RFR: 8265518: C1: Intrinsic support for Preconditions.checkIndex [v13]

[Thomas Stuefe]

On Wed, 9 Jun 2021 08:53:40 GMT, Yi Yang <yyang at openjdk.org> wrote:

>> The JDK codebase re-created many variants of checkIndex(`grep -I -r 'cehckIndex' jdk/`). A notable variant is java.nio.Buffer.checkIndex, which annotated with @IntrinsicCandidate and it only has a corresponding C1 intrinsic version.
>> 
>> In fact, there is an utility method `jdk.internal.util.Preconditions.checkIndex`(wrapped by java.lang.Objects.checkIndex) that behaves the same as these variants of checkIndex, we can replace these re-created variants of checkIndex by Objects.checkIndex, it would significantly reduce duplicated code and enjoys performance improvement because Preconditions.checkIndex is @IntrinsicCandidate and it has a corresponding intrinsic method in HotSpot.
>> 
>> But, the problem is currently HotSpot only implements the C2 version of Preconditions.checkIndex. To reuse it global-widely in JDK code, I think we can firstly implement its C1 counterpart. There are also a few kinds of stuff we can do later:
>> 
>> 1. Replace all variants of checkIndex by Objects.checkIndex in the whole JDK codebase.
>> 2. Remove Buffer.checkIndex and obsolete/deprecate InlineNIOCheckIndex flag
>> 
>> Testing: cds, compiler and jdk
>
> Yi Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   more comment

Hi Yi,

you may need to add the option to the obsolete-flags-table though as described in arguments.cpp:

https://github.com/openjdk/jdk/blob/5cee23a9ed0b7fe2657be7492d9c1f78fcd02ebf/src/hotspot/share/runtime/arguments.cpp#L489-L490

I think the point is to give a customer a grace period where the option is still accepted on the command line. I am not sure if that step is optional though, if one is reasonably sure that the option is unused. Maybe @dholmes-ora can chime in.

Cheers, Thomas

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PR: https://git.openjdk.java.net/jdk/pull/3615