Request for reviews (S): 6892186: 6896084: VM does not reserve protected page below heap for compressed oops implicit null checks

[Vladimir Kozlov]

I am taking this back. It will require adding
the cast in all expressions with this variable.
I will keep it as it was.

Vladimir

Vladimir Kozlov wrote:
> Thank you, Christian
> 
> I will change the type to address.
> 
> Vladimir
> 
> Christian Thalinger wrote:
>> On Wed, 2009-10-28 at 16:13 -0700, Vladimir Kozlov wrote:
>>> http://cr.openjdk.java.net/~kvn/6896084/webrev.00
>>>
>>> Fixed 6896084: VM does not reserve protected page below heap for 
>>> compressed oops implicit null checks
>>>
>>> Problem:
>>> VM should reserve protected page below heap for compressed oops
>>> implicit null checks in compiled code (see 6716785).
>>> After zero based compressed oops changes (6791178) the page is
>>> not reserved because undefined narrow_oop_base (NULL by default)
>>> is used in ReservedHeapSpace() to determine if the page is needed.
>>>
>>> Solution:
>>> Set narrow_oop_base and narrow_oop_use_implicit_null_checks
>>> values according to compressed oops encoding mode in
>>> Universe::preferred_heap_base() which is called before
>>> ReservedHeapSpace() constructors.
>>
>> Using size_t for base (which is an address) feels a little strange but
>> otherwise looks good.
>>
>> -- Christian
>>