[llvm] [llvm][Support] Add ARM64e support for split stacks (PR #139964)

[Ahmed Bougacha via llvm-commits]

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@@ -81,12 +84,20 @@ __asm__ (
     ".cfi_offset w29, -16\n\t"               // fp
 
     "mov       x0, x2\n\t"                   // Ctx is the only argument
+#if __arm64e__
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ahmedbougacha wrote:

And here:
```__has_feature(ptrauth_calls)```

https://github.com/llvm/llvm-project/pull/139964