Integrated: 8247909: Improve PrimitiveConversions::cast using C++14

[Kim Barrett]

On Sun, 13 Sep 2020 07:27:13 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Please review this reimplementation of PrimitiveConversions::cast,
> using facilities from C++14.  In particular, conversions involving
> only integral values or integral and enum values are now constexpr.
> Also using <type_traits> rather than HotSpot work-alikes.
> 
> Had to update zForwardingEntry.hpp because of a class no longer being
> implicitly included.  Improved a friend declaration while in the
> vicinity.
> 
> Testing
> mach5 tier1

This pull request has now been integrated.

Changeset: 7eb4d4aa
Author:    Kim Barrett <kbarrett at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/7eb4d4aa
Stats:     241 lines in 4 files changed: 111 ins; 113 del; 17 mod

8247909: Improve PrimitiveConversions::cast using C++14

Reimpliment PrimitiveConversions::cast, with some cases now constexpr.
<!-- Anything below this marker will be automatically updated, please do not edit manually! -->
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### Progress
- [x] Change must not contain extraneous whitespace
- [x] Commit message must refer to an issue
- [ ] Change must be properly reviewed

### Issue
* [JDK-8247909](https://bugs.openjdk.java.net/browse/JDK-8247909): Improve PrimitiveConversions::cast using C++14


### Download
`$ git fetch https://git.openjdk.java.net/jdk pull/143/head:pull/143`
`$ git checkout pull/143`

Reviewed-by: dholmes, stefank

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PR: https://git.openjdk.java.net/jdk/pull/143