RFR: 8269122: The use of "extern const" for Register definitions generates poor code [v3]

[Andrew Haley]

On Tue, 22 Jun 2021 17:26:48 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Andrew Haley has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update copyright
>
> src/hotspot/share/asm/register.hpp line 50:
> 
>> 48: #define AS_REGISTER(type,name)         ((type)name##_##type##EnumValue)
>> 49: 
>> 50: #ifndef USE_EXTERN_CONST_FOR_REGISTER_DEFINITIONS
> 
> I can see this conditionalization being useful for development and testing of this change, but why keep it and the old, now dead, code?

The old code was a workaround for compilers that don't handle inline constants well. There are ports that I don't know about or can't test, and there are some outside the main jdk/jdk tree. If this change breaks any of them, all they have to do is define USE_EXTERN_CONST_FOR_REGISTER_DEFINITIONS. If it turns out that no such systems still exist, we can take it out.

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PR: https://git.openjdk.java.net/jdk/pull/4554