src/jdk/nashorn/internal/runtime/linker/NashornGuards.java

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rev 755 : 8035948: Redesign property listeners for shared classes
Reviewed-by: sundar, lagergren
rev 758 : 8021350: Share script classes between threads/globals within context
Reviewed-by: lagergren, sundar

*** 27,36 **** --- 27,41 ---- import static jdk.nashorn.internal.lookup.Lookup.MH; import java.lang.invoke.MethodHandle; import java.lang.invoke.MethodHandles; + import java.lang.ref.WeakReference; + import jdk.internal.dynalink.CallSiteDescriptor; + import jdk.nashorn.internal.codegen.ObjectClassGenerator; + import jdk.nashorn.internal.objects.Global; + import jdk.nashorn.internal.runtime.Property; import jdk.nashorn.internal.runtime.PropertyMap; import jdk.nashorn.internal.runtime.ScriptFunction; import jdk.nashorn.internal.runtime.ScriptObject; /**
*** 38,47 **** --- 43,53 ---- */ public final class NashornGuards { private static final MethodHandle IS_SCRIPTOBJECT = findOwnMH("isScriptObject", boolean.class, Object.class); private static final MethodHandle IS_SCRIPTFUNCTION = findOwnMH("isScriptFunction", boolean.class, Object.class); private static final MethodHandle IS_MAP = findOwnMH("isMap", boolean.class, Object.class, PropertyMap.class); + private static final MethodHandle SAME_OBJECT = findOwnMH("sameObject", boolean.class, Object.class, WeakReference.class); private static final MethodHandle IS_INSTANCEOF_2 = findOwnMH("isInstanceOf2", boolean.class, Object.class, Class.class, Class.class); // don't create me! private NashornGuards() { }
*** 73,92 **** --- 79,158 ---- public static MethodHandle getMapGuard(final PropertyMap map) { return MH.insertArguments(IS_MAP, 1, map); } /** + * Determine whether the given callsite needs a guard. + * @param property the property, or null + * @param desc the callsite descriptor + * @return true if a guard should be used for this callsite + */ + static boolean needsGuard(final Property property, final CallSiteDescriptor desc) { + return property == null || property.isConfigurable() + || property.isBound() || !ObjectClassGenerator.OBJECT_FIELDS_ONLY + || !NashornCallSiteDescriptor.isFastScope(desc) || property.canChangeType(); + } + + /** + * Get the guard for a property access. This returns an identity guard for non-configurable global properties + * and a map guard for everything else. + * + * @param sobj the first object in the prototype chain + * @param property the property + * @param desc the callsite descriptor + * @return method handle for guard + */ + public static MethodHandle getGuard(final ScriptObject sobj, final Property property, final CallSiteDescriptor desc) { + if (!needsGuard(property, desc)) { + return null; + } + if (NashornCallSiteDescriptor.isScope(desc)) { + if (property != null && property.isBound()) { + // This is a declared top level variables in main script or eval, use identity guard. + return getIdentityGuard(sobj); + } + if (!(sobj instanceof Global) && (property == null || property.isConfigurable())) { + // Undeclared variables in nested evals need stronger guards + return combineGuards(getIdentityGuard(sobj), getMapGuard(sobj.getMap())); + } + } + return getMapGuard(sobj.getMap()); + } + + + /** + * Get a guard that checks referential identity of the current object. + * + * @param sobj the self object + * @return true if same self object instance + */ + public static MethodHandle getIdentityGuard(final ScriptObject sobj) { + return MH.insertArguments(SAME_OBJECT, 1, new WeakReference<>(sobj)); + } + + /** * Get a guard that checks if in item is an instance of either of two classes. * * @param class1 the first class * @param class2 the second class * @return method handle for guard */ public static MethodHandle getInstanceOf2Guard(final Class<?> class1, final Class<?> class2) { return MH.insertArguments(IS_INSTANCEOF_2, 1, class1, class2); } + /** + * Combine two method handles of type {@code (Object)boolean} using logical AND. + * + * @param guard1 the first guard + * @param guard2 the second guard, only invoked if guard1 returns true + * @return true if both guard1 and guard2 returned true + */ + public static MethodHandle combineGuards(final MethodHandle guard1, final MethodHandle guard2) { + return MH.guardWithTest(guard1, guard2, MH.dropArguments(MH.constant(boolean.class, false), 0, Object.class)); + } + @SuppressWarnings("unused") private static boolean isScriptObject(final Object self) { return self instanceof ScriptObject; }
*** 99,108 **** --- 165,179 ---- private static boolean isMap(final Object self, final PropertyMap map) { return self instanceof ScriptObject && ((ScriptObject)self).getMap() == map; } @SuppressWarnings("unused") + private static boolean sameObject(final Object self, final WeakReference<ScriptObject> ref) { + return self == ref.get(); + } + + @SuppressWarnings("unused") private static boolean isInstanceOf2(final Object self, final Class<?> class1, final Class<?> class2) { return class1.isInstance(self) || class2.isInstance(self); } private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {