RFR: 8252406: Introduce Thread::as_Java_thread() convenience function [v2]

[Kim Barrett]

> On Sep 8, 2020, at 12:09 AM, David Holmes <dholmes at openjdk.java.net> wrote:
> David Holmes has updated the pull request incrementally with one additional commit since the last revision:
> 
>  Used static_cast instead of raw C-style cast
>  Moved inline functions to thread.inline.hpp
>  Updated #includes to deal with the move to thread.inline.hpp
>  Updated copyright year where needed.
> 
> -------------
> 
> Changes:
>  - all: https://git.openjdk.java.net/jdk/pull/37/files
>  - new: https://git.openjdk.java.net/jdk/pull/37/files/b18faad5..da70f804
> 
> Webrevs:
> - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=37&range=01
> - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=37&range=00-01
> 
>  Stats: 102 lines in 33 files changed: 39 ins; 28 del; 35 mod
>  Patch: https://git.openjdk.java.net/jdk/pull/37.diff
>  Fetch: git fetch https://git.openjdk.java.net/jdk pull/37/head:pull/37
> 
> PR: https://git.openjdk.java.net/jdk/pull/37

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src/hotspot/share/runtime/thread.hpp
 507   const JavaThread* as_const_Java_thread() const;

This missed part of what I'd suggested. I don't think the "const" part
of the name is needed or helpful.  Just overload as_Java_thread on the
const-ness of the thread it's being applied to.

There are some situations where there is such an overload pair and it
is useful to additionally have an explicit const function, but I don't
think this is one of those.

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The fannout from putting the conversion functions in thread.inline.hpp seems
pretty high in the number of files that get touched. Especially since it
leads to JavaThread::current() and JavaThread::as_CompilerThread() being
moved. I would have been at least fine with, and probably would prefer,
having the definitions of as_JavaThread near the old definitions of those
functions in thread.hpp.

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