[Libre-soc-bugs] [Bug 230] Video opcode development and discussion

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=230

--- Comment #39 from cand at gmx.com ---
Is the formulation in comment #27 not enough? To have it in BE, the mask needs
to be shifted to the other end, in addition to adjusting the shift.

The example from 3.0b page 266 has 128 bits of 7-bit data, and their vslv has
this weird byte-short focus. It's unlikely to find such a stream of data, but
to unpack that in our scheme I would pre-process it to vec4 units, so that one
32bit reg has 4*7=28 bits, suitably aligned.

There's basically two types of variable bit width data: pixel formats like
5-6-5 and compressed data ala Huffman. The former is rare, and the latter would
need sequential parsing to know their lengths, aka no point in vectorizing
that. So I don't think variable shift/mask amounts per-element are necessary
(but do point out if there's some use I missed).

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