RFR: 8243205: Modularize JVM flags declaration [v2]

[Stefan Karlsson]

On Tue, 8 Dec 2020 04:04:33 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.
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   stefank comments

Marked as reviewed by stefank (Reviewer).

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