Matcher skip (#2169)

* Update cpu_external_function.cpp

* fix test case failures

* env var to abort matching

* Update matcher.cpp

* Update matcher.cpp

* add a comment

* give an env var a better name

src/ngraph/pattern/matcher.cpp

@@ -16,6 +16,7 @@
 
 #include "matcher.hpp"
 #include <algorithm>
+#include <regex>
 #include <typeindex>
 #include <typeinfo>
 
@@ -189,6 +190,21 @@ namespace ngraph
             add_node(graph_node);
             size_t watermark = m_matched_list.size() - 1;
 
+            // This env var allows one to specify node name patterns to abort pattern matching
+            // at particular nodes. The upshot is that one can quickly zero in on an offending fusion by
+            // disabling individual fusions or optimizations that use Matcher.
+            static const char* node_skip_cregex = std::getenv("NGRAPH_FAIL_MATCH_AT");
+            if (node_skip_cregex)
+            {
+                static const std::regex node_skip_regex(node_skip_cregex);
+                if (std::regex_match(graph_node->get_name(), node_skip_regex))
+                {
+                    NGRAPH_DEBUG << "[MATCHER] Aborting at " << graph_node->get_name()
+                                 << " due to NGRAPH_MATCHER_SKIP set to " << node_skip_cregex;
+                    return abort_match(watermark, false);
+                }
+            }
+
             NGRAPH_DEBUG << pad(2 * m_depth) << "[MATCHER] in match_node : "
                          << "pattern = " << pattern_node->get_name() << " matched "
                          << graph_node->get_name();