[mlir][spirv] Define spv.IsNan/spv.IsInf and add lowerings

Authored by antiagainst on Jan 22 2021, 10:08 AM.


[mlir][spirv] Define spv.IsNan/spv.IsInf and add lowerings

spv.Ordered/spv.Unordered are meant for OpenCL Kernel capability.
For Vulkan Shader capability, we should use spv.IsNan to check
whether a number is NaN.

Add a new pattern for converting std.cmpf ord|uno to spv.IsNan
and bumped the pattern converting to spv.Ordered/spv.Unordered
to a higher benefit. The SPIR-V target environment will properly
select between these two patterns.

Reviewed By: mravishankar

Differential Revision: https://reviews.llvm.org/D95237