perf clang: Add builtin clang support ant test case

Add basic clang support in clang.cpp and test__clang() testcase. The
first testcase checks if builtin clang is able to generate LLVM IR.

tests/clang.c is a proxy. Real testcase resides in
utils/c++/clang-test.cpp in c++ and exports C interface to perf test
subsystem.

Test result:

   $ perf test -v clang
   51: builtin clang support                               :
   51.1: Test builtin clang compile C source to IR              :
   --- start ---
   test child forked, pid 13215
   test child finished with 0
   ---- end ----
   Test builtin clang support subtest 0: Ok

Committer note:

Make sure you've enabled CLANG and LLVM builtin support by setting
the LIBCLANGLLVM variable on the make command line, e.g.:

  make LIBCLANGLLVM=1 O=/tmp/build/perf -C tools/perf install-bin

Otherwise you'll get this when trying to do the 'perf test' call above:

  # perf test clang
  51: builtin clang support                      : Skip (not compiled in)
  #

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Joe Stringer <joe@ovn.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/20161126070354.141764-11-wangnan0@huawei.com
[ Removed "Test" from descriptions, redundant and already removed from all the other entries ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/Build

@@ -43,6 +43,7 @@ perf-y += sdt.o
 perf-y += is_printable_array.o
 perf-y += bitmap.o
 perf-y += perf-hooks.o
+perf-y += clang.o
 
 $(OUTPUT)tests/llvm-src-base.c: tests/bpf-script-example.c tests/Build
 	$(call rule_mkdir)

tools/perf/tests/builtin-test.c

@@ -233,6 +233,15 @@ static struct test generic_tests[] = {
 		.desc = "perf hooks",
 		.func = test__perf_hooks,
 	},
+	{
+		.desc = "builtin clang support",
+		.func = test__clang,
+		.subtest = {
+			.skip_if_fail	= true,
+			.get_nr		= test__clang_subtest_get_nr,
+			.get_desc	= test__clang_subtest_get_desc,
+		}
+	},
 	{
 		.func = NULL,
 	},

tools/perf/tests/clang.c

@@ -0,0 +1,42 @@
+#include "tests.h"
+#include "debug.h"
+#include "util.h"
+#include "c++/clang-c.h"
+
+static struct {
+	int (*func)(void);
+	const char *desc;
+} clang_testcase_table[] = {
+#ifdef HAVE_LIBCLANGLLVM_SUPPORT
+	{
+		.func = test__clang_to_IR,
+		.desc = "builtin clang compile C source to IR",
+	},
+#endif
+};
+
+int test__clang_subtest_get_nr(void)
+{
+	return (int)ARRAY_SIZE(clang_testcase_table);
+}
+
+const char *test__clang_subtest_get_desc(int i)
+{
+	if (i < 0 || i >= (int)ARRAY_SIZE(clang_testcase_table))
+		return NULL;
+	return clang_testcase_table[i].desc;
+}
+
+#ifndef HAVE_LIBCLANGLLVM_SUPPORT
+int test__clang(int i __maybe_unused)
+{
+	return TEST_SKIP;
+}
+#else
+int test__clang(int i __maybe_unused)
+{
+	if (i < 0 || i >= (int)ARRAY_SIZE(clang_testcase_table))
+		return TEST_FAIL;
+	return clang_testcase_table[i].func();
+}
+#endif

tools/perf/tests/tests.h

@@ -92,6 +92,9 @@ int test__sdt_event(int subtest);
 int test__is_printable_array(int subtest);
 int test__bitmap_print(int subtest);
 int test__perf_hooks(int subtest);
+int test__clang(int subtest);
+const char *test__clang_subtest_get_desc(int subtest);
+int test__clang_subtest_get_nr(void);
 
 #if defined(__arm__) || defined(__aarch64__)
 #ifdef HAVE_DWARF_UNWIND_SUPPORT