[13] RFR(S): 8224658: Unsafe access C2 compile fails with assert(flat != TypePtr::BOTTOM) failed: cannot alias-analyze an untyped ptr: adr_type = NULL

[Tobias Hartmann]

Getting back to this.

I've added additional tests that trigger constant folding of the address to NULL only after parsing
with incremental inlining. This triggers the same assert during final graph reshaping. New code in
MemNode::Ideal_common will detect this, cut of control and add a HaltNode to fail if this is ever
executed (we will fail with a SIGILL).

I've also fixed a missing 'unsafe' argument being passed on in graphKit.hpp.

http://cr.openjdk.java.net/~thartmann/8224658/webrev.01/

Thanks,
Tobias

On 23.05.19 15:21, Tobias Hartmann wrote:
> Hi Vladimir,
> 
> thanks for looking at this.
> 
> On 23.05.19 15:09, Vladimir Ivanov wrote:
>> The fix should work fine for Unsafe.getXxx(0) case, but what if address turns into 0 later? For
>> example, I don't see a reason why it can't theoretically happen in presence of post-parse inlining
>> happening in effectively unreachable code.
> 
> Yes that's possible and I thought it doesn't matter because we won't hit that assert during IGVN.
> I've just checked in detail and C2 actually completely removes the unsafe access in that case which
> is obviously incorrect.
> 
> I'll come back once I have a fix ready.
> 
> Thanks,
> Tobias
>