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

[Ahmed Bougacha via llvm-commits]

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@@ -70,6 +70,9 @@ __asm__ (
     ".p2align  2\n\t"
     "_ZN4llvm17runOnNewStackImplEPvPFvS0_ES0_:\n\t"
     ".cfi_startproc\n\t"
+#if __arm64e__
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ahmedbougacha wrote:

Perhaps:
```__has_feature(ptrauth_returns)```
here and around the retab

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