RFR: Several C1 cleanups

[Roman Kennke]

Am 11.07.2018 um 10:19 schrieb Aleksey Shipilev:
> On 07/10/2018 10:34 PM, Roman Kennke wrote:
>> http://cr.openjdk.java.net/~rkennke/c1cleanup/webrev.00/
> 
> Looks good.
> 
> This patch looks backportable to sh/jdk11, but not further?

It depends on "Consolidate assembly write barriers". This is not trivial
to do in jdk10 because it depends on generating the WB stubs before
interpreter. I guess it's possible but tricky, and probably not worth.

Roman