Function DetectUnusedArguments

shadercompiler/EffectCompilerMetal.cpp:4270–4344

Implements a disgusting method of funding which shader parameters turn out to be unused by the shader and emits warnings for them. Uses metal-objdump to disassemble the shader binary, finds a shader definition and looks through parameters. Parameters having "readnone" token are unused. Or so I think...

// Uses metal-objdump to disassemble the shader binary, finds a shader definition and looks through parameters.
// Parameters having "readnone" token are unused. Or so I think...
void DetectUnusedArguments( const char* libPath, ParserState& state, ASTNode* callNode )
{
	ZoneScoped;

	std::string entryName = ToString( callNode->GetChild( 1 )->GetSymbol()->name );
	auto functionHeader = callNode->GetChild( 1 )->GetSymbol()->definition->GetChild( 0 );

	for( auto child : functionHeader->GetChildren() )
	{
		if( child && child->GetSymbol() )
		{
			child->GetSymbol()->used = true;
		}
	}

	std::ostringstream cmd;
	cmd << MetalTool( "metal-objdump" ) << " -disassemble " << libPath;
	auto objdump = RunProcess( cmd.str().c_str() );
	if( objdump.first != 0 )
	{
		state.ShowMessage( callNode->GetLocation(), EC_CUSTOM_WARNING, "failed to run objdump, unused parameter information is unavailable" );
	}

	size_t argumentIndex = 0;
	size_t stageInIndex = 0;

	std::regex shader( "define.*@" + entryName + "(.*)" );
	std::smatch match;
	if( std::regex_search( objdump.second, match, shader ) )
	{
		auto args = match[1].str();
		SplitString( args, ',', [&]( auto arg ) {
			std::string argName = arg;
			Symbol* argumentSymbol = nullptr;

			if( argumentIndex < functionHeader->GetChildrenCount() )
			{
				argumentSymbol = functionHeader->GetChild( argumentIndex )->GetSymbol();

				bool isStageIn = false;
				for( auto reg : argumentSymbol->registerSpecifier )
				{
					if( reg.second.registerType == MetalRegister::StageIn )
					{
						isStageIn = true;
						break;
					}
				}

				argName = ToString( argumentSymbol->name );
				if( isStageIn )
				{
					argName += "." + ToString( functionHeader->GetChild( argumentIndex )->GetType().symbol->definition->GetChild( stageInIndex )->GetChild( 0 )->GetSymbol()->name );
					if( ++stageInIndex >= functionHeader->GetChild( argumentIndex )->GetType().symbol->definition->GetChildrenCount() )
					{
						++argumentIndex;
					}
				}