[jira] Commented: (HARMONY-5464) [drlvm] vm helper improvement for better performance

["Pavel Pervov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HARMONY-5464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12566488#action_12566488 ] 

Pavel Pervov commented on HARMONY-5464:
---------------------------------------

Maksim,

I do not really understand the difference between throwing NPE from inside the helper and causing signal handler to throw NPE as a result of a call to invalid address. BTW, is it guaranteed that referenced address will be inaccessible to read by the VM?

Could you, please, clarify those for me?

Thanks.

> [drlvm] vm helper improvement for better performance
> ----------------------------------------------------
>
>                 Key: HARMONY-5464
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5464
>             Project: Harmony
>          Issue Type: Improvement
>          Components: DRLVM
>         Environment: Hope it works everywhere
>            Reporter: Maksim Ananjev
>            Assignee: Alexey Varlamov
>            Priority: Minor
>         Attachments: HARMONY_5464.patch
>
>
> The issue deals with "load interface vtable support".  Returning zero address and not generating NPE if the object is null is safe in terms of preserving program semantics(the exception will be generatedon the first method invocation) and allows profitable code transformations such as hoisting vm helper outside the loop body. This is our current convention which touches all variants of this helper. If it changes, all variants must be fixed
> The patch also includes osr_path enabling because it depends on this feature.

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