[tip:perf/core] tools/perf/build: Add 'autodep' functionality, generate feature test dependencies automatically

[tip:perf/core] tools/perf/build: Add 'autodep' functionality, generate feature test dependencies automatically

[tip-bot for Ingo Molnar]

Commit-ID:  8b6eb56a9570001634df1d2c7f38e7179a357362
Gitweb:     http://git.kernel.org/tip/8b6eb56a9570001634df1d2c7f38e7179a357362
Author:     Ingo Molnar <mingo@kernel.org>
AuthorDate: Mon, 30 Sep 2013 13:51:28 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 9 Oct 2013 08:48:29 +0200

tools/perf/build: Add 'autodep' functionality, generate feature test dependencies automatically

Use GCC's -MD feature to generate a dependency file for each feature test .c file,
and include that .d file in the config/feature-checks/Makefile.

This allows us to do two things:

 - speed up feature tests
 - detect removal or changes in build dependencies - including system libraries/headers

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-Jfma8pmPnnqzpxjbs3hpgmsj@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/perf/config/feature-checks/Makefile | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/config/feature-checks/Makefile b/tools/perf/config/feature-checks/Makefile
index b3f6372..4708cca 100644
--- a/tools/perf/config/feature-checks/Makefile
+++ b/tools/perf/config/feature-checks/Makefile
@@ -1,16 +1,20 @@
 
 FILES=test-hello
 
+CC := $(CC) -MD
+
 all: $(FILES)
 
 BUILD = $(CC) -o $(OUTPUT)$@ $@.c
 
 ###############################
 
-test-hello: test-hello.c
+test-hello:
 	$(BUILD)
 
+-include *.d */*.d
+
 ###############################
 
 clean:
-	rm -f $(FILES)
+	rm -f $(FILES) *.d