[llvm] [TLI] Add support for lgamma libcall. (PR #114536)

[Kenji Mouri / 毛利 研二 via llvm-commits]

MouriNaruto wrote:

> > Constant folding support will be submitted in a subsequent patch.
> 
> In my experience, constant folding the gamma function is not easy because it requires invoking the corresponding libc function, which is implemented differently on various platforms. I have noticed different return values on Windows and Linux (x86), two of the most commonly used platforms. Writing a test case to satisfy the LLVM build bot may not be that trivial. Good luck!

Thanks. I will try to implement this constant fold from the current LLVM codebase. I think I will learn a lot if I can make a proper PR for that.

Kenji Mouri

https://github.com/llvm/llvm-project/pull/114536