[llvm] Minimal unwinding information (DWARF CFI) checker (PR #145633)

[Simon Tatham via llvm-commits]

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@@ -10,28 +11,34 @@ _start:
         .cfi_same_value %rsi
 
         pushq   %rbp
+        # CHECK: warning: unknown change happened to register RBP unwinding rule structure
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statham-arm wrote:

I see that you weren't able to add a `FileCheck` that enforces a lack of warnings here. But instead you've written some `CHECK:` lines, without any `FileCheck` that _does_ look for them?

https://github.com/llvm/llvm-project/pull/145633