RFR: 8217747: ZGC: Minor optimization of ZLoadBarrierStubC1

[Nils Eliasson]

Looks good,

// Nils

On 2019-01-28 09:56, Per Liden wrote:
> In the C1 load barrier stub for ZGC we currently save/restore rax 
> unless it's the stub result register. However, we can also avoid this 
> save/restore of rax if it's the tmp register. Avoiding a push/pop in 
> the stub isn't really an important optimization, but since we already 
> do it for the result register we can just as well do it for the tmp 
> register too, without making the code more complex.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8217747
> Webrev: http://cr.openjdk.java.net/~pliden/8217747/webrev.0
>
> /Per