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

Nils Eliasson nils.eliasson at oracle.com
Wed Oct 28 16:12:46 UTC 2015

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.


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

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