RFR: Merge shenandoah:genshen

[earthling-amzn]

On Fri, 12 Feb 2021 19:02:36 GMT, earthling-amzn <github.com+71722661+earthling-amzn at openjdk.org> wrote:

>> This is impossible to actually review, so I'm limited to testing it:
>> it finds the following compilation failure. It's probably lacking in include there. Make sure to test with --disable-precompiled-headers.
>> 
>> === Output from failing command(s) repeated here ===
>> * For target hotspot_variant-server_libjvm_objs_BUILD_LIBJVM_link:
>> 
>> 
>> collect2: error: ld returned 1 exit status
>> 
>> * All command lines available in /home/rkennke/src/openjdk/shenandoah/build/linux-x86_64-server-fastdebug/make-support/failure-logs.
>> === End of repeated output ===
>
> Taking a look now. The bot suggests changing the title of this PR to indicate that it's a merge, otherwise it will be squashed. If this gets squashed, won't it make subsequent merges from master more difficult? Is it okay with you if I change the title of this PR so this goes into a `genshen` as a merge and not a giant squashed commit?

Well, the bot doesn't like having this PR titled as a "merge".

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PR: https://git.openjdk.java.net/shenandoah/pull/14