         return result.toString();
     }
 
-    private static void encodeBase62(long value, StringBuilder result) {
+    /**
+     * Hashes the passed range of the byte array parameter and returns the encoding of the hash as a
+     * new byte array.
+     */
+    public static byte[] digestAsByteArray(byte[] bytes, int offset, int length) {
+        LongLong hash = MurmurHash3_x64_128(bytes, offset, length, HASH_SEED);
+
+        byte[] array = new byte[DIGEST_SIZE];
+        encodeBase62(hash.l1, array, 0);
+        encodeBase62(hash.l2, array, BASE62_DIGITS_PER_LONG);
+        return array;
+    }
+
+    private static void encodeBase62(long value, byte[] result, int resultIndex) {
         long cur = value;
         int base = DIGITS.length;
         for (int i = 0; i < BASE62_DIGITS_PER_LONG; i++) {
-            result.append(DIGITS[NumUtil.safeToInt(Long.remainderUnsigned(cur, base))]);
+            result[resultIndex + i] = DIGITS[NumUtil.safeToInt(Long.remainderUnsigned(cur, base))];
             cur = Long.divideUnsigned(cur, base);
         }
         GraalError.guarantee(cur == 0, "Too few loop iterations processing digits");

substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/isolated/IsolatedSpeculationReasonEncoding.java

@@ -27,13 +27,11 @@
 import java.io.ByteArrayOutputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
-import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
 
 import com.oracle.svm.core.graal.meta.SharedRuntimeMethod;
 
-import jdk.vm.ci.common.JVMCIError;
+import jdk.graal.compiler.util.Digest;
 import jdk.vm.ci.meta.ResolvedJavaMethod;
 import jdk.vm.ci.meta.ResolvedJavaType;
 
@@ -43,10 +41,6 @@ final class IsolatedSpeculationReasonEncoding extends ByteArrayOutputStream impl
     private DataOutputStream dos = new DataOutputStream(this);
     private byte[] result;
 
-    IsolatedSpeculationReasonEncoding() {
-        super(SHA1_LENGTH);
-    }
-
     private void checkOpen() {
         if (result != null) {
             throw new IllegalArgumentException("Cannot update closed speculation encoding");
@@ -92,8 +86,8 @@ public void addType(ResolvedJavaType type) {
     }
 
     private void addImageHeapObject(Object object, int nullValue) {
+        checkOpen();
         if (!addNull(object, nullValue)) {
-            checkOpen();
             try {
                 dos.writeLong(ImageHeapObjects.ref(object).rawValue());
             } catch (IOException e) {
@@ -104,8 +98,8 @@ private void addImageHeapObject(Object object, int nullValue) {
 
     @Override
     public void addString(String value) {
+        checkOpen();
         if (!addNull(value, NULL_STRING)) {
-            checkOpen();
             try {
                 dos.writeChars(value);
             } catch (IOException e) {
@@ -142,43 +136,15 @@ private boolean addNull(Object o, int nullValue) {
         return false;
     }
 
-    /**
-     * Prototype SHA1 digest that is cloned before use.
-     */
-    private static final MessageDigest SHA1 = getSHA1();
-    private static final int SHA1_LENGTH = SHA1.getDigestLength();
-
-    private static MessageDigest getSHA1() {
-        try {
-            MessageDigest sha1 = MessageDigest.getInstance("SHA-1");
-            sha1.clone();
-            return sha1;
-        } catch (CloneNotSupportedException | NoSuchAlgorithmException e) {
-            // Should never happen given that SHA-1 is mandated in a
-            // compliant Java platform implementation.
-            throw new JVMCIError("Expect a cloneable implementation of a SHA-1 message digest to be available", e);
-        }
-    }
-
     /**
      * Gets the final encoded byte array and closes this encoding such that any further attempts to
      * update it result in an {@link IllegalArgumentException}.
      */
     byte[] getByteArray() {
         if (result == null) {
-            if (count > SHA1_LENGTH) {
-                try {
-                    MessageDigest md = (MessageDigest) SHA1.clone();
-                    md.update(buf, 0, count);
-                    result = md.digest();
-                } catch (CloneNotSupportedException e) {
-                    throw new InternalError(e);
-                }
+            if (count > Digest.DIGEST_SIZE) {
+                result = Digest.digestAsByteArray(buf, 0, count);
             } else {
-                if (buf.length == count) {
-                    // No need to copy the byte array
-                    return buf;
-                }
                 result = Arrays.copyOf(buf, count);
             }
             dos = null;