RFR: 8250825: C2 crashes with assert(field != __null) failed: missing field

[jiefu(傅杰)]

Hi Vladimir K,

Thanks for your review.

The test had been extended here:
  - http://cr.openjdk.java.net/~jiefu/8250825/webrev.01/

Before the patch:
  The unsafe access (put/get) to static field will crash.
  The unsafe access (put/get) to instance field is fine.

After the patch:
  All is ok.

Thanks a lot.
Best regards,
Jie

On 2020/7/31, 2:24 AM, "hotspot-compiler-dev on behalf of Vladimir Kozlov" <hotspot-compiler-dev-retn at openjdk.java.net on behalf of vladimir.kozlov at oracle.com> wrote:

    Hi Jie
    
    Nodes generated by make_unsafe_address() are correct. The issue is that Unsafe API allows to genereate unaligned (to 
    fields) offset with arbitrary type. As result C2 type system can't find corresponding field.
    
    Did you tried to do unaligned unsafe access to instance fields?
    Also try to unsafe set value (Store node). There is code in C2 which checks for narrow stores. Would be interesting how 
    it behave in unsafe case.
    
    Please, extend your test.
    
    Otherwise fix is good.
    
    Thanks,
    Vladimir K
    
    On 7/30/20 6:09 AM, jiefu(傅杰) wrote:
    > Hi all,
    > 
    > JBS:    https://bugs.openjdk.java.net/browse/JDK-8250825
    > Webrev: http://cr.openjdk.java.net/~jiefu/8250825/webrev.00/
    > 
    > When C2 tries to inline an unsafe-access method, it may generate the following pattern in make_unsafe_address:
    >        ConP  ConL
    >           \  |
    >            \ |
    >            AddP
    > Current implementation of TypeOopPtr::TypeOopPtr(...) failed to recognize it as an unsafe operation, which leads to the crash.
    > 
    > Testing:
    >    - tier1-3 on Linux/x64
    > 
    > Could you please review it and give me some advice?
    > 
    > Thanks a lot.
    > Best regards,
    > Jie
    >