RFR(S): 8227597: [fastdbg build] Arena::inc_bytes_allocated should get inlined

[Doerr, Martin]

Hi,

the simple function Arena::inc_bytes_allocated can be found as CPU consuming when profiling the fastdbg build. It is located in a cpp file.
It should better get inlined to improve the performance of the fastdbg VM which is important for complex tests.
In addition, atomic 8-Byte load and store functions are available on all platforms, so the "#if defined ..." can get removed.

Here's my proposal:
http://cr.openjdk.java.net/~mdoerr/8227597_DBG_Inline_inc_bytes_allocated/webrev.00/

Feedback is welcome.

Best regards,
Martin