linux-kernel - [PATCH 6/8] perf test coresight: Dismiss clang warning for unroll loop thread

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Message-Id: <20250925-perf_build_android_ndk-v1-6-8b35aadde3dc@arm.com>
Date: Thu, 25 Sep 2025 11:26:30 +0100
From: Leo Yan <leo.yan@....com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
 Quentin Monnet <qmo@...nel.org>, Andrii Nakryiko <andrii@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 James Clark <james.clark@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, 
 llvm@...ts.linux.dev, bpf@...r.kernel.org, Leo Yan <leo.yan@....com>
Subject: [PATCH 6/8] perf test coresight: Dismiss clang warning for unroll
 loop thread

clang-18.1.3 on Ubuntu 24.04.2 reports warning:

  unroll_loop_thread.c:35:25: warning: value size does not match register size specified by the constraint and modifier [-Wasm-operand-widths]
     35 |                         : /* in */ [in] "r" (in)
        |                                              ^
  unroll_loop_thread.c:39:1: warning: non-void function does not return a value [-Wreturn-type]
     39 | }
        | ^

Use the modifier "w" for 32-bit register access and return NULL at the
end of thread function.

Signed-off-by: Leo Yan <leo.yan@....com>
---
 .../tests/shell/coresight/unroll_loop_thread/unroll_loop_thread.c     | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/shell/coresight/unroll_loop_thread/unroll_loop_thread.c b/tools/perf/tests/shell/coresight/unroll_loop_thread/unroll_loop_thread.c
index 0fc7bf1a25af3607b40f091f62176134ddb7f9f6..8f4e1c985ca38ab545a05189432a14a6d888d34c 100644
--- a/tools/perf/tests/shell/coresight/unroll_loop_thread/unroll_loop_thread.c
+++ b/tools/perf/tests/shell/coresight/unroll_loop_thread/unroll_loop_thread.c
@@ -20,7 +20,7 @@ static void *thrfn(void *arg)
 	for (i = 0; i < 10000; i++) {
 		asm volatile (
 // force an unroll of thia add instruction so we can test long runs of code
-#define SNIP1 "add %[in], %[in], #1\n"
+#define SNIP1 "add %w[in], %w[in], #1\n"
 // 10
 #define SNIP2 SNIP1 SNIP1 SNIP1 SNIP1 SNIP1 SNIP1 SNIP1 SNIP1 SNIP1 SNIP1
 // 100
@@ -36,6 +36,8 @@ static void *thrfn(void *arg)
 			: /* clobber */
 		);
 	}
+
+	return NULL;
 }
 
 static pthread_t new_thr(void *(*fn) (void *arg), void *arg)

-- 
2.34.1