Add Cyclomatic complexity GCC plugin

Add a very simple plugin to demonstrate the GCC plugin infrastructure. This GCC
plugin computes the cyclomatic complexity of each function.

The complexity M of a function's control flow graph is defined as:
M = E - N + 2P
where
E = the number of edges
N = the number of nodes
P = the number of connected components (exit nodes).

Signed-off-by: Emese Revfy <re.emese@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michal Marek <mmarek@suse.com>

2 files changed, 74 insertions, 0 deletions

diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
index a4c93419d5d1..c60ba4bef57c 100644
--- a/scripts/gcc-plugins/Makefile
+++ b/scripts/gcc-plugins/Makefile
@@ -17,4 +17,5 @@ export GCCPLUGINS_DIR HOSTLIBS
 $(HOSTLIBS)-y := $(GCC_PLUGIN)
 always := $($(HOSTLIBS)-y)
 
+cyc_complexity_plugin-objs := cyc_complexity_plugin.o
 clean-files += *.so
diff --git a/scripts/gcc-plugins/cyc_complexity_plugin.c b/scripts/gcc-plugins/cyc_complexity_plugin.c
new file mode 100644
index 000000000000..34df974c6ba3
--- /dev/null
+++ b/scripts/gcc-plugins/cyc_complexity_plugin.c
@@ -0,0 +1,73 @@
+/*
+ * Copyright 2011-2016 by Emese Revfy <re.emese@gmail.com>
+ * Licensed under the GPL v2, or (at your option) v3
+ *
+ * Homepage:
+ * https://github.com/ephox-gcc-plugins/cyclomatic_complexity
+ *
+ * http://en.wikipedia.org/wiki/Cyclomatic_complexity
+ * The complexity M is then defined as:
+ * M = E - N + 2P
+ * where
+ *
+ *  E = the number of edges of the graph
+ *  N = the number of nodes of the graph
+ *  P = the number of connected components (exit nodes).
+ *
+ * Usage (4.5 - 5):
+ * $ make clean; make run
+ */
+
+#include "gcc-common.h"
+
+int plugin_is_GPL_compatible;
+
+static struct plugin_info cyc_complexity_plugin_info = {
+        .version        = "20160225",
+        .help           = "Cyclomatic Complexity\n",
+};
+
+static unsigned int cyc_complexity_execute(void)
+{
+        int complexity;
+        expanded_location xloc;
+
+        /* M = E - N + 2P */
+        complexity = n_edges_for_fn(cfun) - n_basic_blocks_for_fn(cfun) + 2;
+
+        xloc = expand_location(DECL_SOURCE_LOCATION(current_function_decl));
+        fprintf(stderr, "Cyclomatic Complexity %d %s:%s\n", complexity,
+                xloc.file, DECL_NAME_POINTER(current_function_decl));
+
+        return 0;
+}
+
+#define PASS_NAME cyc_complexity
+
+#define NO_GATE
+#define TODO_FLAGS_FINISH TODO_dump_func
+
+#include "gcc-generate-gimple-pass.h"
+
+int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
+{
+        const char * const plugin_name = plugin_info->base_name;
+        struct register_pass_info cyc_complexity_pass_info;
+
+        cyc_complexity_pass_info.pass                           = make_cyc_complexity_pass();
+        cyc_complexity_pass_info.reference_pass_name            = "ssa";
+        cyc_complexity_pass_info.ref_pass_instance_number       = 1;
+        cyc_complexity_pass_info.pos_op                         = PASS_POS_INSERT_AFTER;
+
+        if (!plugin_default_version_check(version, &gcc_version)) {
+                error(G_("incompatible gcc/plugin versions"));
+                return 1;
+        }
+
+        register_callback(plugin_name, PLUGIN_INFO, NULL,
+                                &cyc_complexity_plugin_info);
+        register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
+                                &cyc_complexity_pass_info);
+
+        return 0;
+}