RFR: 8344355: Register corruption in MacroAssembler::lookup_secondary_supers_table_var: x86-64 only [v2]

[Vladimir Ivanov]

On Wed, 27 Nov 2024 01:02:47 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Ok, thanks for the pointer. 
>> 
>> I'm fine with keeping the patch as it is, but I would definitely prefer a cleaner way to zap registers when it comes to scaling its usage across the code base.
>> 
>> FTR there's a special  place `globalDefinitions.hpp` for constants used for debugging. And I'd be confused to find out that the constant is spelled in camel case after trying to grep for it :-)
>
> It might be useful to have a testing flag that simulates old hardware on modern hardware.  So for example, it would turn off UsePopCountInstruction.  We have something similar on x86 with UseKNLSetting.

Doesn't `-XX:UseSSE=2` achieve exactly that on x86-64?

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PR Review Comment: https://git.openjdk.org/jdk/pull/22365#discussion_r1859763278