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

Vladimir Kozlov Vladimir.Kozlov at Sun.COM
Mon Oct 26 17:30:14 PDT 2009

Thanks, Tom

I will do it.

Vladimir

Tom Rodriguez wrote:

I think it should include an extra test of !ftkp->klassisexact(). This will cause it to return ft which is the original precise type.

tom On Oct 26, 2009, at 3:07 PM, Vladimir Kozlov wrote:

John, Tom

I need your help with this. The original implementation of TypeOopPtr::filter() was done by John and pushed by Ross for: 6467870: Fixes to monotonically narrow or widen types during igvn Ross Knippel wrote: > This change is from John Rose (I'm just the medium.) > It's a piece extracted from his current work. It did not have the bug's problem since an interface could not be exact. Then Tom added the klass part for: 6788347: C2Compiler crash 6u7 Which causes the problem since interface klass could be exact (constant, as in the bug's case) and casting j.l.O klass to interface's ptr returns incorrectly exact j.l.O klass: return ktkp->casttoptrtype(ftkp->ptr()); The fix is either simple return original j.l.o klass: return kills; or cast to ptrs meet: return ktkp->casttoptrtype(ktkp->meetptr(ftkp->ptr())); Both of them fixed the problem. But I am not sure since in both cases we loose the precision of interface klass which allows more ideal optimizations (for example, for CmpP). Thanks, Vladimir Vladimir Kozlov wrote: 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 klass)->filter(j.l.O klass). 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 = loadklassfrommirror(mirror, neverseenull, nargs, region, primpath); case vmIntrinsics::isInstance: // nothing is an instance of a primitive type queryvalue = geninstanceof(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->isloaded() && ftkp->klass()->isinterface() && ktkp->isloaded() && !ktkp->klass()->isinterface()) { // Happens in a CTW of rt.jar, 320-341, no extra flags return ktkp->casttoptrtype(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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