Cycles: OpenCL Performance

When using OpenCL with Cycles the rendering time increased substantial.
After doing some tests the bottleneck was found in 4d voronoi and 2d and
3d smooth voronoi.

This change will hide these behind a specific compile directive so the
speed will improve.

AMD RX480 + BMW scene

    2.80 (3:10)
    2.81 (5:48)
    2.81 excluding 4d voronoi+2d/3d smooth (3:50)

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D6231

intern/cycles/kernel/svm/svm_voronoi.h

@@ -986,6 +986,7 @@ ccl_device void svm_node_tex_voronoi(KernelGlobals *kg,
                         &color_out,
                         &position_out_2d);
           break;
+#if NODES_FEATURE(NODE_FEATURE_VORONOI_EXTRA)
         case NODE_VORONOI_SMOOTH_F1:
           voronoi_smooth_f1_2d(coord_2d,
                                smoothness,
@@ -996,6 +997,7 @@ ccl_device void svm_node_tex_voronoi(KernelGlobals *kg,
                                &color_out,
                                &position_out_2d);
           break;
+#endif
         case NODE_VORONOI_F2:
           voronoi_f2_2d(coord_2d,
                         exponent,
@@ -1029,6 +1031,7 @@ ccl_device void svm_node_tex_voronoi(KernelGlobals *kg,
                         &color_out,
                         &position_out);
           break;
+#if NODES_FEATURE(NODE_FEATURE_VORONOI_EXTRA)
         case NODE_VORONOI_SMOOTH_F1:
           voronoi_smooth_f1_3d(coord,
                                smoothness,
@@ -1039,6 +1042,7 @@ ccl_device void svm_node_tex_voronoi(KernelGlobals *kg,
                                &color_out,
                                &position_out);
           break;
+#endif
         case NODE_VORONOI_F2:
           voronoi_f2_3d(coord,
                         exponent,
@@ -1060,6 +1064,8 @@ ccl_device void svm_node_tex_voronoi(KernelGlobals *kg,
       position_out = safe_divide_float3_float(position_out, scale);
       break;
     }
+
+#if NODES_FEATURE(NODE_FEATURE_VORONOI_EXTRA)
     case 4: {
       float4 coord_4d = make_float4(coord.x, coord.y, coord.z, w);
       float4 position_out_4d;
@@ -1106,6 +1112,7 @@ ccl_device void svm_node_tex_voronoi(KernelGlobals *kg,
       w_out = position_out_4d.w;
       break;
     }
+#endif
     default:
       kernel_assert(0);
   }