[llvm] AArch64: support extended spills in SEH on WoS (PR #166849)

[Saleem Abdulrasool via llvm-commits]

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+; RUN: llc -mtriple aarch64-unknown-windows-msvc -filetype asm -o - %s | FileCheck %s
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compnerd wrote:

I can certainly update the test to use `update_llc_test_checks.py` but that feels like it is less clear _what_ it is testing. The current incantation explicitly shows that we are looking at the spills and associated SEH opcodes.

https://github.com/llvm/llvm-project/pull/166849