RFR: 8241234: Unify monitor enter/exit runtime entries

[Yudi Zheng]

Hi Coleen,

Thanks for the review! Sorry I missed your email. And thanks Vladimir for the reminder.

>> I think you should have monitor_enter_helper and maybe monitor_exi_helper both take Handle as arguments.  This looks very strange.

Shall we change ObjectSynchronizer::exit to accept Handle as argument as well?

>> +void SharedRuntime::monitor_enter_helper(oopDesc* _obj, BasicLock* lock, JavaThread* thread) {
>> Because it creates a Handle anyway.  We try to eagerly pass Handle so that we don't have to search through the code to make sure there aren't any unhandled oops.
>> The _obj parameter name doesn't follow coding conventions (I was looking for it to be a field in something).

I took the parameter name from the original methods:
JRT_BLOCK_ENTRY(void, SharedRuntime::complete_monitor_locking_C(oopDesc* _obj, BasicLock* lock, JavaThread* thread))
JRT_LEAF(void, SharedRuntime::complete_monitor_unlocking_C(oopDesc* _obj, BasicLock* lock, JavaThread * THREAD))
Will Change that.

>> + oop obj(_obj);
>> Is there not already a implicit conversion from oopDesc* to oop?

Also took from the original methods. Will get rid of that.

Thanks,
Yudi

>> Thanks,
>> Coleen
>> On 3/20/20 11:03 AM, Yudi Zheng wrote:
>>> Hello,
>>> 
>>> Please review this patch that unifies the monitor enter/exit runtime entries used by C1, C2, and JVMCI.
>>> 
>>> https://bugs.openjdk.java.net/browse/JDK-8061553 added support for faster "slow" locking paths.
>>> These paths are not currently used by JVMCI (or C1) leading to slower performance on programs
>>> that have a lot of short lived locked sections (such as dacapo:h2).
>>> 
>>> This patch creates helper methods based on C2’s monitor enter/exit entries, and shares with the C1,
>>> JVMCI runtimes. It will prevent these runtimes from missing future updates.
>>> 
>>> https://bugs.openjdk.java.net/browse/JDK-8241234
>>> http://cr.openjdk.java.net/~yzheng/8241234/webrev.00/
>>> 
>>> Many thanks,
>>> Yudi