MSL: Handle descriptor aliasing of raw buffer descriptors.

It is allowed to redeclare descriptors with different types in Vulkan.
MSL in general does not allow this, but for raw buffers, we can cast the
reference type at the very least.

For typed resources we are kinda hosed. Without descriptor indexing's
PARTIALLY_BOUND_BIT, descriptors must be valid if they are statically
accessed, so it would not be valid to access differently typed aliases
unless that flag is used. There might be a way to reinterpret cast
descriptors, but that seems very sketchy.

Implements support for:

- Single discrete descriptor
- Single argument buffer descriptor
- Array of argument buffer descriptors

Other cases are unimplemented for now since they are extremely painful
to unroll.

1 files changed, 3 insertions, 1 deletions

diff --git a/spirv_msl.hpp b/spirv_msl.hpp
index 0e5c76db..1a7ee5c0 100644
--- a/spirv_msl.hpp
+++ b/spirv_msl.hpp
@@ -1107,7 +1107,9 @@ protected:
 	const MSLConstexprSampler *find_constexpr_sampler(uint32_t id) const;
 
 	std::unordered_set<uint32_t> buffers_requiring_array_length;
-	SmallVector<uint32_t> buffer_arrays;
+	SmallVector<uint32_t> buffer_arrays_discrete;
+	SmallVector<std::pair<uint32_t, uint32_t>> buffer_aliases_argument;
+	SmallVector<uint32_t> buffer_aliases_discrete;
 	std::unordered_set<uint32_t> atomic_image_vars; // Emulate texture2D atomic operations
 	std::unordered_set<uint32_t> pull_model_inputs;