[GR-62038] Do not use field offsets to order fields.

PullRequest: graal/20115

Author: dougxc

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/Fields.java

@@ -61,6 +61,11 @@ public class Fields {
 
     private final Class<?>[] declaringClasses;
 
+    /**
+     * @see #getStableOrder()
+     */
+    private final int[] stableOrder;
+
     protected Fields(List<? extends FieldsScanner.FieldInfo> fields) {
         Collections.sort(fields);
         this.offsets = new long[fields.size()];
@@ -75,6 +80,13 @@ protected Fields(List<? extends FieldsScanner.FieldInfo> fields) {
             declaringClasses[index] = f.declaringClass;
             index++;
         }
+        this.stableOrder = new int[fields.size()];
+        List<FieldsScanner.FieldInfo> stableFields = new ArrayList<>(fields);
+        stableFields.sort(FieldsScanner.FieldInfo.STABLE_COMPARATOR);
+        for (int i = 0; i < fields.size(); i++) {
+            FieldsScanner.FieldInfo f = stableFields.get(i);
+            stableOrder[i] = fields.indexOf(f);
+        }
     }
 
     public Field getField(int i) {
@@ -274,6 +286,21 @@ public long[] getOffsets() {
         return offsets;
     }
 
+    /**
+     * Gets the indexes of the fields sorted by {@link FieldsScanner.FieldInfo#STABLE_COMPARATOR}.
+     * Here's an example of how to use this ordering:
+     *
+     * <pre>
+     * for (int idx : fields.getStableOrder()) {
+     *     String fieldName = fields.getName(idx);
+     *     // use fieldName
+     * }
+     * </pre>
+     */
+    public int[] getStableOrder() {
+        return stableOrder;
+    }
+
     /**
      * Gets the name of a field.
      *

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/FieldsScanner.java

@@ -27,6 +27,7 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
 import java.util.ArrayList;
+import java.util.Comparator;
 
 import jdk.internal.misc.Unsafe;
 
@@ -60,6 +61,21 @@ public long getOffset(Field field) {
      * Describes a field in a class during {@linkplain FieldsScanner scanning}.
      */
     public static class FieldInfo implements Comparable<FieldInfo> {
+
+        /**
+         * Sorts fields in ascending order by {@code field name + declaring class name + type name}.
+         */
+        public static final Comparator<FieldInfo> STABLE_COMPARATOR = (o1, o2) -> {
+            int res = o1.name.compareTo(o2.name);
+            if (res == 0) {
+                res = o1.declaringClass.getName().compareTo(o2.declaringClass.getName());
+                if (res == 0) {
+                    res = o1.type.getName().compareTo(o2.type.getName());
+                }
+            }
+            return res;
+        };
+
         public final long offset;
         public final String name;
         public final Class<?> type;

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/GraphDecoder.java

@@ -1456,7 +1456,7 @@ protected void readProperties(MethodScope methodScope, Node node) {
         try (DebugCloseable a = ReadPropertiesTimer.start(debug)) {
             NodeSourcePosition position = (NodeSourcePosition) readObject(methodScope);
             Fields fields = node.getNodeClass().getData();
-            for (int pos = 0; pos < fields.getCount(); pos++) {
+            for (int pos : fields.getStableOrder()) {
                 if (fields.getType(pos).isPrimitive()) {
                     long primitive = methodScope.reader.getSV();
                     fields.setRawPrimitive(node, pos, primitive);

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/GraphEncoder.java

@@ -447,7 +447,7 @@ private void add(Node node) {
 
     protected void writeProperties(Node node, Fields fields) {
         writeObjectId(node.getNodeSourcePosition());
-        for (int idx = 0; idx < fields.getCount(); idx++) {
+        for (int idx : fields.getStableOrder()) {
             if (fields.getType(idx).isPrimitive()) {
                 long primitive = fields.getRawPrimitive(node, idx);
                 writer.putSV(primitive);