[Libre-soc-bugs] [Bug 865] implement vector bitmanip opcodes

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=865

--- Comment #4 from Andrey Miroshnikov <andrey at technepisteme.xyz> ---
The nomenclature for pseudo-code is in the PowerISA spec, sections 1.3.2
onwards.

These are the instructions Luke gave at the end of the call yesterday:
pywriter 
add av.mdwn 
pywriter noall av

I added the changes to av.mdwn and minor_22.csv (don't have write permission to
openpower-isa, will push once given).

Now on to some question:

Does cprop stand for Carry Propagate? What does it actually do? Does it take
bits lower down, and shift them up?
I tried calculating the pseudo-code with two 4-bit numbers (RA:1011, RB:0110,
result: 1111) on paper, didn't understand the signifance of the result.

Also is cprop a bitmanip instruction?
If so, does it need to go into bitmanip.mdwn?

In the minor_22.csv, the entries are:
opcode,unit,internal op,in1,in2,in3,out,CR in,CR out,inv A,inv out,cry in,cry
ou

>From the pseudo-code alone I can't tell if carry in/out are being used. It
looks like there are only two inputs: RA, RB; one output RT. After looking at
other instructions, Rc seems to determine something (1-bit bitfield).

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