RFR (S) 8212956: [JVCMI] SpeculationReason should maintain identity

[Vladimir Kozlov]

Looks good.

Vladimir

On 10/25/18 10:36 AM, Tom Rodriguez wrote:
> http://cr.openjdk.java.net/~never/8212956/webrev
> https://bugs.openjdk.java.net/browse/JDK-8212956
> 
> The changes for JDK-8205824 introduced a level of indirection in the Speculation implementation for JVMCI but lost some 
> identity along the way. Speculating on the same SpeculationReason multiple times should result in an equivalent 
> Speculation and JavaConstant encoding to avoid unnecessary duplication of uncommon traps.  Tested with new unit test and 
> graal gates.
> 
> tom