[llvm] Add a test to check return types for __size_returning_new LibFuncs. (PR #102391)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

This isn't what I meant. You need to add custom checking code to make sure that only `declare {ptr, i64} @__size_returning_new(i64)` gets recognized as the TLI function, but not for example `declare {i32, float} @__size_returning_new(i64)`. Unless I missed something, you will currently accept both.

https://github.com/llvm/llvm-project/pull/102391