MSL: Ensure discrete runtime arrays of buffers have known length.

An entry-point array of buffers, that is not part of a Metal argument
buffer, requires a known length, so it can be emitted as discrete buffers.
For runtime arrays of resources, this can be retrieved from the resource
binding information added via add_msl_resource_binding().

- Redefine get_resource_array_size() to consolidate array sizing using both var
  type, and runtime array sizing from resource bindings, if not found in type.
- Use get_resource_array_size() to fix issue for runtime arrays of buffers.
- Update runtime arrays of images and samplers to use get_resource_array_size().
- Add .DS_Store to .gitignore (unrelated).

.gitignore

@@ -21,5 +21,8 @@
 .vs/
 *.vcxproj.user
 
+# Mac OS X Finder
+.DS_Store
+
 !CMakeLists.txt
 !LICENSES/*.txt

spirv_msl.cpp

@@ -191,13 +191,19 @@ bool CompilerMSL::is_msl_resource_binding_used(ExecutionModel model, uint32_t de
 
 bool CompilerMSL::is_var_runtime_size_array(const SPIRVariable &var) const
 {
-	return is_runtime_size_array(get_variable_data_type(var)) && get_resource_array_size(var.self) == 0;
+	auto& type = get_variable_data_type(var);
+	return is_runtime_size_array(type) && get_resource_array_size(type, var.self) == 0;
 }
 
-// Returns the size of the array of resources used by the variable with the specified id.
+// Returns the size of the array of resources used by the variable with the specified type and id.
-// The returned value is retrieved from the resource binding added using add_msl_resource_binding().
+// The size is first retrieved from the type, but in the case of runtime array sizing,
-uint32_t CompilerMSL::get_resource_array_size(uint32_t id) const
+// the size is retrieved from the resource binding added using add_msl_resource_binding().
+uint32_t CompilerMSL::get_resource_array_size(const SPIRType &type, uint32_t id) const
 {
+	uint32_t array_size = to_array_size_literal(type);
+	if (array_size) 
+		return array_size;
+
 	StageSetBinding tuple = { get_entry_point().model, get_decoration(id, DecorationDescriptorSet),
 		                      get_decoration(id, DecorationBinding) };
 	auto itr = resource_bindings.find(tuple);
@@ -1399,7 +1405,8 @@ void CompilerMSL::emit_entry_point_declarations()
 			statement(get_argument_address_space(var), " ", type_to_glsl(buffer_type), "* ",
 			          to_restrict(var.self, true), name, "[] =");
 			begin_scope();
-			for (uint32_t i = 0; i < to_array_size_literal(type); ++i)
+			uint32_t array_size = get_resource_array_size(type, var.self);
+			for (uint32_t i = 0; i < array_size; ++i)
 				statement(name, "_", i, ",");
 			end_scope_decl();
 			statement_no_indent("");
@@ -13410,11 +13417,6 @@ void CompilerMSL::entry_point_args_discrete_descriptors(string &ep_args)
 				if (type.array.size() > 1)
 					SPIRV_CROSS_THROW("Arrays of arrays of buffers are not supported.");
 
-				// Metal doesn't directly support this, so we must expand the
-				// array. We'll declare a local array to hold these elements
-				// later.
-				uint32_t array_size = to_array_size_literal(type);
-
 				is_using_builtin_array = true;
 				if (is_var_runtime_size_array(var))
 				{
@@ -13442,6 +13444,7 @@ void CompilerMSL::entry_point_args_discrete_descriptors(string &ep_args)
 				}
 				else
 				{
+					uint32_t array_size = get_resource_array_size(type, var_id);
 					for (uint32_t i = 0; i < array_size; ++i)
 					{
 						if (!ep_args.empty())
@@ -15342,10 +15345,7 @@ std::string CompilerMSL::sampler_type(const SPIRType &type, uint32_t id)
 
 		// Arrays of samplers in MSL must be declared with a special array<T, N> syntax ala C++11 std::array.
 		// If we have a runtime array, it could be a variable-count descriptor set binding.
-		uint32_t array_size = to_array_size_literal(type);
+		uint32_t array_size = get_resource_array_size(type, id);
-		if (array_size == 0)
-			array_size = get_resource_array_size(id);
-
 		if (array_size == 0)
 		{
 			add_spv_func_and_recompile(SPVFuncImplVariableDescriptor);
@@ -15395,10 +15395,7 @@ string CompilerMSL::image_type_glsl(const SPIRType &type, uint32_t id)
 
 		// Arrays of images in MSL must be declared with a special array<T, N> syntax ala C++11 std::array.
 		// If we have a runtime array, it could be a variable-count descriptor set binding.
-		uint32_t array_size = to_array_size_literal(type);
+		uint32_t array_size = get_resource_array_size(type, id);
-		if (array_size == 0)
-			array_size = get_resource_array_size(id);
-
 		if (array_size == 0)
 		{
 			add_spv_func_and_recompile(SPVFuncImplVariableDescriptor);

spirv_msl.hpp

@@ -977,7 +977,7 @@ protected:
 	void emit_interface_block(uint32_t ib_var_id);
 	bool maybe_emit_array_assignment(uint32_t id_lhs, uint32_t id_rhs);
 	bool is_var_runtime_size_array(const SPIRVariable &var) const;
-	uint32_t get_resource_array_size(uint32_t id) const;
+	uint32_t get_resource_array_size(const SPIRType &type, uint32_t id) const;
 
 	void fix_up_shader_inputs_outputs();