RFR(S): 8189616: [s390] Remove definition and all uses of STCK instruction

[Schmidt, Lutz]

Dear all,

I would like to request reviews for this s390-only bug fix:

Bug:    https://bugs.openjdk.java.net/browse/JDK-8189616
Webrev: http://cr.openjdk.java.net/~lucy/webrevs/8189616.00/index.html

STCK is an ancient instruction to store a CPU timer value. It guarantees strict monotonicity of the stored values across all CPUs in a system. The inherent synchronization has a performance impact which becomes “considerable” (according to IBM specialists) with the recently announced processor generation (z14).

This change removes the STCK instruction from s390 platform code. The intent is to prevent inadvertent use of the instruction.

Thank you!
Lutz


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