PPSA21564's galaxy map renders a 1920x1080 surface as a color target whose
CB names DCC keys at one address and then writes it from a compute shader
whose T# names keys at another. Both key ranges read uncompressed every
frame, but the storage cache remade the surface's image whenever a
descriptor named metadata other than the image's, so the image was
flushed, destroyed, created and uploaded twice a frame (1231 constructions
in a 56 s scene), with the views and draw recipes built on it thrown away
each time.
A descriptor naming other keys now keeps the image when the move is
unobservable: the image's own keys and the named keys both read
uncompressed, and its content was neither uploaded nor filled under a
clear code. That is exactly the content an image made under the named
keys would hold once this one's pending results were stored. Any other
case (a fast clear of either key range, a register clear, an image
holding a clear) still remakes the image as before, so clears of the new
keys reach it and pending results are stored first.
Every proof that stands in for a lookup checks the same rule: the sampled
view hit, the fast revalidation of views and storage elements (storage
elements now record their descriptor's keys), the own-object refresh, and
the draw recipe's resident targets. Named-key scans keep per-image proofs,
so a repeated check costs no scan while the key bytes are unstamped.
agc_dcc_key_sharing drives KeysServeSurface, the rule ServesKeysAt uses,
through a model of the storage cache.
Dean Galvin