[Libre-soc-dev] bitmanip planning

[lkcl]

On November 4, 2021 10:28:57 PM UTC, Jacob Lifshay <programmerjake at gmail.com> wrote:
>On Thu, Nov 4, 2021, 15:17 lkcl <luke.leighton at gmail.com> wrote:
>
>>
>>
>> On November 4, 2021 9:55:44 PM UTC, Jacob Lifshay <
>> programmerjake at gmail.com> wrote:
>>
>> >Lkcl, where is the reference verilog?
>>
>> much of the complex ones that csme from RISCV xbitmanip went into
>picorv32
>> or into claire wolfe's repos.
>>
>> gaah this was a pain to find:
>>
>>
>>
>>
>https://github.com/cliffordwolf/xbitmanip/tree/71a19aad81369fbcf71b83e78564e0c8ee1b1b80/verilog
>
>
>Ah, thx!
>
>>
>>
>>
>> can i recommend starting with ridiculously small and obvious ones
>like
>> bitset / bitclear?
>
>
>Hmm, sounds good...I was planning on probably starting with the ternary
>op,
>the implementation should be pretty straightforward

yes, it is an extension of the implementation of crops from 2 bit to look up 4, to 3 bit to look up 8

>, though the
>instruction
>encoding might be more trouble. 

yes. it barely fits.

> If we're going to support 4-in 1-out
>ops,
>it might be worth having another ternary op where the lookup table is
>given
>by a register rather than an immediate field.

that's in there as well.  ternary and ternaryi.

>Jacob