[Libre-soc-dev] Inverse DCT
Luke Kenneth Casson Leighton
lkcl at lkcl.net
Sun Aug 1 01:45:04 BST 2021
On 7/30/21, Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:
> next step, putting in a yield-based inverse DCT, was successful.
> next step is to link it into instructions and write a simulator unit test
the problem comes with the LD instruction.
FFT: bitreverse with shift
DCT: recursive halfswap then bitreverse
iDCT: bitreverse then inverse recursive halfswap
this is just too much to fit into SVP64 24 bit prefix, and the
LD-byterev is actually interfering with applying REMAP.
what i am thinking of doing is removing bytereversing ftom the
augmented LD and just having LD-with-shift, to which 3 REMAP modes
above can be applied.
this makes FFT about 13 instructions rather than 11 but pffh.
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