maxwell_3d: Add viewport swizzles

src/video_core/engines/maxwell_3d.cpp

@@ -44,6 +44,12 @@ void Maxwell3D::InitializeRegisterDefaults() {
         viewport.depth_range_near = 0.0f;
         viewport.depth_range_far = 1.0f;
     }
+    for (auto& viewport : regs.viewport_transform) {
+        viewport.swizzle.x.Assign(Regs::ViewportSwizzle::PositiveX);
+        viewport.swizzle.y.Assign(Regs::ViewportSwizzle::PositiveY);
+        viewport.swizzle.z.Assign(Regs::ViewportSwizzle::PositiveZ);
+        viewport.swizzle.w.Assign(Regs::ViewportSwizzle::PositiveW);
+    }
 
     // Doom and Bomberman seems to use the uninitialized registers and just enable blend
     // so initialize blend registers with sane values

src/video_core/engines/maxwell_3d.h

@@ -575,6 +575,17 @@ public:
             Replay = 3,
         };
 
+        enum class ViewportSwizzle : u32 {
+            PositiveX = 0,
+            NegativeX = 1,
+            PositiveY = 2,
+            NegativeY = 3,
+            PositiveZ = 4,
+            NegativeZ = 5,
+            PositiveW = 6,
+            NegativeW = 7,
+        };
+
         struct RenderTargetConfig {
             u32 address_high;
             u32 address_low;
@@ -618,7 +629,13 @@ public:
             f32 translate_x;
             f32 translate_y;
             f32 translate_z;
-            INSERT_UNION_PADDING_WORDS(2);
+            union {
+                BitField<0, 3, ViewportSwizzle> x;
+                BitField<4, 3, ViewportSwizzle> y;
+                BitField<8, 3, ViewportSwizzle> z;
+                BitField<12, 3, ViewportSwizzle> w;
+            } swizzle;
+            INSERT_UNION_PADDING_WORDS(1);
 
             Common::Rectangle<f32> GetRect() const {
                 return {