A sampler with FORCE_DEGAMMA (S# word 0 bit 20) threw at decode, so
every dispatch or draw sampling through one was skipped.
DecodeSamplerResource now records the bit, but accepts it only for a
caller that pairs the sampler with its images. The direct sampler
binding does, and RequireDegammaFormat checks each sampled image
against its paired samplers: only already sRGB formats (8, 8_8 and
8_8_8_8 SRGB, BC1, BC2, BC3 and BC7 SRGB) pass, decoded once, as
shadPS4 (PS4) models it. Other textures and unpaired decodes still
throw; gfx10 behaviour is not measured.
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