[clang] [llvm] [InstCombine] Combine llvm.sin/llvm.cos libcall pairs into llvm.sincos (PR #184760)

[Matt Arsenault via cfe-commits]

================

----------------
arsenm wrote:

Can you test the behavior with fpmath metadata? Ideally the combined call would use getMostGenericFPMath from the 2. Also test flag preservation, which should intersect 

https://github.com/llvm/llvm-project/pull/184760