[9] RFR(S): 8066763: fatal error "assert(false) failed: unexpected yanked node" in postaloc.cpp:139

[Tobias Hartmann]

Thanks, Vladimir.

I renamed the variable to 'in':

http://cr.openjdk.java.net/~thartmann/8066763/webrev.01/

Best,
Tobias

On 11.12.2014 10:28, Vladimir Kozlov wrote:
> Looks good but rename local from 'req' (required) to 'in' (input) or 'dead'.
> 
> Thanks,
> Vladimir
> 
> On 12/11/14 1:14 AM, Tobias Hartmann wrote:
>> Hi,
>>
>> please review the following patch.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8066763
>> Webrev: http://cr.openjdk.java.net/~thartmann/8066763/webrev.00/
>>
>> Problem:
>> A null check for an oop loaded by a LoadNNode (300) consists of a CmpNNode
>> (388), a BoolNode (356) and a IfNode (357) [1].
>> After matching, the CmpNNode is replaced by a testN_reg node (56) and a jmpCon
>> node (55) [2]. With implicit null checks enabled (default), the compiler notices
>> that the oop is accessed by a nearby loadINode (131) and optimizes the code by
>> using an implicit null check: Instead of checking the oop explicitly, the
>> loadINode is moved upwards and executed without a check. Code is added to handle
>> the SIGSEGV and throw the corresponding NullPointerException [3].
>>
>> The problem is that after the optimization the testN_reg node is dead (see [3])
>> and triggers the assert in the register allocator. With implicit null checks
>> disabled (-XX:-ImplicitNullChecks) the bug does not appear.
>>
>> Solution:
>> The proposed fix checks for dead input nodes after removing the old compare
>> node. This removes the dead testN_reg node (see [4]).
>>
>> Testing:
>> - Failing test
>> - JPRT
>>
>> Thanks,
>> Tobias
>>
>> [1] https://bugs.openjdk.java.net/secure/attachment/24158/1_before_matching.png
>> [2]
>> https://bugs.openjdk.java.net/secure/attachment/24187/2_global_code_motion.png
>> [3]
>> https://bugs.openjdk.java.net/secure/attachment/24159/1_global_code_motion.png
>> [4]
>> https://bugs.openjdk.java.net/secure/attachment/24161/3_global_code_motion.png
>>