[libre-riscv-dev] sv 1d/2d/3d data shaping

[Luke Kenneth Casson Leighton]

On Mon, Oct 15, 2018 at 7:53 PM Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
>
> ok so i thought about this a bit more, and i believe it may be
> achievable with an additional (small!) CAM CSR table that contains the
> dimensions required and the order in which they are to be applied.  i
> am reluctant to specify all the permutations required of 3D at this
> stage however it may be ok to leave room for further expansion.
>
> the key thing here is to be able to "reorder" linear data with an
> algorithm that, for 2D, would go something like this:
>
> xdim = CSRtb[reg].x_sz
> ydim = CSRtb[reg].y_sz
>
> for idx in range(VL):
>   if (swap_xy)
>   {
>      new_idx = (idx % xdim) * ydim + (idx / ydim)
>   }

>>> for idx in range(12):
...     print (idx % 3) * 4 + (idx / 3)
...
0
4
8
1
5
9
2
6
10
3
7
11

it needs to be divide by xdim in each case (not idx / ydim).

that would make it possible to remap matrices of 3x4 into 4x3, but
leaving the data *in-place*.

my only concern is the addition of hardware logic which does the
divide and multiply, however i think an alternative algorithm based on
incrementing a pair of counters (for x in range(xdim): for y in
range(ydim)) at the same time as the element idx is incrementing might
do the trick.

l.