RFR: Filter out not compilable methods to avoid false assertion

[Aleksey Shipilev]

On 08/02/2018 08:44 PM, Zhengyu Gu wrote:
> Compiler actually encounters some methods that are not compilable, such as methods having
> breakpoints set or being redefined, they should be filtered out, cause they are not really gotten
> compiled.
> 
> Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/filter_bad_method/webrev.00/

Looks good. Please swap the operands in condition, so they line up like below, and push.

  guarantee(... || !target_compilable || (compilable != ciEnv::MethodCompilable_not_at_tier))
...
  guarantee(... || !target_compilable || (compilable != ciEnv::MethodCompilable_never))

-Aleksey