6894807: problem with interfaces in C2 type system (original) (raw)

Vladimir Kozlov Vladimir.Kozlov at Sun.COM
Fri Oct 23 21:50:51 PDT 2009

I am investigating 6894807: No ClassCastException for HashAttributeSet constructors if run with -Xcomp

Because of Escape Analysis is on by default all constructors are inlined in the test case and object scalar replaced. But due to, I think, the problem in C2 type system the result is incorrect.

We should check if interface is exact before replacing it with j.l.O in TypeOopPtr::filter() for the case (exact interface)->filter(j.l.O).

Vladimir

Test code expects ClassCastException exception:

import javax.print.attribute.Attribute; import javax.print.attribute.AttributeSet; import javax.print.attribute.DocAttribute; import javax.print.attribute.HashAttributeSet; import javax.print.attribute.standard.JobState;

     try {
         new MyHashAttributeSet(JobState.CANCELED, DocAttribute.class);
         System.out.println("No ClassCastException in t2!");
     } catch (ClassCastException _) {
     }

EA forces to inline all constructors for MyHashAttributeSet:

class MyHashAttributeSet extends HashAttributeSet{ MyHashAttributeSet(Attribute attribute, Class interfaceName){ super(attribute, interfaceName); }

then

 protected HashAttributeSet(Attribute attribute, Class<?> interfaceName) {
     if (interfaceName == null) {
         throw new NullPointerException("null interface");
     }
     myInterface = interfaceName;
     add (attribute);
 }

add() is inlined also:

 public boolean add(Attribute attribute) {
     Object oldAttribute =
         attrMap.put(attribute.getCategory(),
                     AttributeSetUtilities.
                     verifyAttributeValue(attribute, myInterface));
     return (!attribute.equals(oldAttribute));
 }

and verifyAttributeValue(attribute, myInterface) is inlined as well:

 public static Attribute
     verifyAttributeValue(Object object, Class<?> interfaceName) {

     if (object == null) {
         throw new NullPointerException();
     }
     else if (interfaceName.isInstance (object)) {
         return (Attribute) object;
     } else {
         throw new ClassCastException();
     }
 }

object is JobState.CANCELED which is

 public static final JobState CANCELED = new JobState (7);

and interfaceName is DocAttribute.class where

public interface DocAttribute extends Attribute {}

So we end up with

(DocAttribute.class).isInstance(JobState.CANCELED)

We have intrinsic for isInstance() for which we generated

// Now load the mirror's klass metaobject, and null-check it. // Side-effects region with the control path if the klass is null. Node* kls = load_klass_from_mirror(mirror, never_see_null, nargs, region, _prim_path);

case vmIntrinsics::_isInstance: // nothing is an instance of a primitive type query_value = gen_instanceof(obj, kls);

where due to NULL check we have next CastPP for DocAttribute.class: [t at 19 l at 19]: print kls->dump(1) 390 LoadKlass === _ 7 389 [[ 391 396 ]] @rawptr:BotPTR, idx=Raw; # * Klass: * !jvms: AttributeSetUtilities::verifyAttributeValue @ bci:14 HashAttributeSet::add @ bci:15 HashAttributeSet:: @ bci:36 MyHashAttributeSet:: @ bci:3 InstanceCheck::t2 @ bci:10 395 IfTrue === 393 [[ 370 396 ]] #1 !jvms: AttributeSetUtilities::verifyAttributeValue @ bci:14 HashAttributeSet::add @ bci:15 HashAttributeSet:: @ bci:36 MyHashAttributeSet:: @ bci:3 InstanceCheck::t2 @ bci:10 396 CastPP === 395 390 [[ 409 409 413 432 427 ]] #klass java/lang/Object: 0x0811c7e0 * Klass:klass java/lang/Object: 0x0811c7e0 * !jvms: AttributeSetUtilities::verifyAttributeValue @ bci:14 HashAttributeSet::add @ bci:15 HashAttributeSet:: @ bci:36 MyHashAttributeSet:: @ bci:3 InstanceCheck::t2 @ bci:10

During IGVN LoadKlass(390) transformed to constant klass which is interface:

702 ConP === 0 [[ 396 391 ]] #precise klass javax/print/attribute/DocAttribute: 0x08407298:Constant:exact * Interface:precise klass javax/print/attribute/DocAttribute: 0x08407298:Constant:exact * 396 CastPP === 395 702 [[ 409 409 413 432 427 ]] #klass java/lang/Object: 0x0811c7e0 * Klass:klass java/lang/Object: 0x0811c7e0 * !jvms: AttributeSetUtilities::verifyAttributeValue @ bci:14 HashAttributeSet::add @ bci:15 HashAttributeSet:: @ bci:36 MyHashAttributeSet:: @ bci:3 InstanceCheck::t2 @ bci:10

ConstraintCastNode::Value() calls TypeOopPtr::filter() method which, I think, returns incorrect result:

[t at 19 l at 19]: print ft->dump() precise klass javax/print/attribute/DocAttribute: 0x08407298:Constant:exact *

[t at 19 l at 19]: print ftkp->klass()->print()

[t at 19 l at 19]: print ktkp->klass()->print() ktkp->klass()->print() = (void)

because of this code:

// If we have an interface-typed Phi or cast and we narrow to a class type, // the join should report back the class. However, if we have a J/L/Object // class-typed Phi and an interface flows in, it's possible that the meet & // join report an interface back out. This isn't possible but happens // because the type system doesn't interact well with interfaces.

if (ftkp != NULL && ktkp != NULL && ftkp->is_loaded() && ftkp->klass()->is_interface() && ktkp->is_loaded() && !ktkp->klass()->is_interface()) { // Happens in a CTW of rt.jar, 320-341, no extra flags return ktkp->cast_to_ptr_type(ftkp->ptr()); }

the result is

precise klass java/lang/Object: 0x0811c7e0:Constant:exact *

which leads to incorrect result from CmpP node:

703 ConP === 0 [[ 704 432 704 ]] #precise klass java/lang/Object: 0x0811c7e0:Constant:exact * Klass:precise klass java/lang/Object: 0x0811c7e0:Constant:exact * 704 CmpP === _ 703 703 [[ 705 ]] !orig=[413] !jvms: AttributeSetUtilities::verifyAttributeValue @ bci:14 HashAttributeSet::add @ bci:15 HashAttributeSet:: @ bci:36 MyHashAttributeSet:: @ bci:3 InstanceCheck::t2 @ bci:10

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