[PATCH bpf-next v3 11/14] tools build: Implement feature check for BPF atomics in Clang

[Brendan Jackman <jackmanb@xxxxxxxxxx>]

Change-Id: Ia15bb76f7152fff2974e38242d7430ce2987a71e

Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Cc: "Frank Ch. Eigler" <fche@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Thomas Hebb <tommyhebb@xxxxxxxxx>
Change-Id: Ie2c3832eaf050d627764071d1927c7546e7c4b4b
Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
---
 tools/build/feature/Makefile                 | 4 ++++
 tools/build/feature/test-clang-bpf-atomics.c | 9 +++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 tools/build/feature/test-clang-bpf-atomics.c

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index cdde783f3018..81370d7fa193 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -70,6 +70,7 @@ FILES=                                          \
          test-libaio.bin			\
          test-libzstd.bin			\
          test-clang-bpf-co-re.bin		\
+         test-clang-bpf-atomics.bin		\
          test-file-handle.bin			\
          test-libpfm4.bin
 
@@ -331,6 +332,9 @@ $(OUTPUT)test-clang-bpf-co-re.bin:
 	$(CLANG) -S -g -target bpf -o - $(patsubst %.bin,%.c,$(@F)) |	\
 		grep BTF_KIND_VAR
 
+$(OUTPUT)test-clang-bpf-atomics.bin:
+	$(CLANG) -S -g -target bpf -mcpu=v3 -Werror=implicit-function-declaration -o - $(patsubst %.bin,%.c,$(@F)) 2>&1
+
 $(OUTPUT)test-file-handle.bin:
 	$(BUILD)
 
diff --git a/tools/build/feature/test-clang-bpf-atomics.c b/tools/build/feature/test-clang-bpf-atomics.c
new file mode 100644
index 000000000000..8b5fcdd4ba6f
--- /dev/null
+++ b/tools/build/feature/test-clang-bpf-atomics.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Google
+
+int x = 0;
+
+int foo(void)
+{
+	return __sync_val_compare_and_swap(&x, 1, 2);
+}
-- 
2.29.2.454.gaff20da3a2-goog