[9] RFR(S): 8136458: Remove "marked for reclamation" nmethod state

[Tobias Hartmann]

Hi,

please review the following patch.

https://bugs.openjdk.java.net/browse/JDK-8136458
http://cr.openjdk.java.net/~thartmann/8136458/webrev.00/

The sweeper removes zombie nmethods only after they were "marked for reclamation" to ensure that there are no inline caches referencing the zombie nmethod. However, this is not required because if a zombie nmethod is encountered again by the sweeper, all ICs pointing to it were already cleaned in the previous sweeper cycle:

alive -> not-entrant/unloaded (may be on the stack)
cycle 1: not-entrant/unloaded -> zombie (may be referenced by ICs)
cycle 2: zombie -> marked for reclamation
cycle 3: marked for reclamation -> flush

In each cycle, we clean all inline caches that point to not-entrant/unloaded/zombie nmethods. Therefore, we know already after sweeper cycle 2, that the zombie nmethod is not referenced by any ICs and we could flush it immediately.

I removed the "marked for reclamation" state. The following testing revealed no problems:
- JPRT
- RBT with hotspot_all and -Xcomp/-Xmixed
- 100 iterations of Nashorn + Octane with -XX:StartAggressiveSweepingAt=100/50 -XX:NmethodSweepActivity=500/100

Thanks,
Tobias