[llvm] [AArch64] Fix assertion failure during promotion of EXTEND_VECTOR_INREG. (PR #171619)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,14 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=aarch64-unknown-linux-musl < %s | FileCheck %s
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arsenm wrote:

```suggestion
; RUN: llc -mtriple=aarch64-unknown-linux < %s | FileCheck %s
```

Environment not relevant to the test 

https://github.com/llvm/llvm-project/pull/171619