[15] RFR: 8237894: CTW: C1 compilation fails with assert(x->type()->tag() == f->type()->tag()) failed: should have same type

[Tobias Hartmann]

On 17.02.20 13:34, Jamsheed C M wrote:
> i meant for null object field access or indexed access, the instruction can match across subtypes* 
> and get eliminated. which can still put us in awkward situation if we try checking exact/declared
> types, which we normally don't do.
> 
> *(as instruction types are erased types)

Right but it's not a problem with current code.

>>>> And given that, does your solution actually work with Object arrays?
>>> Yes, as we are asserting on elem instruction type for indexed access.
>> But isn't it the case that with your change, a null from an MyObject1[] load still has the same hash
>> as a null from a MyObject2[] load because type()->tag() is the same? And wouldn't that still trigger
>> the assert?
> it wouldn't, instruction types are erased types. so sub types all would match

Okay, I see. Thanks for the explanation.

Webrev.01 seems reasonable to me but I think it would be good if someone with more C1 expertise
could take a look as well.

Thanks,
Tobias