[llvm] Add metadata pointer regex substitution to MIR update script (PR #163253)

[via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 6
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saxlungs wrote:

Are you referring to the `# REQUIRES: amdgpu-registered-target` line in the test file? I'll be honest I don't really know what that line does, I was just following the lead of other tests in this and related directories. I agree, I don't think this behavior is necessarily limited to AMDGPU.

https://github.com/llvm/llvm-project/pull/163253