[OpenJDK 2D-Dev] RFR: 8246032: Implementation of JEP 347: Adopt C++14 Language Features in HotSpot

[Kim Barrett]

[Changes are only to the build system, but since the changes have jdk-wide
effect I’ve cc’d what I think are the relevant dev lists.]

This change is part of JEP 347; the intent is to target JDK 16.

Please review this change to the building of C++ code in the JDK to
enable the use of C++14 language features.  This change does not make
any code changes to use new features provided by C++11 or C++14.

This requires trimming the supported compiler versions, moving the
minimum supported versions forward (significantly, in some cases).
The new minimums are based on compiler documentation rather than
testing.  It may be that more recent versions are actually required.

This change needs to be tested on platforms not supported by Oracle.
The JEP test plan includes additional Oracle testing beyond what I’ve done.

CR:
https://bugs.openjdk.java.net/browse/JDK-8246032

Webrev:
https://cr.openjdk.java.net/~kbarrett/8246032/open.02/

Testing:
mach5 tier1-5 on Oracle supported platforms.

Performance testing showed no significant changes in either direction.

Build-only (no tests) for linux-arm32, linux-s390x, linux-ppc64le