[llvm] [clang] [lld] [FuncAttrs] Deduce `noundef` attributes for return values (PR #76553)

[Vitaly Buka via cfe-commits]

vitalybuka wrote:

Another problem is that there was assumption that definition and declaration will be consistent, for msan is a part of ABI.
Clang will generate them consistently for all modules, with declaration and definition of the function.

Is possible that after this patch some definitions will get noundef, but declarations in other modules will still have none? If that is so, it breaks msan.

https://github.com/llvm/llvm-project/pull/76553