Previously we'd always lower @llvm.{sin,cos}.f32 to {sin.cos}.approx.f32
instruction even when unsafe FP math was not allowed.
Clang-generated IR is not affected by this as it uses precise sin/cos
from CUDA's libdevice when unsafe math is disabled.
Differential Revision: https://reviews.llvm.org/D28619
llvm-svn: 291936