RFR: 8217922: Compiler dead code removal

[Claes Redestad]

Hi,

please review this patch to remove dead code in the compiler area.

Bug:    https://bugs.openjdk.java.net/browse/JDK-8217922
Webrev: http://cr.openjdk.java.net/~redestad/8217922/open.00/

Testing: tier1+2

I've taken care to check every change to ensure it's not in use by some
platform specific code on a platform that's not built/supported by
Oracle, but help verifying this would be greatly appreciated.

I've also checked the patch applies cleanly to a few valhalla and amber
branches to avoid excessive merge issues.

Thanks!

/Claes