[Libre-soc-dev] [RFC] REMAP, SHAPE, complex (full) FFT

Luke Kenneth Casson Leighton lkcl at lkcl.net
Tue Jul 20 16:01:16 BST 2021

On Tue, Jul 20, 2021 at 12:56 PM Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> ---
> crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
> On Tue, Jul 20, 2021 at 11:27 AM Luke Kenneth Casson Leighton
> <lkcl at lkcl.net> wrote:
> > Henriok, if you are happy to look at how the need for swap
> > instructions can be removed that would be fantastic.
> see attached patch: i suspect it's going to be something like this

it was - sorry Henriok, i had to tackle it: the DCT using Vertical-First
mode would have been far too complex, with having to pause one
type of Schedule and push it onto a stack.

the solution was indeed to do *double* levels of redirection of
the data:


currently i have a reordering phase in the middle of the butterflies,
however i *believe* it will be possible to *pre-load* the data in just the
right inversed-order, and also set the "swapping" indices up in an

such that on completion of the inner butterfly *the data arrives at
the correct positions*.


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