[llvm] [NVPTX] Support llvm.{exp2, log2} for f32/f16/bf16 and vectors (PR #120519)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

> @jhuber6 you've dealt with the math library recently. Do you know what are the expectations for the precision of `exp2f`?

The expected precision isn't really documented in the general sense, but OpenCL has some guidelines, or you could look at what GCC currently offers. OpenCL states that `exp2` should be Within 3 ULP https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_C.html#relative-error-as-ulps. 

https://github.com/llvm/llvm-project/pull/120519