MSL: Fix regression error in argument buffer runtime arrays.

Argument buffers can contain multiple runtime arrays if they have fixed
lengths as specified by the binding API. Regression error had assumed each
runtime array is in separate argument buffer with undefined array length.

- Add CompilerMSL::is_var_runtime_size_array() to include test for
  setting of array length via CompilerMSL::add_msl_resource_binding().

- Fixed unrelated test case MSL compile syntax failure when acceleration
  structure is the first entry point function argument (unrelated).

reference/shaders-msl-no-opt/frag/ray-query-mutability.spv14.vk.msl24.frag

@@ -61,7 +61,7 @@ uint proceeFn(thread raytracing::intersection_query<raytracing::instancing, rayt
     return _50;
 }
 
-fragment void main0(, raytracing::acceleration_structure<raytracing::instancing> topLevelAS [[buffer(0)]])
+fragment void main0(raytracing::acceleration_structure<raytracing::instancing> topLevelAS [[buffer(0)]])
 {
     raytracing::intersection_query<raytracing::instancing, raytracing::triangle_data> rayQuery;
     initFn(rayQuery, topLevelAS);

spirv_msl.cpp

@@ -189,6 +189,11 @@ bool CompilerMSL::is_msl_resource_binding_used(ExecutionModel model, uint32_t de
 	return itr != end(resource_bindings) && itr->second.second;
 }
 
+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;
+}
+
 // Returns the size of the array of resources used by the variable with the specified id.
 // The returned value is retrieved from the resource binding added using add_msl_resource_binding().
 uint32_t CompilerMSL::get_resource_array_size(uint32_t id) const
@@ -1361,7 +1366,7 @@ void CompilerMSL::emit_entry_point_declarations()
 		const auto &type = get_variable_data_type(var);
 		const auto &buffer_type = get_variable_element_type(var);
 		const string name = to_name(var.self);
-		if (is_runtime_size_array(type))
+		if (is_var_runtime_size_array(var))
 		{
 			if (msl_options.argument_buffers_tier < Options::ArgumentBuffersTier::Tier2)
 			{
@@ -10503,7 +10508,7 @@ void CompilerMSL::emit_function_prototype(SPIRFunction &func, const Bitset &)
 			// Manufacture automatic sampler arg for SampledImage texture
 			if (arg_type.image.dim != DimBuffer)
 			{
-				if (arg_type.array.empty() || is_runtime_size_array(arg_type))
+				if (arg_type.array.empty() || (var ? is_var_runtime_size_array(*var) : is_runtime_size_array(arg_type)))
 				{
 					decl += join(", ", sampler_type(arg_type, arg.id), " ", to_sampler_expression(name_id));
 				}
@@ -11693,8 +11698,7 @@ string CompilerMSL::to_buffer_size_expression(uint32_t id)
 		auto array_expr = expr.substr(index);
 		if (auto var = maybe_get_backing_variable(id))
 		{
-			auto &var_type = get<SPIRType>(var->basetype);
-			if (is_runtime_size_array(var_type))
+			if (is_var_runtime_size_array(*var))
 			{
 				if (!msl_options.runtime_array_rich_descriptor)
 					SPIRV_CROSS_THROW("OpArrayLength requires rich descriptor format");
@@ -13227,7 +13231,7 @@ void CompilerMSL::entry_point_args_discrete_descriptors(string &ep_args)
 				uint32_t array_size = to_array_size_literal(type);
 
 				is_using_builtin_array = true;
-				if (is_runtime_size_array(type))
+				if (is_var_runtime_size_array(var))
 				{
 					add_spv_func_and_recompile(SPVFuncImplVariableDescriptorArray);
 					if (!ep_args.empty())
@@ -13289,7 +13293,7 @@ void CompilerMSL::entry_point_args_discrete_descriptors(string &ep_args)
 			if (!ep_args.empty())
 				ep_args += ", ";
 			ep_args += sampler_type(type, var_id) + " " + r.name;
-			if (is_runtime_size_array(type))
+			if (is_var_runtime_size_array(var))
 				ep_args += "_ [[buffer(" + convert_to_string(r.index) + ")]]";
 			else
 				ep_args += " [[sampler(" + convert_to_string(r.index) + ")]]";
@@ -13307,7 +13311,7 @@ void CompilerMSL::entry_point_args_discrete_descriptors(string &ep_args)
 				if (r.plane > 0)
 					ep_args += join(plane_name_suffix, r.plane);
 
-				if (is_runtime_size_array(type))
+				if (is_var_runtime_size_array(var))
 					ep_args += "_ [[buffer(" + convert_to_string(r.index) + ")";
 				else
 					ep_args += " [[texture(" + convert_to_string(r.index) + ")";
@@ -13338,17 +13342,21 @@ void CompilerMSL::entry_point_args_discrete_descriptors(string &ep_args)
 		}
 		case SPIRType::AccelerationStructure:
 		{
-			if (is_runtime_size_array(type))
+			if (is_var_runtime_size_array(var))
 			{
 				add_spv_func_and_recompile(SPVFuncImplVariableDescriptor);
 				const auto &parent_type = get<SPIRType>(type.parent_type);
-				ep_args += ", const device spvDescriptor<" + type_to_glsl(parent_type) + ">* " +
+				if (!ep_args.empty())
+					ep_args += ", ";
+				ep_args += "const device spvDescriptor<" + type_to_glsl(parent_type) + ">* " +
 				           to_restrict(var_id, true) + r.name + "_";
 				ep_args += " [[buffer(" + convert_to_string(r.index) + ")]]";
 			}
 			else
 			{
-				ep_args += ", " + type_to_glsl(type, var_id) + " " + r.name;
+				if (!ep_args.empty())
+					ep_args += ", ";
+				ep_args += type_to_glsl(type, var_id) + " " + r.name;
 				ep_args += " [[buffer(" + convert_to_string(r.index) + ")]]";
 			}
 			break;
@@ -13440,7 +13448,7 @@ void CompilerMSL::fix_up_shader_inputs_outputs()
 				entry_func.fixup_hooks_in.push_back(
 				    [this, &type, &var, var_id]()
 				    {
-					    bool is_array_type = !type.array.empty() && !is_runtime_size_array(type);
+					    bool is_array_type = !type.array.empty() && !is_var_runtime_size_array(var);
 
 					    uint32_t desc_set = get_decoration(var_id, DecorationDescriptorSet);
 					    if (descriptor_set_is_argument_buffer(desc_set))
@@ -14056,7 +14064,7 @@ uint32_t CompilerMSL::get_metal_resource_index(SPIRVariable &var, SPIRType::Base
 	}
 	else
 	{
-		if (is_runtime_size_array(type))
+		if (is_var_runtime_size_array(var))
 		{
 			basetype = SPIRType::Struct;
 			binding_stride = 1;
@@ -14214,7 +14222,7 @@ string CompilerMSL::argument_decl(const SPIRFunction::Parameter &arg)
 		else
 			decl = join(cv_qualifier, type_to_glsl(type, arg.id));
 	}
-	else if (is_runtime_size_array(type))
+	else if (is_var_runtime_size_array(var))
 	{
 		const auto *parent_type = &get<SPIRType>(type.parent_type);
 		auto type_name = type_to_glsl(*parent_type, arg.id);
@@ -14316,7 +14324,7 @@ string CompilerMSL::argument_decl(const SPIRFunction::Parameter &arg)
 				decl += join("[", array_size, "]");
 			}
 		}
-		else if (is_runtime_size_array(type))
+		else if (is_var_runtime_size_array(var))
 		{
 			decl += " " + to_expression(name_id);
 		}
@@ -14366,7 +14374,7 @@ string CompilerMSL::argument_decl(const SPIRFunction::Parameter &arg)
 	}
 	else if (type_is_image || type_is_tlas)
 	{
-		if (is_runtime_size_array(type))
+		if (is_var_runtime_size_array(var))
 		{
 			decl = address_space + " " + decl + " " + to_expression(name_id);
 		}

spirv_msl.hpp

@@ -970,6 +970,7 @@ class CompilerMSL : public CompilerGLSL
 	void emit_specialization_constants_and_structs();
 	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;
 
 	void fix_up_shader_inputs_outputs();