Better IPA shader instruction implementation (#1082)

* Fix varying interpolation on fragment shader

* Some nits

* Alignment

1 files changed, 16 insertions, 6 deletions

diff --git a/Ryujinx.Graphics.Shader/Instructions/InstEmitMemory.cs b/Ryujinx.Graphics.Shader/Instructions/InstEmitMemory.cs
index 1fddcc8c..7eb88883 100644
--- a/Ryujinx.Graphics.Shader/Instructions/InstEmitMemory.cs
+++ b/Ryujinx.Graphics.Shader/Instructions/InstEmitMemory.cs
@@ -96,17 +96,27 @@ namespace Ryujinx.Graphics.Shader.Instructions
         {
             OpCodeIpa op = (OpCodeIpa)context.CurrOp;
 
-            InterpolationQualifier iq = InterpolationQualifier.None;
+            Operand res = Attribute(op.AttributeOffset);
 
-            switch (op.Mode)
+            if (op.AttributeOffset >= AttributeConsts.UserAttributeBase &&
+                op.AttributeOffset <  AttributeConsts.UserAttributeEnd)
             {
-                case InterpolationMode.Constant: iq = InterpolationQualifier.Flat;          break;
-                case InterpolationMode.Pass:     iq = InterpolationQualifier.NoPerspective; break;
+                int index = (op.AttributeOffset - AttributeConsts.UserAttributeBase) >> 4;
+
+                if (context.Config.ImapTypes[index].GetFirstUsedType() == PixelImap.Perspective)
+                {
+                    res = context.FPMultiply(res, Attribute(AttributeConsts.PositionW));
+                }
             }
+ 
+            if (op.Mode == InterpolationMode.Default)
+            {
+                Operand srcB = GetSrcB(context);
 
-            Operand srcA = Attribute(op.AttributeOffset, iq);
+                res = context.FPMultiply(res, srcB);
+            }
 
-            Operand res = context.FPSaturate(srcA, op.Saturate);
+            res = context.FPSaturate(res, op.Saturate);
 
             context.Copy(GetDest(context), res);
         }