swift234

Intrinsics instead of shims (#3530)

* Use intrinsics instead of Libc stubs where we can.

This replaces most of the stubs used for basic operations on these
types with intrinsics, eliminating a level of indirection for fma,
ceil, floor, round, trunc.

square root and remainder still require stubs because there is no
remainder intrinsic and we can't use the square root intrinsic because
its behavior is undefined for negative inputs.  A previous commit
apparently either the compiler annotates static inline stubs wrong
or the SIL verifier can't handle them, so that change was backed out.

* Explicitly CHECK-NOT @llvm.sqrt instead of looking for @sqrt.