# HG changeset patch
# User twisti
# Date 1389411045 28800
# Node ID 24353c21ef34f328f991263033910f5a3dbb34ee
# Parent  805a904eae8fb49eb63cd7c197122786662b9de4
slightly better (denser) Class.isArray check

diff -r 805a904eae8f -r 24353c21ef34 graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotVMConfig.java
--- a/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotVMConfig.java	Fri Jan 10 17:47:16 2014 -0800
+++ b/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotVMConfig.java	Fri Jan 10 19:30:45 2014 -0800
@@ -1101,11 +1101,6 @@
         return (layoutHelperArrayTagTypeValue & ~layoutHelperArrayTagObjectValue) << layoutHelperArrayTagShift;
     }
 
-    /**
-     * Bit pattern in the klass layout helper that can be used to identify arrays.
-     */
-    public final int arrayKlassLayoutHelperIdentifier = 0x80000000;
-
     @HotSpotVMField(name = "ArrayKlass::_component_mirror", type = "oop", get = HotSpotVMField.Type.OFFSET) @Stable public int arrayKlassComponentMirrorOffset;
 
     @HotSpotVMField(name = "java_lang_Class::_klass_offset", type = "int", get = HotSpotVMField.Type.VALUE) @Stable public int klassOffset;
@@ -1320,7 +1315,8 @@
         }
 
         assert codeEntryAlignment > 0 : codeEntryAlignment;
-        assert (layoutHelperArrayTagObjectValue & layoutHelperArrayTagTypeValue & arrayKlassLayoutHelperIdentifier) != 0 : "object array and type array must have first bit set";
+        assert (layoutHelperArrayTagObjectValue & (1 << (Integer.SIZE - 1))) != 0 : "object array must have first bit set";
+        assert (layoutHelperArrayTagTypeValue & (1 << (Integer.SIZE - 1))) != 0 : "type array must have first bit set";
 
         return true;
     }
diff -r 805a904eae8f -r 24353c21ef34 graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/replacements/ClassSubstitutions.java
--- a/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/replacements/ClassSubstitutions.java	Fri Jan 10 17:47:16 2014 -0800
+++ b/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/replacements/ClassSubstitutions.java	Fri Jan 10 19:30:45 2014 -0800
@@ -71,7 +71,7 @@
         if (klass.equal(0)) {
             return false;
         } else {
-            return (readLayoutHelper(klass) & arrayKlassLayoutHelperIdentifier()) != 0;
+            return klassIsArray(klass);
         }
     }
 
@@ -89,7 +89,7 @@
         if (klass.notEqual(0)) {
             int accessFlags = klass.readInt(klassAccessFlagsOffset(), LocationIdentity.FINAL_LOCATION);
             if ((accessFlags & Modifier.INTERFACE) == 0) {
-                if ((readLayoutHelper(klass) & arrayKlassLayoutHelperIdentifier()) != 0) {
+                if (klassIsArray(klass)) {
                     return Object.class;
                 } else {
                     Word superKlass = klass.readWord(klassSuperKlassOffset(), LocationIdentity.FINAL_LOCATION);
@@ -109,7 +109,7 @@
     public static Class<?> getComponentType(final Class<?> thisObj) {
         Word klass = loadWordFromObject(thisObj, klassOffset());
         if (klass.notEqual(0)) {
-            if ((readLayoutHelper(klass) & arrayKlassLayoutHelperIdentifier()) != 0) {
+            if (klassIsArray(klass)) {
                 return piCast(klass.readObject(arrayKlassComponentMirrorOffset(), LocationIdentity.FINAL_LOCATION), Class.class, true, true);
             }
         }
diff -r 805a904eae8f -r 24353c21ef34 graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/replacements/HotSpotReplacementsUtil.java
--- a/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/replacements/HotSpotReplacementsUtil.java	Fri Jan 10 17:47:16 2014 -0800
+++ b/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/replacements/HotSpotReplacementsUtil.java	Fri Jan 10 19:30:45 2014 -0800
@@ -237,9 +237,22 @@
         return hub.readInt(klassLayoutHelperOffset(), LocationIdentity.FINAL_LOCATION);
     }
 
-    @Fold
-    public static int arrayKlassLayoutHelperIdentifier() {
-        return config().arrayKlassLayoutHelperIdentifier;
+    /**
+     * Checks if class {@code klass} is an array.
+     * 
+     * See: Klass::layout_helper_is_array
+     * 
+     * @param klass the class to be checked
+     * @return true if klass is an array, false otherwise
+     */
+    public static boolean klassIsArray(Word klass) {
+        /*
+         * The less-than check only works if both values are ints. We use local variables to make
+         * sure these are still ints and haven't changed.
+         */
+        final int layoutHelper = readLayoutHelper(klass);
+        final int layoutHelperNeutralValue = config().klassLayoutHelperNeutralValue;
+        return (layoutHelper < layoutHelperNeutralValue);
     }
 
     @Fold