RFR (S) 8013942: JSR 292: assert(type() == T_OBJECT) failed: type check

[serguei.spitsyn at oracle.com]

On 6/27/14 1:34 AM, serguei.spitsyn at oracle.com wrote:
> Hi Markus,
>
> I raised a good point, thanks!

Sorry, I wanted to say: "You raised a good point!" :)
> What do you think about increasing the predefined size (N from 2 to 4)?
>
>    64 class InterpreterOopMap: ResourceObj {
>    65   friend class OopMapCache;
>    66
>    67  public:
>    68   enum {
>    69     N                = 2,                // the number of words reserved
>    70                                          // for inlined mask storage
>    71     small_mask_limit = N * BitsPerWord,  // the maximum number of bits
>    72                                          // available for small masks,
>    73                                          // small_mask_limit can be set to 0
>    74                                          // for testing bit_mask allocation
>
>
> Thanks,
> Serguei
>
> On 6/27/14 1:12 AM, Markus Grönlund wrote:
>> Hi Serguei,
>>
>>
>> I am not convinced this is the right way to do this - by removing the #ifdef ENABLE_ZAP_DEAD_LOCALS" (which is an COMPILER2 specific #define under an ASSERT), we have now unconditionally increased the bitsize for every oopmap entry to two (compared to one previously) - the inlined oop_map bits_size cache is predefined to hold two words.
>>
>> This means the oopmap bitmap cache is effectively halved unconditionally.
>>
>> /Markus
>>
>>
>> -----Original Message-----
>> From: Serguei Spitsyn
>> Sent: den 27 juni 2014 00:15
>> To: Vladimir Ivanov;hotspot-dev at openjdk.java.net  Developers;serviceability-dev at openjdk.java.net
>> Subject: Re: RFR (S) 8013942: JSR 292: assert(type() == T_OBJECT) failed: type check
>>
>> Thanks, Vladimir!
>> Serguei
>>
>> On 6/26/14 3:02 PM, Vladimir Ivanov wrote:
>>> Looks good.
>>>
>>> Best regards,
>>> Vladimir Ivanov
>>>
>>> On 6/25/14 5:57 PM,serguei.spitsyn at oracle.com  wrote:
>>>> Please, review the fix for:
>>>>     https://bugs.openjdk.java.net/browse/JDK-8013942
>>>>
>>>>
>>>> Open webrev:
>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2014/hotspot/8013942-JVM
>>>> TI-lobj.1
>>>>
>>>>
>>>>
>>>>
>>>> Summary:
>>>>
>>>>     This is a Nightly Stabilization issue.
>>>>
>>>>     The problem is that the JVMTI GetLocalObject() function is hitting
>>>> the assert
>>>>     as the type of the local at current bci is not T_OBJECT as expected.
>>>>     It is because this local is alive only in a narrow scope of one
>>>> condition in the method but current bci is out of this csope.
>>>>
>>>>     A fragment from the target method:
>>>>
>>>>       static Class<?> canonicalize(Class<?> t, int how) {
>>>>           Class<?> ct; <== The local
>>>>           if (t == Object.class) {
>>>>               // no change, ever
>>>>           } else if (!t.isPrimitive()) {
>>>>               switch (how) {
>>>>                   case UNWRAP:
>>>>                       ct = Wrapper.asPrimitiveType(t); <== Initialized
>>>> here
>>>>                       if (ct != t) return ct;
>>>>                       break;
>>>>                   case RAW_RETURN:
>>>>                   case ERASE:
>>>>                       return Object.class;
>>>>               }
>>>>           } else if (t == void.class) {                <== The
>>>> GetLocalObject() is called with bci in this block
>>>>               // no change, usually
>>>>               switch (how) {
>>>>                   case RAW_RETURN:
>>>>                       return int.class;
>>>>                   case WRAP:
>>>>                       return Void.class;
>>>>               }
>>>>           } else {
>>>>           . . .
>>>>
>>>>     The local 'ct' is only alive in the block of condition "if
>>>> (!t.isPrimitive())".
>>>>     However, it is dead local in the next block.
>>>>
>>>>     The fix suggested in the webrev above is to use the oop_mask for
>>>> the method's current bci.
>>>>     It tells when the local is dead in the scope of this bci.
>>>>     Return the JVMTI_ERROR_INVALID_SLOT error in such a case.
>>>>
>>>>     The fix also includes the tweeks which are necessary to enable the
>>>> InterpreterOopMap.is_dead()
>>>>     function in the product mode as it was originally defined only
>>>> under "#ifdef ENABLE_ZAP_DEAD_LOCALS".
>>>>     This makes the code in the oopMapCache.?pp a little bit more simple.
>>>>
>>>>
>>>> Testing:
>>>>     Running the failing tests: vm.mlvm.indy.func.jvmti
>>>>     In progress: nsk.jvmti, nsk.jdi, nsk.jdwp test runs on sparcv9 and
>>>> amd64
>>>>
>>>>
>>>> Thanks,
>>>> Serguei
>>>>
>

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