[Libre-soc-bugs] [Bug 653] investigate FFT, DCT, etc for REMAP in SVP64

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Wed Jun 23 19:47:16 BST 2021


https://bugs.libre-soc.org/show_bug.cgi?id=653

--- Comment #5 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
argh, the decode for LDST is... not very clean.  for the +/- twin arithemtic
there is no change to the Forms, it is a matter of "if SVP64 Mode and OE=1
equals +/- twin arithmetic".

LD/ST is waay more involved, because the detection of whether SVP64 RM *itself*
is in LD/ST Mode involves first identifying if the *v3.0B suffix* is a LD/ST
operation.

once that is done, *then* bitreverse mode can be detected (in SVP64 RM)

once that is done, *then* the decoder can be flipped over to the new SVP64 LDST
instruction forms.

argh.

that's awful.

the only saving grace is that the detection only needs to be on MAJOR opcodes,
because only the major opcodes are big enough to fit LD/ST with immediate.

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