what's the meaning for CPKAB and CPKCD operation?

[bysg]

In the README.md, CPKAB and CPKCD operation is introduced, but I cannot get the meaning of these operations, or is there some difference between CPKAB and CPKCD? or op_mod is 0 or 1?

I read the rtl code(fpnew_opgroup_multifmt_slice.sv and fpnew_cast_multi.sv), and I tried to run some simulations to help understand,
however, when

1. src_fmt is fp64, dst_fmt is fp16, op=fpnew_pkg::CPKAB, op=0
2. src_fmt is fp64, dst_fmt is fp16, op=fpnew_pkg::CPKAB, op=1
3. src_fmt is fp64, dst_fmt is fp16, op=fpnew_pkg::CPKCD, op=0
4. src_fmt is fp64, dst_fmt is fp16, op=fpnew_pkg::CPKCD, op=1
   I got the same result.

So is there some detail description for CPKAB and CPKCD operation?
thanks.

[GiannaP]

It is converting e.g. fp64 (D) into fp8 (B) and puts them into the correct position for SIMD packed fp data in a 64bit datapath. CPKAB takes care of the lower positions and CPKCD of the higher positions.

Indeed we recently fixed some issues for our latest project. One issue was related to the CPKCD operations. Have a look at the commits on this separate branch:

https://github.com/openhwgroup/cvfpu/commits/bugfix/vfcpk