[llvm] SimplifyLibCalls: Don't require ldexp to emit intrinsic in exp2 combine (PR #92707)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> and on X86 that gets lowered to a call to ldexp() (which may or may not be the library call).

Assuming the runtime libcalls are set up accuratly, this should hit the inline expansion we get today and nothing will break. We do not just unconditionally lower the intrinsic to the libcall, although the control-flow free expansion might not be what you want 

https://github.com/llvm/llvm-project/pull/92707