Implement CAL and RET shader instructions (#1618)

* Add support for CAL and RET shader instructions

* Remove unused stuff

* Fix a bug that could cause the wrong values to be passed to a function

* Avoid repopulating function id dictionary every time

* PR feedback

* Fix vertex shader A/B merge

Ryujinx.Graphics.Shader/StructuredIr/StructuredFunction.cs

@@ -0,0 +1,41 @@
+using System.Collections.Generic;
+
+namespace Ryujinx.Graphics.Shader.StructuredIr
+{
+    class StructuredFunction
+    {
+        public AstBlock MainBlock { get; }
+
+        public string Name { get; }
+
+        public VariableType ReturnType { get; }
+
+        public VariableType[] InArguments { get; }
+        public VariableType[] OutArguments { get; }
+
+        public HashSet<AstOperand> Locals { get; }
+
+        public StructuredFunction(
+            AstBlock mainBlock,
+            string name,
+            VariableType returnType,
+            VariableType[] inArguments,
+            VariableType[] outArguments)
+        {
+            MainBlock = mainBlock;
+            Name = name;
+            ReturnType = returnType;
+            InArguments = inArguments;
+            OutArguments = outArguments;
+
+            Locals = new HashSet<AstOperand>();
+        }
+
+        public VariableType GetArgumentType(int index)
+        {
+            return index >= InArguments.Length
+                ? OutArguments[index - InArguments.Length]
+                : InArguments[index];
+        }
+    }
+}