[clang] [llvm] [PowerPC][AIX] Support #pragma comment copyright for AIX (PR #178184)

[Wael Yehia via cfe-commits]

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w2yehia wrote:

Diagnostics tests should not be in Codegen.
Codegen tests should just test the expected LLVM IR for this feature.
I would split out the diagnostics portion into the test in the Preprocessor directory.

https://github.com/llvm/llvm-project/pull/178184