RFR: JDK-8237780: Shenandoah: More reliable nmethod verification

[Roman Kennke]

Hi Aleksey,

>> I've also left in some debug-output but under #ifdef ASSERT_DISABLED. I
>> found that very useful and wouldn't want to throw it away.
> 
> I think the proper way to do this is:
> 
>  #if 0 // Helpful for debugging
> 
> ...but then I wonder, why not turn it into the actual fastdebug diagnostics? Our verifier/asserts
> very helpfully include a lot of debugging info into hs_err when asserts fail. Surely if we are
> chasing a very rare bug, it would be more convenient for hs_err to include that right away, not
> require us recompile the VM.

Right, let's leave it there for diagnostics.

>> Webrev:
>> http://cr.openjdk.java.net/~rkennke/JDK-8237780/webrev.00/
> 
> *) Looks like you can just initialize "int count = _oop_count" and skip increments in the first loop.

Right.

> *) Capitalization in "Must", to match the style of other asserts:
> 
>  305     assert(nm == data->nm(), "must be same nmethod");

Ok.

> *) assert(false, ...) is probably just fatal(...)

Ok.

http://cr.openjdk.java.net/~rkennke/JDK-8237780/webrev.01/

Good now?

Thanks,
Roman