RFR: 8364141: Remove LockingMode related code from x86

[Fredrik Bredberg]

On Wed, 30 Jul 2025 16:22:14 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Since the integration of [JDK-8359437](https://bugs.openjdk.org/browse/JDK-8359437) the `LockingMode` flag can no longer be set by the user, instead it's declared as `const int LockingMode = LM_LIGHTWEIGHT;`. This means that we can now safely remove all `LockingMode` related code from all platforms.
>> 
>> This PR removes `LockingMode` related code from the **x86** platform.
>> 
>> When all the `LockingMode` code has been removed from all platforms, we can go on and remove it from shared (non-platform specific) files as well. And finally remove the `LockingMode` variable itself.
>> 
>> Passes tier1-tier5 with no added problems.
>
> src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 389:
> 
>> 387: // obj: object to lock
>> 388: // rax: tmp -- KILLED
>> 389: // t  : tmp - cannot be obj nor rax -- KILLED
> 
> This same comment is repeated just above so you probably don't need it here.

Since it's more than 150 lives above, I'd rather keep this "copy" here.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26552#discussion_r2247860770