[llvm] [ARM] Fix MRC cp10 and cp11 warning (PR #126407)

[Oliver Stannard via llvm-commits]

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@@ -173,6 +173,10 @@
         @ p10 and p11 are reserved for NEON
         mcr p10, #2, r5, c1, c1, #4
         mcrr p11, #8, r5, r4, c1
+        mrc p10, #7, r5, c1, c1, #0
+        mrc p11, #7, r5, c1, c1, #0
+@ CHECK-WARN: warning: since v7, cp10 and cp11 are reserved for advanced SIMD or floating point instructions
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ostannard wrote:

The problem is that no `RUN` lines at the top of the file do anything with `CHECK-WARN`, so it's just a comment and doesn't do anything. I think you can just change this to `CHECK-ERRORS`, assuming that the same message is emitted for both commands at the top of the file.

https://github.com/llvm/llvm-project/pull/126407