RFR: 8323242: Remove vestigial DONT_USE_REGISTER_DEFINES

[Kim Barrett]

On Tue, 26 Mar 2024 04:55:55 GMT, Koichi Sakata <ksakata at openjdk.org> wrote:

>> This pull request removes an unnecessary directive.
>> 
>> There is no definition of DONT_USE_REGISTER_DEFINES in HotSpot or the build system, so this `#ifndef`conditional directive is always true. We can remove it. 
>> 
>> I built OpenJDK with Zero VM as a test. It was successful.
>> 
>> 
>> $ ./configure --with-jvm-variants=zero --enable-debug
>> $ make images 
>> $ ./build/macosx-aarch64-zero-fastdebug/jdk/bin/java -version                                                                                                                                         
>> openjdk version "23-internal" 2024-09-17                                                                                                                                                                                                                                                 
>> OpenJDK Runtime Environment (fastdebug build 23-internal-adhoc.jyukutyo.jyukutyo-jdk)                                                                                                                                                                                                    
>> OpenJDK 64-Bit Zero VM (fastdebug build 23-internal-adhoc.jyukutyo.jyukutyo-jdk, interpreted mode)
>> 
>> 
>> It may be possible to remove the `#define noreg` as well because the CONSTANT_REGISTER_DECLARATION macro creates a variable named noreg, but I can't be sure. When I tried removing the noreg definition and building the OpenJDK, the build was successful.
>
> PING: Could someone please review this pull request?
> I'd like to only focus on removing the `#ifndef` conditional directive in this PR, since considering whether to remove the `#define noreg` definition is outside of the scope of the JBS issue.

@jyukutyo This seems to have fallen through the cracks.  It's reviewed and waiting for you to request integration.

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PR Comment: https://git.openjdk.org/jdk/pull/18115#issuecomment-2187313890