RFR: 8256675: Zero: purge biased locking support

[Coleen Phillimore]

On Thu, 19 Nov 2020 16:23:54 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Biased locking support was always disabled for C++ interpreter. Zero seems to have inherited that, see block in `arguments.cpp`:
> 
> #ifdef ZERO
>   // Clear flags not supported on zero.
>   FLAG_SET_DEFAULT(ProfileInterpreter, false);
>   FLAG_SET_DEFAULT(UseBiasedLocking, false);
>   LP64_ONLY(FLAG_SET_DEFAULT(UseCompressedOops, false));
>   LP64_ONLY(FLAG_SET_DEFAULT(UseCompressedClassPointers, false));
> #endif // ZERO
> 
> But `zero/bytecodeInterpreter.cpp` still has paths that imply biased locking support. Seeing that biased locking can go away, and the cost/benefit balance of supporting it in Zero, it makes more sense to purge the long-time-disabled biased locking support from Zero.
> 
> Additional testing:
>  - [x] Ad-hoc benchmark runs with `-XX:(-|+)UseBiasedLocking` (Zero is so slow that BL does not matter)

Wow that was a lot of code.  Looks good to me.

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Marked as reviewed by coleenp (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1322