[PartialInlineLibCalls] Teach PartialInlineLibCalls to honor nobuiltin, properly...

[PartialInlineLibCalls] Teach PartialInlineLibCalls to honor nobuiltin, properly check the function signature, and check TLI::has

Summary:
We shouldn't do this transformation if the function is marked nobuitlin.

We were only checking that the return type is floating point, we really should be checking the argument types and argument count as well. This can be accomplished by using the other version of getLibFunc that takes the Function and not just the name.

We should also be checking TLI::has since sqrtf is a macro on Windows.

Fixes PR32559.

Reviewers: hfinkel, spatel, davide, efriedma

Reviewed By: davide, efriedma

Subscribers: efriedma, llvm-commits, eraman

Differential Revision: https://reviews.llvm.org/D39381

llvm-svn: 316819