Function AutoAssignRegistersForNode

shadercompiler/EffectCompilerMetal.cpp:1754–2189

}

bool AutoAssignRegistersForNode( ParserState& state, ASTNode* functionHeader, const FileLocation& messageLocation )
{
	/*
		
		This function assigns "registers" i.e. Metal input attributes [[buffer(###)]] or [[texture(###)]] to the shader arguments.
		Metal partitions the set off all inputs into "buffers" and "textures", which is somewhat different from DirectX that partitions
		the inputs into "constant buffers", SRVs and UAVs. Since Trinity uses DirectX partitioning for inputs we need to adapt Metal
		to that. This puts some extra limitations on the allocation of registers. For metal we use a single set or "registers" (up to
		31 registers - the limit for min supported macOS): all SRV/UAV buffers and textures go into this set of "registers". Constant
		buffers are in a separate set. We map these to sets to "buffers" and "textures" for Metal.
		
		Firstly, we reserve 4 first slots in [[buffer(###)]] metal set for IA buffers
		Secondly, we reserve space in [[buffer(###)]] metal set for all constant buffers as they have an explicit register binding. We map
		them with an offset of 4, so for example the Globals constant buffer (cb0) would be mapped to [[buffer(4)]].
		Then we allocate any unused [[buffer(###)]] indices for SRV/UAV buffer inputs. For example, if [[buffer(5)]] is not assigned, the
		next SRV/UAV buffer gets assigned to that slot and also recieves SRV register #5 as if it was declared register(t5) in HLSL.
		Lastly we allocate SRV/UAV texture registers, making sure we don't put them into the same SRV "register" as a previously allocated
		SRV/UAV buffer.

		*/

	auto GetAssignedSymbolNames = []( const std::vector<Symbol*>& symbols ) {
		std::string result;
		for( auto symbol : symbols )
		{
			if( !result.empty() )
			{
				result += ", ";
			}
			result += ToString( symbol->name );
		}
		return result;
	};

	auto RecordRegister = [&state]( int index, std::vector<Symbol*>& registers, ASTNode* node ) {
		Symbol* symbol = node->GetSymbol();

		if( index < 0 || index >= int( registers.size() ) )
		{
			state.ShowMessage(
				node->GetLocation(),
				EC_CUSTOM_ERROR,
				"Couldn't allocate a register for %s. Reason: Invalid register index.",
				ToString( symbol->name ).c_str() );
			return false;
		}

		if( !registers[index] )
		{
			registers[index] = symbol;
			return true;
		}
		else
		{
			state.ShowMessage(
				node->GetLocation(),
				EC_CUSTOM_ERROR,
				"Couldn't allocate a register for %s. Reason: register %d already assigned to %s.",