This change adds the following NVVM Ops for new narrow FP conversions
introduced in PTX 9.1:
- `convert.{f32x2/bf16x2}.to.s2f6x2`
- `convert.s2f6x2.to.bf16x2`
- `convert.bf16x2.to.f8x2` (extended for `f8E4M3FN` and `f8E5M2` types)
- `convert.{f16x2/bf16x2}.to.f6x2`
- `convert.{f16x2/bf16x2}.to.f4x2`
PTX ISA Reference:
https://docs.nvidia.com/cuda/parallel-thread-execution/#data-movement-and-conversion-instructions-cvt
Multi-Level Intermediate Representation
See https://mlir.llvm.org/ for more information.