[lworld] RFR: 8371993: [lworld] Aarch64: save bad values instead of rfp and lr above the extension space

[Marc Chevalier]

On Fri, 28 Nov 2025 08:45:52 GMT, Marc Chevalier <mchevalier at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 5911:
>> 
>>> 5909:       movk(rscratch1, (badRegWordVal >> 16) & 0xffff, 16);
>>> 5910:       movk(rscratch1, badRegWordVal & 0xffff, 32);
>>> 5911:       movk(rscratch1, (badRegWordVal >> 16) & 0xffff, 48);
>> 
>> This should go in its own function in the macro assembler.
>
> I was trying to find such a function, because I assumed I wasn't the first one wanting to move a 64 immediate in a register in aarch64. I hoped to replace that by a call to an existing function. But if you're also not aware of anything, maybe I'm the first one! Any then, I agree. It shall be moved.

Nevermind, I found mov_immediate64. No idea how I missed that.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1764#discussion_r2570975134