RFR: JDK-8323497: On x64, use 32-bit immediate moves for narrow klass base if possible

[Aleksey Shipilev]

On Wed, 10 Jan 2024 18:41:44 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>>> FYI the logic for immediate matching is:
>> 
>> @merykitty, could you point me where that logic is? Cannot find it in current Hotspot sources, and would like to reference it in my PR.
>
> @shipilev It is just the code representation of the matching, the corresponding nodes are `loadConUL32`, `loadConL32` and `loadConL` and the matcher uses node costs to sort out the priority.
> 
> https://github.com/openjdk/jdk/blob/c1282b57f50002edd08c93aed784390cca83b9b8/src/hotspot/cpu/x86/x86_64.ad#L4807

Oh, subtle. Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/17340#discussion_r1447788810