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    Subject[PATCH v7 4/6] 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>
    ---
    arch/Kconfig | 12 +++++
    scripts/Makefile.gcc-plugins | 2 +
    scripts/gcc-plugins/Makefile | 4 ++
    scripts/gcc-plugins/cyc_complexity_plugin.c | 73 +++++++++++++++++++++++++++++
    4 files changed, 91 insertions(+)
    create mode 100644 scripts/gcc-plugins/cyc_complexity_plugin.c

    diff --git a/arch/Kconfig b/arch/Kconfig
    index 7c12571..ddf29b4 100644
    --- a/arch/Kconfig
    +++ b/arch/Kconfig
    @@ -366,6 +366,18 @@ menuconfig GCC_PLUGINS
    GCC plugins are loadable modules that provide extra features to the
    compiler. They are useful for runtime instrumentation and static analysis.

    +config GCC_PLUGIN_CYC_COMPLEXITY
    + bool "Compute the cyclomatic complexity of a function"
    + depends on GCC_PLUGINS
    + help
    + 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).
    +
    config HAVE_CC_STACKPROTECTOR
    bool
    help
    diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
    index e6d66e2..282d63a 100644
    --- a/scripts/Makefile.gcc-plugins
    +++ b/scripts/Makefile.gcc-plugins
    @@ -2,6 +2,8 @@ ifdef CONFIG_GCC_PLUGINS
    __PLUGINCC := $(call cc-ifversion, -ge, 0408, $(HOSTCXX), $(HOSTCC))
    PLUGINCC := $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-plugin.sh "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)")

    + gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) += cyc_complexity_plugin.so
    +
    GCC_PLUGINS_CFLAGS := $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y))

    ifeq ($(PLUGINCC),)
    diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
    index b2d64af..31c72bf 100644
    --- a/scripts/gcc-plugins/Makefile
    +++ b/scripts/gcc-plugins/Makefile
    @@ -12,4 +12,8 @@ endif

    export GCCPLUGINS_DIR HOSTLIBS

    +$(HOSTLIBS)-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) := cyc_complexity_plugin.so
    +
    always := $($(HOSTLIBS)-y)
    +
    +cyc_complexity_plugin-objs := cyc_complexity_plugin.o
    diff --git a/scripts/gcc-plugins/cyc_complexity_plugin.c b/scripts/gcc-plugins/cyc_complexity_plugin.c
    new file mode 100644
    index 0000000..34df974
    --- /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;
    +}
    --
    2.4.1
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