[GR-71328] Avoid VarHandle dispatch in interpreter loop for opcode fetch

PullRequest: graal/22635

Author: lewurm

substratevm/mx.substratevm/suite.py

@@ -1640,6 +1640,9 @@
                 "com.oracle.graal.pointsto",
             ],
             "requiresConcealed" : {
+                "java.base" : [
+                    "jdk.internal.misc", # Unsafe
+                ],
                 "jdk.internal.vm.ci" : [
                     "jdk.vm.ci.meta",
                     "jdk.vm.ci.meta.annotation",

substratevm/src/com.oracle.svm.interpreter.metadata/src/com/oracle/svm/interpreter/metadata/ByteUtils.java

@@ -25,15 +25,17 @@
 
 package com.oracle.svm.interpreter.metadata;
 
-import java.lang.invoke.MethodHandles;
-import java.lang.invoke.VarHandle;
+import jdk.internal.misc.Unsafe;
 
 /**
  * A collection of utility methods for dealing with bytes, particularly in byte arrays.
  */
 public final class ByteUtils {
+    private static final Unsafe UNSAFE = Unsafe.getUnsafe();
 
-    private static final VarHandle BYTE_ARRAY_VARHANDLE = MethodHandles.arrayElementVarHandle(byte[].class);
+    private static long offsetFor(int index) {
+        return Unsafe.ARRAY_BYTE_BASE_OFFSET + ((long) index * Unsafe.ARRAY_BYTE_INDEX_SCALE);
+    }
 
     /**
      * Gets a signed 1-byte value.
@@ -76,7 +78,7 @@ public static int beU1(byte[] data, int bci) {
      * @return the unsigned 1-byte value at index {@code bci} in array {@code data}
      */
     public static int volatileBeU1(byte[] data, int bci) {
-        return ((byte) BYTE_ARRAY_VARHANDLE.getVolatile(data, bci)) & 0xff;
+        return UNSAFE.getByteVolatile(data, offsetFor(bci)) & 0xff;
     }
 
     /**
@@ -87,7 +89,7 @@ public static int volatileBeU1(byte[] data, int bci) {
      * @return the unsigned 1-byte value at index {@code bci} in array {@code data}
      */
     public static int opaqueBeU1(byte[] data, int bci) {
-        return ((byte) BYTE_ARRAY_VARHANDLE.getOpaque(data, bci)) & 0xff;
+        return UNSAFE.getByteOpaque(data, offsetFor(bci)) & 0xff;
     }
 
     /**
@@ -128,7 +130,7 @@ public static int beSVar(byte[] data, int bci, boolean fourByte) {
         }
     }
 
-    public static void opaqueWrite(byte[] array, int index, byte value) {
-        BYTE_ARRAY_VARHANDLE.setOpaque(array, index, value);
+    public static void opaqueWrite(byte[] data, int bci, byte value) {
+        UNSAFE.putByteOpaque(data, offsetFor(bci), value);
     }
 }