Some conversions are not directly supported in hardware and need to be
split in two conversion instructions going through an intermediary type.
Doing this at the NIR level simplifies a bit the complexity in the backend.
v2:
- Consider fp16 rounding conversion opcodes
- Properly handle swizzles on conversion sources.
v3
- Run the pass earlier, right after nir_opt_algebraic_late (Jason)
- NIR alu output types already have the bit-size (Jason)
- Use 'is_conversion' to identify conversion operations (Jason)
v4:
- Be careful about the intermediate types we use so we don't lose
range and avoid incorrect rounding semantics (Jason)
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com> (v1)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
