Fix T46782: Updating Shaders very slow with complex nodegraph

The issue was caused by not really optimal graph traversal for gathering nodes
dependencies which could have exponential complexity with a long tree branches
connected with multiple connections between them.

Now we optimize the depth traversal and perform early output if the node was
already traversed.

Please note that this adds some limitations to the use of SVM compiler's
find_dependencies() in the cases when skip_node is not NULL and one wants to
perform dependencies find sequentially with the same set. This doesn't happen
in the code, but one should be aware of this.

1 files changed, 1 insertions, 1 deletions

diff --git a/intern/cycles/render/graph.cpp b/intern/cycles/render/graph.cpp
index 3e417d13d4d..e888cb37137 100644
--- a/intern/cycles/render/graph.cpp
+++ b/intern/cycles/render/graph.cpp
@@ -306,7 +306,7 @@ void ShaderGraph::find_dependencies(ShaderNodeSet& dependencies, ShaderInput *in
 	/* find all nodes that this input depends on directly and indirectly */
 	ShaderNode *node = (input->link)? input->link->parent: NULL;
 
-	if(node) {
+	if(node != NULL && dependencies.find(node) == dependencies.end()) {
 		foreach(ShaderInput *in, node->inputs)
 			find_dependencies(dependencies, in);