[llvm] [AArch64] Stop reserved registers from being saved in prolog/epilog (PR #138448)

[via llvm-commits]

yasuna-oribe wrote:

What a fail. I guess you can't just remove saved registers from the BitVector. I've drafted it for now, I'll come back to this later.
```
; CHECK-LABEL: _OUTLINED_FUNCTION_PROLOG_x30x29x19x20x22x23x24x25x26x27x28:
               ^
<stdin>:1:1: note: scanning from here
 .ios_version_min 7, 0
^
<stdin>:8:5: note: possible intended match here
 bl _OUTLINED_FUNCTION_PROLOG_x30x19x20x22x23x24x25x26x27x28
```


https://github.com/llvm/llvm-project/pull/138448