Lowering some vector comparision builtins to fcmp IR instructions.
This ignores the signaling behaviour specified in the predicate
argument of said builtins.
Affected AVX512 builtins:
builtin_ia32_cmpps128_mask
builtin_ia32_cmpps256_mask
builtin_ia32_cmpps512_mask
builtin_ia32_cmppd128_mask
builtin_ia32_cmppd256_mask
builtin_ia32_cmppd512_mask
Sink this into the switch as the default case with an llvm_unreachable