RFR: 8319799: Recursive lightweight locking: x86 implementation [v12]

[Roman Kennke]

On Thu, 25 Jan 2024 08:32:05 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> I'll fix that. Went down a rabbit hole trying to figure out adlc and register allocation. I do not know why they specify `rbx` for `box`. Is it because they want to use `USE_KILL` or are they using `USE_KILL` because they specify `rbx` for `box`. It feels like this specification could be improved. The only requirement is that one tmp register is `rax`. But I will leave that to another RFE.

I don't know this, either. This might well be historical. I seem to remember that a much earlier version of that code shared code with interpreter version and used fixed registers there, but I am not sure. If it's not needed for the new code then don't do it. I don't think it has anything to do with USE_KILL, though. USE_KILL only means that it's using the input value of the register *and* overwrites (kills) it.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16607#discussion_r1466224835