RFR (S): 8140343: SEGV in DirectivesStack::getMatchingDirective

[Nils Eliasson]

Hi Vladimir,

The C1 store will always be an ok choice. Even if C1 is unavailable the 
c1 store will be populated with the common flags (Enable, Exclude, 
Print, Break, Log etc.).

I will update the comment to reflect that.

Thanks,
Nils


On 2015-10-28 16:19, Vladimir Kozlov wrote:
> I share Chris's concern - is _c1_store is always good choice and 
> always defined. We still can have Server VM without C1 (PPC64). Or 
> Zero. It should be taking into account.
>
> If _c1_store is always present in all VM variants - it should be 
> explained in comment.
>
> Thanks,
> Vladimir
>
> On 10/28/15 5:15 PM, Nils Eliasson wrote:
>> Still open for review.
>>
>> Regards,
>> Nils
>>
>> On 2015-10-24 10:49, Nils Eliasson wrote:
>>>
>>> On 2015-10-23 22:39, Christian Thalinger wrote:
>>>>> On Oct 22, 2015, at 11:03 PM, Nils Eliasson
>>>>> <nils.eliasson at oracle.com> wrote:
>>>>>
>>>>> Hi all,
>>>>>
>>>>> This fixes a bug when using a compiler that doesn't have compiler
>>>>> directives. This is a temporary fix using the default directive 
>>>>> for c1.
>>>> What are the default directives for C1 and C2?  This fix is for JVMCI
>>>> compilers and JVMCI compilers can only replace C2 in a tiered
>>>> configuration.  Depending on what they are, wouldn’t it make more
>>>> sense to use C2’s default directives?
>>>
>>> The default directive is a directive that is always installed, always
>>> enabled and contains all the default values from vmflags and compile
>>> commands. This is the directive all compilations are using if no
>>> additional directives are installed.
>>>>
>>>>> In the future permanent fix all compilers will have directives by
>>>>> default.
>>>> How would that look like?
>>>
>>> Long story. It is an internal implementation detail to the structure
>>> of compiler directives. Right now there is a bit of an overhead adding
>>> a new compiler, even if only a single flag is used. The idea is to
>>> have all directives contain all flags for all compilers - it might
>>> sound expensive but will actually be more efficient. The most common
>>> use case is only having the default directive, and in this case the
>>> common flags wouldn't have to be duplicated for each compiler. The
>>> profit in the JVMCI case is that all the common flags are valid and
>>> usable without any workaround. The improvement is straightforward and
>>> wont affect any use site but is big enough not to be the fix of this 
>>> bug.
>>>
>>> //Nils
>>>
>>>
>>>>> bug: https://bugs.openjdk.java.net/browse/JDK-8140343
>>>>> webrev: http://cr.openjdk.java.net/~neliasso/8140343/webrev.01/
>>>>>
>>>>> Please review,
>>>>> Nils
>>>
>>