[llvm] [llvm-c] Create a 128 bit floating point constant from 2 64 bit values (PR #164381)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Needs tests.

I also think it would make more sense to make this a generic bitwise initializer for FP constants, rather than specific to fp128. That will also work for things like ppc_fp128, and generally to more reliably create specific FP values, even if they're special. (Like, I wouldn't expect the API taking a double to reliably create an sNaN with a specific payload.)

https://github.com/llvm/llvm-project/pull/164381