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

[bugzilla-daemon at libre-soc.org]

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

--- Comment #3 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
on the svp64 ldst imm mode
this line needs changing:

0-1     2       3 4     description
00      els     dz sz   normal mode

one option: when sz=dz=1, this enables bitreverse mode.  algorithm is:

# Returns the integer whose value is the reverse of the lowest 'width' bits of
the integer 'val'.
def reverse_bits(val, width):
        result = 0
        for _ in range(width):
                result = (result << 1) | (val & 1)
                val >>= 1
        return result

where width = log2(VL).

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