RFR: 8243205: Modularize JVM flags declaration

[Coleen Phillimore]

On Thu, 3 Dec 2020 21:51:42 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> This is the first step for modularizing the xxx_globals.hpp. The goals are
> 
> - Improve modularization of HotSpot source
> - Reduce JVM build time
> 
> To prove that this works,  I have moved compiler_globals.hpp outside of the monolithic globals.hpp. Before this fix, compiler_globals.hpp was included by 922 HotSpot .o files. After this fix, it's included by 283 .o files.
> 
> I plan to do more refactoring later, such as:
> 
> - move gc_globals.hpp out of globals.hpp
> - move the flags related to tiered compilation (about 40 flags) out of globals.hpp
> - move the platform-specific flags outside of globals.hpp
>   - these flags should be used only by platform-specific files. They shouldn't be used by shared files.
> 
> Note: this is target for JDK 17.
> 
> Testing: I've tested tier1, builds-tier2, builds-tier3, builds-tier4 and builds-tier5 on mach5, plus locally building arm, aarch64, s390, ppc64, and zero.

Ok, this makes sense.

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Marked as reviewed by coleenp (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1608