Otherwise ubsan reports runtime errors such as:
libs/vkd3d-shader/ir.c:4731:5: runtime error: null pointer passed as argument 1, which is declared to never be null
Creating a pool of 16k descriptors is wasteful if an allocator only uses
a fraction of them, so start at 1k and double for each subsequent
allocation until 16k is reached.
Now that our Vulkan descriptor sets contain only a single vkd3d
descriptor type, we're able to create descriptor pools containing only a
single vkd3d descriptor type as well. This avoids wasting unallocated
descriptors of one type when we run out of descriptors of another type.
We currently create statically sized descriptor pools, shared among
different descriptor types. Once we're unable to allocate a descriptor
set from a pool, we create a new pool. The unfortunate but predictable
consequence is that when we run out of descriptors of one type, we waste
any unallocated descriptors of the other types.
Dynamically adjusting the pool sizes could mitigate the issue, but it
seems non-trivial to handle all the edge cases, particularly in
situations where the descriptor count ratios change significantly
between frames. Instead, by storing only a single vkd3d descriptor type
in each Vulkan descriptor set we're able to create separate descriptor
pools for each vkd3d descriptor type, which also avoids the issue.
The main drawback of using separate descriptor sets for each descriptor
type is that we can no longer pack all bounded descriptor ranges into a
single descriptor set, potentially leaving fewer descriptor sets
available for unbounded ranges. That seems worth it, but we may end up
having to switch to a more complicated strategy if this ends up being a
problem on Vulkan implementations with a very limited number of
available descriptor sets.
Currently the mutable descriptor set is repeated many times in the
pipeline layout in order to cover the indices for all the
descriptor types that would be present if mutable descriptors were
not used. This is useless and wasteful, but was necessary before
the descriptor sets backing the SRV-UAV-CBV heap were moved at the
end of the allocation table because descriptor set indices are
currently a compile-time constant in many places.
Now this is not needed any more and we can just avoid putting
many copies of the mutable descriptor set in the pipeline layout,
making it easier to meet Vulkan implementation limits.
So we avoid hardcoding that it is number zero. There are two
goals here: first making the code easier to understand and
second allow reshuffling the descriptor set allocation in a
later commit.
Slightly simplifies descriptor write addressing, and makes layouts
essentially the same as array layouts, differing only in the binding
details, and therefore easier to understand. This also simplifies the
addition of storage buffer bindings, which can all be added onto the end.
Allows descriptor set layouts to be created after all bindings are
mapped. This is less complex and fragile than the current scheme, and in
a future patch it will support separating descriptor types into different
sets. Descriptors on virtual heaps are currently allocated from pools
which contain an equal number of each descriptor type used by vkd3d, and
this can waste a significant amount of device memory.
Enables the bounded range to be mapped to the unbounded one, instead of
being mapped to a separate binding which will be populated from the same
d3d12 descriptors as the unbounded one.
Based on the design document, "The runtime will not clamp or validate
the input, but implementations may clamp to the range [0,1] if necessary.",
so we test for the EXT_depth_range_unrestricted extension, and only clamp if
it's not available (thus, necessary to do so).
NaNs are converted to zero as per "NaNs must be treated as 0, but the runtime
will convert NaNs to 0 on behalf of the implementation.", and a default bounds
are set to 0.0 and 1.0.
The existing code sets "stageFlags" to VK_SHADER_STAGE_ALL when
"use_vk_heaps" is true, but doesn't adjust the visibility. This
potentially violates the "Any two elements of pPushConstantRanges must
not include the same stage in stageFlags" constraint, and causes the
validation layers to complain accordingly.
