[10] RFR(M): 8176506: C2: loop unswitching and unsafe accesses cause crash

[Vladimir Kozlov]

Can use SIGILL (illegal instruction) on all platforms? It should be correctly processed on all platforms and generate 
hs_err file.

Vladimir

On 5/4/17 9:04 AM, Roland Westrelin wrote:
>
> Hi Volker,
>
> Thanks for looking at this and trying it.
>
>> I obviously prefer the first crash, so maybe you can at least only
>> change the platforms which called "breakpoint()" until now?
>
> I thought making the implementation consistent across platforms was
> worthwhile but I don't have a strong opinion on this. I won't have to
> troubleshoot failures on sparc so whatever works for those who do is
> fine with me. What do you think, Vladimir?
>
>> Not sure if this is easily possible, but I think an ideal solution
>> would be to really execute the actual, offending load instead of
>> inserting a HaltNode. That would give you a nice hs_err file on all
>> platforms where the registers would even contain the offending address
>> (NULL) and the offset. I think this could simplify troubleshooting in
>> the case of a crash. What do you think?
>
> It's not possible with the current implementation. We would need to turn
> the Halt into an uncommon trap. My reasoning was that if we were about
> to crash we could as well crash right away. It's true it could make
> troubleshooting harder. Note that trying to read an object field off
> heap is another bad scenario that would trigger a Halt but it might not
> crash if run interpreted. Let's say we uncommon trap instead of crash in
> that case, what do we do if we hit that unc several times?
>
> Roland.
>