TryDetile's exact-XOR fast path (PS5 swizzle modes 5/9/24/27) ran the
full AddrLib address equation per element: a 16-bit interleave with 32
PopCount calls for every pixel of textures that are millions of elements.
Each output bit is parity(x & XMask) XOR parity(y & YMask), and parity
distributes over XOR, so the offset factors into independent xTerm(x) ^
yTerm(y) fields. Precompute the per-column X term once and hoist the Y
term per row, collapsing the inner loop to one array load and one XOR.
Add GnmTilingDetileTests, which lays out a tiled buffer from an
independent re-derivation of the mode-27 equation and asserts TryDetile
reconstructs it byte-for-byte.
Co-authored-by: slick-daddy <slick-daddy@users.noreply.github.com>
1f3963c543