RFR: 8309543: Micro-optimize x86 assembler UseCondCardMark

[Martin Doerr]

On Tue, 6 Jun 2023 14:24:14 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Noticed this while explaining a related code: there is no need to make a full jump, and a short jump would suffice. Assembler does not know about this shortening, because it is a forward branch.
> 
> Makes a slightly more compact interpreter code.

Looks good.
I side note: I wonder if it makes any sense to use conditional card marking in the interpreter. I don't think it's fast enough to cause trouble in the processor's memory subsystem by executing oop accesses. Maybe shorter code, less complexity and fewer branches would be a better choice for the interpreter?

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PR Comment: https://git.openjdk.org/jdk/pull/14335#issuecomment-1578957992