RFR(S): 8029351: assert(bt != T_OBJECT) failed: Guard is incorrect in VM:defmeth

[David Chase]

Do you think it's worth changing for this one?
I'm a little mystified at how this interacts with process at this stage.

David

On 2013-12-08, at 1:25 PM, Christian Thalinger <christian.thalinger at oracle.com> wrote:

> It would only be used once but I think it would be a good idea to move the "is this an object?” test into a method in constantTag.  That way the checks would have a descriptive name and be co-located with the other tags.  Might help to avoid bugs like this in the future.
> 
> The fix looks good.
> 
> On Dec 7, 2013, at 7:12 PM, David Chase <david.r.chase at oracle.com> wrote:
> 
>> RT-dev CC'd because this was more of a runtime bug, except that involved methodHandles.
>> 
>> bug: https://bugs.openjdk.java.net/browse/JDK-8029351
>> webrev: http://cr.openjdk.java.net/~drchase/8029351/webrev.01/
>> 
>> Running "defmeth", especially with -Xcomp and -XX:+AggressiveOpts, sometimes (1 in 25 to 1 in 50)
>> causes a crash in fastdebug, that in release builds is instead a signal-ignoring infinite loop.
>> 
>> The cause was failure to include the method_handle_in_error and method_type_in_error
>> cases in the "is this an object?" test.  This immediately led to a blown assertion in a debug build.
>> Fix was to add the obvious clauses to the if:
>> 
>>      tag.is_unresolved_klass() ||
>>      tag.is_string() ||
>>      tag.is_method_handle() ||
>> -      tag.is_method_type()) {
>> +      tag.is_method_type() ||
>> +      tag.is_method_handle_in_error() ||
>> +      tag.is_method_type_in_error()) {
>>    assert(bt == T_OBJECT, "Guard is incorrect");
>>    cts = CellTypeState::make_line_ref(bci);
>>  } else {
>> 
>> Testing:
>> defmeth, fastdebug build with bug-provoking flags , 1000 times.
>> All ran w/o crash (i.e., only with other existing known failures), all produced the same output.
>> 
>> David
>> 
> 

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 801 bytes
Desc: Message signed with OpenPGP using GPGMail
Url : http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/attachments/20131208/5da96dc1/signature.asc