[PATCH] D65344: [analyzer] exploded-graph-rewriter: NFC: Replace explorers with trimmers.

[Artem Dergachev via Phabricator via cfe-commits]

NoQ created this revision.
NoQ added a reviewer: Charusso.
Herald added subscribers: cfe-commits, dkrupp, donat.nagy, Szelethus, mikhail.ramalho, a.sidorin, szepet, baloghadamsoftware, xazax.hun.
Herald added a project: clang.

Explorers aren't the right abstraction. For the purposes of displaying svg files we don't care in which order do we explore the nodes. We may care about this for other analyses, but we're not there yet.

The function of cutting out chunks of the graph is performed poorly by the explorers, because querying predecessors/successors on the explored nodes yields original successors/predecessors even if they aren't being explored.

Introduce a new entity, "trimmers", that do one thing but to it right: cut out chunks of the graph. Trimmers mutate the graph, so stale edges aren't even visible to their consumers in the pipeline. Additionally, trimmers are intrinsically composable: multiple trimmers can be applied to the graph sequentially.

Refactor the single-path explorer into the single-path trimmer. Rename the test file for consistency.


Repository:
  rC Clang

https://reviews.llvm.org/D65344

Files:
  clang/test/Analysis/exploded-graph-rewriter/explorers.dot
  clang/test/Analysis/exploded-graph-rewriter/trimmers.dot
  clang/utils/analyzer/exploded-graph-rewriter.py


Index: clang/utils/analyzer/exploded-graph-rewriter.py
===================================================================
--- clang/utils/analyzer/exploded-graph-rewriter.py
+++ clang/utils/analyzer/exploded-graph-rewriter.py
@@ -882,37 +882,36 @@
         visitor.visit_end_of_graph()
 
 
-# SinglePathExplorer traverses only a single path - the leftmost path
-# from the root. Useful when the trimmed graph is still too large
-# due to a large amount of equivalent reports.
-class SinglePathExplorer(object):
-    def __init__(self):
-        super(SinglePathExplorer, self).__init__()
+#===-----------------------------------------------------------------------===#
+# Trimmers cut out parts of the ExplodedGraph so that to focus on other parts.
+# Trimmers can be combined together by applying them sequentially.
+#===-----------------------------------------------------------------------===#
 
-    def explore(self, graph, visitor):
-        visitor.visit_begin_graph(graph)
 
-        # Keep track of visited nodes in order to avoid loops.
-        visited = set()
+# SinglePathTrimmer keeps only a single path - the leftmost path from the root.
+# from the root. Useful when the trimmed graph is still too large.
+class SinglePathTrimmer(object):
+    def __init__(self):
+        super(SinglePathTrimmer, self).__init__()
+
+    def trim(self, graph):
+        visited_nodes = set()
         node_id = graph.root_id
         while True:
-            visited.add(node_id)
+            visited_nodes.add(node_id)
             node = graph.nodes[node_id]
-            logging.debug('Visiting ' + node_id)
-            visitor.visit_node(node)
-            if len(node.successors) == 0:
-                break
-
-            succ_id = node.successors[0]
-            succ = graph.nodes[succ_id]
-            logging.debug('Visiting edge: %s -> %s ' % (node_id, succ_id))
-            visitor.visit_edge(node, succ)
-            if succ_id in visited:
+            if len(node.successors) > 0:
+                succ_id = node.successors[0]
+                succ = graph.nodes[succ_id]
+                node.successors = [succ_id]
+                succ.predecessors = [node_id]
+                if succ_id in visited_nodes:
+                    break
+                node_id = succ_id
+            else:
                 break
-
-            node_id = succ_id
-
-        visitor.visit_end_of_graph()
+        graph.nodes = {node_id: graph.nodes[node_id]
+                       for node_id in visited_nodes}
 
 
 #===-----------------------------------------------------------------------===#
@@ -960,10 +959,18 @@
             raw_line = raw_line.strip()
             graph.add_raw_line(raw_line)
 
-    explorer = SinglePathExplorer() if args.single_path else BasicExplorer()
+    trimmers = []
+    if args.single_path:
+        trimmers.append(SinglePathTrimmer())
+
+    explorer = BasicExplorer()
+
     visitor = DotDumpVisitor(args.diff, args.dark, args.gray, args.topology,
                              args.rewrite_only)
 
+    for trimmer in trimmers:
+        trimmer.trim(graph)
+
     explorer.explore(graph, visitor)
 
 


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