RFR: 8347830: [premain] UseCompatibleCompressedOops is broken after merging with mainline

[Ashutosh Mehra]

On Fri, 16 May 2025 14:58:08 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> src/hotspot/share/cds/cdsConfig.cpp line 140:
>> 
>>> 138:     FLAG_SET_ERGO_IF_DEFAULT(UseCompatibleCompressedOops, true);
>>> 139:   } else if (!FLAG_IS_DEFAULT(UseCompatibleCompressedOops)) {
>>> 140:     FLAG_SET_ERGO(UseCompatibleCompressedOops, false);
>> 
>> Why do we need to set it to false explicitly here? If it is not default shouldn't we use whatever value the user specified?
>
> I consider the flag make sense only for AOT code and not for general usage. See description: [globals.hpp#L132](https://github.com/openjdk/leyden/blob/premain/src/hotspot/share/runtime/globals.hpp#L132)
> 
> We don't want generate more complex encoding if we don't generate/use AOT code. Or compressed oops are off.
> We had also recently discussed how we should disable some AOT features if AOT caching is off - the conclusion was that we should silently ignore them (may be produce UL output on demand). That is why I used ERGO setting.

okay

-------------

PR Review Comment: https://git.openjdk.org/leyden/pull/67#discussion_r2093273404