Function PatchVpos

shadercompiler/EffectCompilerMetal.cpp:2504–2574

Patches VPOS usages for pixel shaders: a common Dx9 legacy pattern of passing both POSITION (from vertex shader) and VPOS. Function remaps VPOS inputs to POSION so that there are no duplicate semantics in the stage_in struct.

// vertex shader) and VPOS. Function remaps VPOS inputs to POSION so that there are no duplicate semantics
// in the stage_in struct.
bool PatchVpos( ParserState& state, ASTNode* inputsStruct, std::vector<ASTNode*>& argumentAccessors )
{
	Type float4 = TypeFromTokenType( OP_FLOAT );
	float4.width = 4;

	// First find POSITION input
	ASTNode* position = nullptr;
	size_t positionIndex = 0;
	for( size_t index = 0; index < inputsStruct->GetChildrenCount(); ++index )
	{
		auto child = inputsStruct->GetChild( index );
		auto member = child->GetChild( 0 );
		if( IEquals( member->GetSymbol()->semantic, "SV_Position" ) || IEquals( member->GetSymbol()->semantic, "POSITION" ) || IEquals( member->GetSymbol()->semantic, "POSITION0" ) )
		{
			if( child->GetType() != float4 )
			{
				state.ShowMessage( EC_CUSTOM_ERROR, "Pixel shader %s input needs to be a float4", ToString( member->GetSymbol()->semantic ).c_str() );
				return false;
			}
			position = child;
			positionIndex = index;
			break;
		}
	}

	// Find any other POSITION/VPOS inputs and remap them to the first POSITION
	for( size_t index = 0; index < inputsStruct->GetChildrenCount(); ++index )
	{
		auto child = inputsStruct->GetChild( index );
		if( child == position )
		{
			continue;
		}
		auto member = child->GetChild( 0 );
		if( IEquals( member->GetSymbol()->semantic, "SV_Position" ) || IEquals( member->GetSymbol()->semantic, "POSITION" ) || IEquals( member->GetSymbol()->semantic, "POSITION0" ) || IEquals( member->GetSymbol()->semantic, "VPOS" ) )
		{
			if( !child->GetType().IsScalarOrVector() || child->GetType().builtInType != OP_FLOAT )
			{
				state.ShowMessage( EC_CUSTOM_ERROR, "Pixel shader %s input needs to be a float vector", ToString( member->GetSymbol()->semantic ).c_str() );
				return false;
			}
			if( position )
			{
				if( position->GetType() != child->GetType() )
				{
					const char* swizzles = "xyzw";
					argumentAccessors[index] = NewDot( state,
													   argumentAccessors[positionIndex]->Copy(),
													   MakeInlineString( swizzles, swizzles + 4 - child->GetType().width ) );
				}
				else
				{
					argumentAccessors[index] = argumentAccessors[positionIndex]->Copy();
				}
				inputsStruct->RemoveChild( index );
				--index;
			}
			else if( child->GetType().width != 4 )