Fix IoMap variable names

Output struct

Lazy Vertex IO

Output fixes

Fix output struct definition

MSL Binding Model description

Might need tweaks/adjustments

Cleanup

Typo + Format

src/Ryujinx.Graphics.Shader/CodeGen/Msl/Declarations.cs

@@ -3,14 +3,41 @@ using Ryujinx.Graphics.Shader.StructuredIr;
 using Ryujinx.Graphics.Shader.Translation;
 using System;
 using System.Collections.Generic;
-using System.Data.Common;
 using System.Linq;
-using System.Numerics;
 
 namespace Ryujinx.Graphics.Shader.CodeGen.Msl
 {
     static class Declarations
     {
+        /*
+         * Description of MSL Binding Strategy
+         *
+         * There are a few fundamental differences between how GLSL and MSL handle I/O.
+         * This comment will set out to describe the reasons why things are done certain ways
+         * and to describe the overall binding model that we're striving for here.
+         *
+         * Main I/O Structs
+         *
+         * Each stage will have a main input and output struct labeled as [Stage][In/Out], i.e VertexIn.
+         * Every attribute within these structs will be labeled with an [[attribute(n)]] property,
+         * and the overall struct will be labeled with [[stage_in]] for input structs, and defined as the
+         * output type of the main shader function for the output struct. This struct also contains special
+         * attribute-based properties like [[position]], therefore these are not confined to 'user-defined' variables.
+         *
+         * Samplers & Textures
+         *
+         * Metal does not have a combined image sampler like sampler2D in GLSL, as a result we need to bind
+         * an individual texture and a sampler object for each instance of a combined image sampler.
+         * Therefore, the binding indices of straight up textures (i.e. without a sampler) must start
+         * after the last sampler/texture pair (n + Number of Pairs).
+         *
+         * Uniforms
+         *
+         * MSL does not have a concept of uniforms comparable to that of GLSL. As a result, instead of
+         * being declared outside of any function body, uniforms are part of the function signature in MSL.
+         * This applies to anything bound to the shader not included in the main I/O structs.
+         */
+
         public static void Declare(CodeGenContext context, StructuredProgramInfo info)
         {
             context.AppendLine("#include <metal_stdlib>");
@@ -25,6 +52,8 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl
             }
 
             DeclareInputAttributes(context, info.IoDefinitions.Where(x => IsUserDefined(x, StorageKind.Input)));
+            context.AppendLine();
+            DeclareOutputAttributes(context, info.IoDefinitions.Where(x => x.StorageKind == StorageKind.Output));
         }
 
         static bool IsUserDefined(IoDefinition ioDefinition, StorageKind storageKind)
@@ -32,8 +61,13 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl
             return ioDefinition.StorageKind == storageKind && ioDefinition.IoVariable == IoVariable.UserDefined;
         }
 
-        public static void DeclareLocals(CodeGenContext context, StructuredFunction function)
+        public static void DeclareLocals(CodeGenContext context, StructuredFunction function, ShaderStage stage)
         {
+            if (stage == ShaderStage.Vertex)
+            {
+                context.AppendLine("VertexOutput out;");
+            }
+
             foreach (AstOperand decl in function.Locals)
             {
                 string name = context.OperandManager.DeclareLocal(decl);
@@ -107,5 +141,48 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl
                 }
             }
         }
+
+        private static void DeclareOutputAttributes(CodeGenContext context, IEnumerable<IoDefinition> inputs)
+        {
+            if (context.Definitions.IaIndexing)
+            {
+                // Not handled
+            }
+            else
+            {
+                if (inputs.Any())
+                {
+                    string prefix = "";
+
+                    switch (context.Definitions.Stage)
+                    {
+                        case ShaderStage.Vertex:
+                            prefix = "Vertex";
+                            break;
+                        case ShaderStage.Fragment:
+                            prefix = "Fragment";
+                            break;
+                        case ShaderStage.Compute:
+                            prefix = "Compute";
+                            break;
+                    }
+
+                    context.AppendLine($"struct {prefix}Output");
+                    context.EnterScope();
+
+                    foreach (var ioDefinition in inputs.OrderBy(x => x.Location))
+                    {
+                        string type = GetVarTypeName(context, context.Definitions.GetUserDefinedType(ioDefinition.Location, isOutput: true));
+                        string name = $"{DefaultNames.OAttributePrefix}{ioDefinition.Location}";
+                        name = ioDefinition.IoVariable == IoVariable.Position ? "position" : name;
+                        string suffix = ioDefinition.IoVariable == IoVariable.Position ? " [[position]]" : "";
+
+                        context.AppendLine($"{type} {name}{suffix};");
+                    }
+
+                    context.LeaveScope(";");
+                }
+            }
+        }
     }
 }

src/Ryujinx.Graphics.Shader/CodeGen/Msl/Instructions/InstGen.cs

@@ -70,6 +70,10 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl.Instructions
                 {
                     return $"{op} {GetSourceExpr(context, operation.GetSource(0), context.CurrentFunction.ReturnType)}";
                 }
+                else if (inst == Instruction.Return && context.Definitions.Stage == ShaderStage.Vertex)
+                {
+                    return $"{op} out";
+                }
 
                 int arity = (int)(info.Type & InstType.ArityMask);
 

src/Ryujinx.Graphics.Shader/CodeGen/Msl/Instructions/IoMap.cs

@@ -25,7 +25,7 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl.Instructions
                 IoVariable.InstanceId => ("instance_id", AggregateType.S32),
                 IoVariable.PointCoord => ("point_coord", AggregateType.Vector2),
                 IoVariable.PointSize => ("point_size", AggregateType.FP32),
-                IoVariable.Position => ("position", AggregateType.Vector4 | AggregateType.FP32),
+                IoVariable.Position => ("out.position", AggregateType.Vector4 | AggregateType.FP32),
                 IoVariable.PrimitiveId => ("primitive_id", AggregateType.S32),
                 IoVariable.UserDefined => GetUserDefinedVariableName(definitions, location, component, isOutput, isPerPatch),
                 IoVariable.VertexId => ("vertex_id", AggregateType.S32),
@@ -52,21 +52,7 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl.Instructions
                 name += "_" + "xyzw"[component & 3];
             }
 
-            string prefix = "";
-            switch (definitions.Stage)
-            {
-                case ShaderStage.Vertex:
-                    prefix = "Vertex";
-                    break;
-                case ShaderStage.Fragment:
-                    prefix = "Fragment";
-                    break;
-                case ShaderStage.Compute:
-                    prefix = "Compute";
-                    break;
-            }
-
-            prefix += isOutput ? "Out" : "In";
+            string prefix = isOutput ? "out" : "in";
 
             return (prefix + "." + name, definitions.GetUserDefinedType(location, isOutput));
         }

src/Ryujinx.Graphics.Shader/CodeGen/Msl/MslGenerator.cs

@@ -51,7 +51,7 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl
             context.AppendLine(GetFunctionSignature(context, function, stage, isMainFunc));
             context.EnterScope();
 
-            Declarations.DeclareLocals(context, function);
+            Declarations.DeclareLocals(context, function, stage);
 
             PrintBlock(context, function.MainBlock, isMainFunc);
 
@@ -77,6 +77,7 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl
 
             string funcKeyword = "inline";
             string funcName = null;
+            string returnType = Declarations.GetVarTypeName(context, function.ReturnType);
 
             if (isMainFunc)
             {
@@ -84,6 +85,7 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl
                 {
                     funcKeyword = "vertex";
                     funcName = "vertexMain";
+                    returnType = "VertexOutput";
                 }
                 else if (stage == ShaderStage.Fragment)
                 {
@@ -112,7 +114,7 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Msl
                 }
             }
 
-            return $"{funcKeyword} {Declarations.GetVarTypeName(context, function.ReturnType)} {funcName ?? function.Name}({string.Join(", ", args)})";
+            return $"{funcKeyword} {returnType} {funcName ?? function.Name}({string.Join(", ", args)})";
         }
 
         private static void PrintBlock(CodeGenContext context, AstBlock block, bool isMainFunction)