RFR: Save both IU and FPU state in WB stub around runtime call

[Roman Kennke]

Hi Aleksey,

> On 11/20/18 2:19 PM, Roman Kennke wrote:
>> http://cr.openjdk.java.net/~rkennke/fixwbstub/webrev.00/
> 
> *) It is unfortunate we have to restore %rax and do the RB part of WB on this path. I don't see an
> easy way out, though. Please put the comment near RB on rax:
>   // Need to restore the WB result, which have to be the forwarded object.

The alternative would easy but ugly in other ways: do what we do now,
i.e. push all (GP) registers one after the other, do the FPU parts with
push_FPU_state() and pop_FPU_state(), and pop the GP registers in
reverse order, except %rax. What would you prefer?


Roman