RFR: 8220501: Improve c1_ValueStack locks handling

[Nils Eliasson]

+1

// Nils
> Hi Claes,
>
> looks good to me.
>
> Best regards,
> Tobias
>
> On 12.03.19 13:52, Claes Redestad wrote:
>> Hi,
>>
>> the _locks Values in ValueStack is often empty/unused, and allocating it
>> lazily is a small startup/warmup optimization.
>>
>> Webrev: http://cr.openjdk.java.net/~redestad/8220501/open.00/
>> Bug:    https://bugs.openjdk.java.net/browse/JDK-8220501
>>
>> Testing: tier1-3
>>
>> Thanks!
>>
>> /Claes