[master] RFR: 8300527: [Lilliput] Simplify and optimize loading of Klass*

[Aleksey Shipilev]

On Mon, 23 Jan 2023 13:34:50 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> With the new fast-locking, we can greatly simplify the loading of the Klass* from an object. We no longer have to call into the runtime to ensure that the header is changed under our feet (by installing the INFLATION marker). Instead, we can do a simple check for the object being monitor-locked, and safely load the displaced header, if that is the case.

Minor nits.

src/hotspot/share/c1/c1_LIR.cpp line 891:

> 889:       do_input(opLoadKlass->_obj);
> 890:       do_output(opLoadKlass->_result);
> 891:       do_stub(opLoadKlass->stub());

Minor: why not leave `_stub`?

src/hotspot/share/runtime/synchronizer.cpp line 798:

> 796: static SharedGlobals GVars;
> 797: 
> 798: static markWord read_stable_mark(oop obj) {

Do you still need this method, or? If you still need it, let's not put it outside the `ObjectSynchronizer` "namespace".

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Marked as reviewed by shade (Committer).

PR: https://git.openjdk.org/lilliput/pull/66