[CUDA] Improve handling of math functions.
Summary:
A bunch of related changes here to our CUDA math headers.
- The second arg to nexttoward is a double (well, technically, long
double, but we don't have that), not a float.
- Add a forward-declare of llround(float), which is defined in the CUDA
headers. We need this for the same reason we need most of the other
forward-declares: To prevent a constexpr function in our standard
library from becoming host+device.
- Add nexttowardf implementation.
- Pull "foobarf" functions defined by the CUDA headers in the global
namespace into namespace std. This lets you do e.g. std::sinf.
- Add overloads for math functions accepting integer types. This lets
you do e.g. std::sin(0) without having an ambiguity between the
overload that takes a float and the one that takes a double.
With these changes, we pass testcases derived from libc++ for cmath and
math.h. We can check these testcases in to the test-suite once support
for CUDA lands there.
Reviewers: tra
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D23627
llvm-svn: 279140