6894807: problem with interfaces in C2 type system
John Rose
John.Rose at Sun.COM
Mon Oct 26 22:07:07 PDT 2009
Ughh. We keep patching this stuff...
Two questions:
1. Is the second occurrence of this comment really true, or is it just
a copy of the first occurrence (from Tom's fix)?
// Happens in a CTW of rt.jar, 320-341, no extra flags
2. Why doesn't the bug happen in the original code? Oh, right: An
object cannot have exactly an interface type.
It's strange to have a phi with a constant type. Maybe the right
answer for a filter() query is, if the phi's type ('kill' arg) is a
Type::singleton, return it without further processing.
-- John
On Oct 26, 2009, at 8:30 PM, Vladimir Kozlov wrote:
> Thanks, Tom
>
> I will do it.
>
> Vladimir
>
> Tom Rodriguez wrote:
>> I think it should include an extra test of !ftkp->klass_is_exact
>> (). 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->cast_to_ptr_type(ftkp->ptr());
>>>
>>> The fix is either simple return original j.l.o klass:
>>>
>>> return kills;
>>>
>>> or cast to ptrs meet:
>>>
>>> return ktkp->cast_to_ptr_type(ktkp->meet_ptr(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 = 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::<init> @ bci:36
>>>> MyHashAttributeSet::<init> @ bci:3 InstanceCheck::t2 @ bci:10
>>>> 395 IfTrue === 393 [[ 370 396 ]] #1 !jvms:
>>>> AttributeSetUtilities::verifyAttributeValue @ bci:14
>>>> HashAttributeSet::add @ bci:15 HashAttributeSet::<init> @ bci:36
>>>> MyHashAttributeSet::<init> @ 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::<init> @ bci:36
>>>> MyHashAttributeSet::<init> @ 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::<init> @ bci:36
>>>> MyHashAttributeSet::<init> @ 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()
>>>> <ciInstanceKlass name=javax/print/attribute/DocAttribute
>>>> loader=0x0 loaded=true initialized=false finalized=false
>>>> subklass=false size=9 flags=public,interface,abstract
>>>> mirror=PRESENT ident=655 PERM address=0x8407298>
>>>> [t at 19 l at 19]: print ktkp->klass()->print()
>>>> <ciInstanceKlass name=java/lang/Object loader=0x0 loaded=true
>>>> initialized=true finalized=false subklass=true size=8
>>>> flags=public,super mirror=PRESENT ident=558 PERM
>>>> address=0x811c7e0>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::<init> @ bci:36
>>>> MyHashAttributeSet::<init> @ bci:3 InstanceCheck::t2 @ bci:10
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