RFR: 8287700: C2 Crash running eclipse benchmark from Dacapo

[Roland Westrelin]

On Tue, 7 Jun 2022 14:57:07 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> With 8275201 (C2: hide klass() accessor from TypeOopPtr and typeKlassPtr subclasses), I made the following change to escape.cpp:
>> 
>> 
>> @@ -2628,7 +2632,7 @@ bool ConnectionGraph::split_AddP(Node *addp, Node *base) {
>>    // this code branch will go away.
>>    //
>>    if (!t->is_known_instance() &&
>> -      !base_t->klass()->is_subtype_of(t->klass())) {
>> +      !t->maybe_java_subtype_of(base_t)) {
>>       return false; // bail out
>>    }
>>    const TypeOopPtr *tinst = base_t->add_offset(t->offset())->is_oopptr();
>> @@ -3312,7 +3316,7 @@ void ConnectionGraph::split_unique_types(GrowableArray<Node *>  &alloc_worklist,
>>          } else {
>>            tn_t = tn_type->isa_oopptr();
>>          }
>> -        if (tn_t != NULL && tinst->klasgs()->is_subtype_of(tn_t->klass())) {
>> +        if (tn_t != NULL && tn_t->maybe_java_subtype_of(tinst)) {
>>            if (tn_type->isa_narrowoop()) {
>>              tn_type = tinst->make_narrowoop();
>>            } else {
>> @@ -3325,7 +3329,7 @@ void ConnectionGraph::split_unique_types(GrowableArray<Node *>  &alloc_worklist,
>>            record_for_optimizer(n);
>>          } else {
>>            assert(tn_type == TypePtr::NULL_PTR ||
>> -                 tn_t != NULL && !tinst->klass()->is_subtype_of(tn_t->klass()),
>> +                 tn_t != NULL && !tinst->is_java_subtype_of(tn_t),
>>                   "unexpected type");
>>            continue; // Skip dead path with different type
>>          }
>> 
>> 
>> Where I inverted the subtype and supertype in a subtype check (that is `tn_t->maybe_java_subtype_of(tinst)` when it was `tinst->klasgs()->is_subtype_of(tn_t->klass())`) in 2 places for no good reason AFAICT now. The assert used to also test the same condition as the if above but I changed that by mistake. This fixes addresses both issues.
>
> That looks good to me.

@chhagedorn @vnkozlov @navyxliu @TobiHartmann thanks for the reviews

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PR: https://git.openjdk.java.net/jdk/pull/9054