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/CodeGen/Glsl/Instructions/InstGenCall.cs

@@ -0,0 +1,29 @@
+using Ryujinx.Graphics.Shader.IntermediateRepresentation;
+using Ryujinx.Graphics.Shader.StructuredIr;
+using System.Diagnostics;
+
+using static Ryujinx.Graphics.Shader.CodeGen.Glsl.Instructions.InstGenHelper;
+
+namespace Ryujinx.Graphics.Shader.CodeGen.Glsl.Instructions
+{
+    static class InstGenCall
+    {
+        public static string Call(CodeGenContext context, AstOperation operation)
+        {
+            AstOperand funcId = (AstOperand)operation.GetSource(0);
+
+            Debug.Assert(funcId.Type == OperandType.Constant);
+
+            var function = context.GetFunction(funcId.Value);
+
+            string[] args = new string[operation.SourcesCount - 1];
+
+            for (int i = 0; i < args.Length; i++)
+            {
+                args[i] = GetSoureExpr(context, operation.GetSource(i + 1), function.GetArgumentType(i));
+            }
+
+            return $"{function.Name}({string.Join(", ", args)})";
+        }
+    }
+}