[lworld] RFR: 8371993: [lworld] Aarch64: save bad values instead of rfp and lr above the extension space [v4]

[Marc Chevalier]

On Fri, 28 Nov 2025 08:32:47 GMT, Manuel Hässig <mhaessig at openjdk.org> wrote:

>> Marc Chevalier has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fewer macro
>
> That is a very useful continuation of this story arch.
> 
>> how should I name `save_fake_rfp_lr`?
> 
> `mangle_unused_rfp_lr`, `zap_unextended_rfp_lr` and permutations of those come to mind.
> 
>> is there an easier way to write a 64-bit immediate in a register in Aarch64?
> 
> You could load a constant from the constant pool (`ldr xTmp, =imm64`) if you want to trade off code size vs. having a load from memory. Otherwise, I think that your version is the best you can do.

I've changed a bit, to spare 2 macro invocations, as proposed by @mhaessig. Everybody happy?

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PR Comment: https://git.openjdk.org/valhalla/pull/1764#issuecomment-3589768157