To make sure that apps actually get something when the HW doesn't
support ETC2. To do that we decompress after every copy operation.
Includes a quite complicated decode shader. It is not bit-to-bit
equivalent to AMD APUs that support ETC2, but close enough to
pass CTS. Likely missing bits are related to the R11 and R11G11
formats where we decode to 16 bits but likely do the extension
differently.
Acked-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14071>
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