perf test coresight: Dismiss clang warning for thread loop

clang-18.1.3 on Ubuntu 24.04.2 reports warning:

  thread_loop.c:41:23: warning: value size does not match register size specified by the constraint and modifier [-Wasm-operand-widths]
     41 |                 : /* in */ [i] "r" (i), [len] "r" (len)
        |                                     ^
  thread_loop.c:37:8: note: use constraint modifier "w"
     37 |                 "add %[i], %[i], #1\n"
        |                      ^~~~
        |                      %w[i]
  thread_loop.c:41:23: warning: value size does not match register size specified by the constraint and modifier [-Wasm-operand-widths]
     41 |                 : /* in */ [i] "r" (i), [len] "r" (len)
        |                                     ^
  thread_loop.c:37:14: note: use constraint modifier "w"
     37 |                 "add %[i], %[i], #1\n"
        |                            ^~~~
        |                            %w[i]
  thread_loop.c:41:23: warning: value size does not match register size specified by the constraint and modifier [-Wasm-operand-widths]
     41 |                 : /* in */ [i] "r" (i), [len] "r" (len)
        |                                     ^
  thread_loop.c:38:8: note: use constraint modifier "w"
     38 |                 "cmp %[i], %[len]\n"
        |                      ^~~~
        |                      %w[i]
  thread_loop.c:41:38: warning: value size does not match register size specified by the constraint and modifier [-Wasm-operand-widths]
     41 |                 : /* in */ [i] "r" (i), [len] "r" (len)
        |                                                    ^
  thread_loop.c:38:14: note: use constraint modifier "w"
     38 |                 "cmp %[i], %[len]\n"
        |                            ^~~~~~
        |                            %w[len]

Use the modifier "w" for 32-bit register access.

Signed-off-by: Leo Yan <[email protected]>

Author: Leo-Yan

tools/perf/tests/shell/coresight/thread_loop/thread_loop.c

@@ -34,8 +34,8 @@ static void *thrfn(void *arg)
 	}
 	asm volatile(
 		"loop:\n"
-		"add %[i], %[i], #1\n"
-		"cmp %[i], %[len]\n"
+		"add %w[i], %w[i], #1\n"
+		"cmp %w[i], %w[len]\n"
 		"blt loop\n"
 		: /* out */
 		: /* in */ [i] "r" (i), [len] "r" (len)