[SimplifyLibCalls] Only consider sinpi/cospi functions within the same function

The sinpi/cospi can be replaced with sincospi to remove unnecessary
computations.  However, we need to make sure that the calls are within
the same function!

This fixes PR26993.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263875 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed