[llvm] [Windows] Allow legalizing LDEXP_F128 and FREXP_F128 with libcalls (PR #148326)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

SelectionDAGLegalize::expandLdexp has code to expand ldexp inline; do we want to do that?  I can see why we might not want to, I guess, since it's a lot of code to generate inline.

I'd prefer to get the libcall names correct before we merge this: ldexpl exists on Windows, and it's the wrong function, so you're turning a crash into a miscompile.

https://github.com/llvm/llvm-project/pull/148326