RFR: 8291555: Implement alternative fast-locking scheme [v71]

[Roman Kennke]

On Thu, 4 May 2023 20:49:22 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 666:
>> 
>>> 664:   // Invariant: tmpReg == 0.  tmpReg is EAX which is the implicit cmpxchg comparand.
>>> 665:   lock();
>>> 666:   cmpxchgptr(scrReg, Address(boxReg, OM_OFFSET_NO_MONITOR_VALUE_TAG(owner)));
>> 
>> Sigh... I had liked the fact that we took care of these old "TODO" items
>> in this code. It's true that these changes were in violation of our "try not
>> to change stack-lock" mantra. I did run the v66 changes thru Mach5
>> Tier[1-8] testing in "stack-locking is default" mode so your changes
>> were well tested.
>
> Let's re-do those changes in a follow-up, ok?

I've filed: https://bugs.openjdk.org/browse/JDK-8307493

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

PR Review Comment: https://git.openjdk.org/jdk/pull/10907#discussion_r1185503403