Tune memory layout so that we can deduce various information without
making a single pointer dereference:
- d3d12_descriptor_heap*
- heap offset
- Pointer to various side data structures we need to keep around.
Instead of having one big 64 byte data structure with tons of padding,
tune it down to 32 + 8 bytes per descriptor of extra dummy data.
To make all of this work, use a somewhat clever encoding scheme for CPU
VA where lower bits store number of active bits used to encode
descriptor offset. From there, we can mask away bits to recover
d3d12_descriptor_heap. Metadata is stored inline in one big allocation,
and we can just offset from there based on extracted log2i_ceil(descriptor count).
Signed-off-by: Hans-Kristian Arntzen <post@arntzen-software.no>
Hans-Kristian Arntzen
rochaudhari