RFR: 8254793: [JVMCI] improve speculation encoding [v4]

[Vladimir Kozlov]

On Fri, 16 Oct 2020 16:33:20 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> This PR changes the encoding of a `jdk.vm.ci.hotspot.HotSpotSpeculationLog.HotSpotSpeculation` from a long to an int.
>> The `Thread::_pending_failed_speculation` field remains as a `jlong` since it is already exposed to JVMCI Java code
>> already via VMStructs and this PR does not update its usage in Graal.
>
> Doug Simon has refreshed the contents of this pull request, and previous commits have been removed. The incremental
> views will show differences compared to the previous content of the PR. The pull request contains one new commit since
> the last revision:
>   8254793: encode a HotSpotSpeculation in 31 bits

Good.

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Marked as reviewed by kvn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/667