Fix CC_HAS_ASM_GOTO_OUTPUT on non-x86 architectures

There's a silly problem with the CC_HAS_ASM_GOTO_OUTPUT test: even with
a working compiler it will fail on some architectures simply because it
uses the mnemonic "jmp" for testing the inline asm.

And as reported by Geert, not all architectures use that mnemonic, so
the test fails spuriously on such platforms (including arm and riscv,
but also several other architectures).

This issue avoided any obvious test failures because the build still
works thanks to falling back on the old non-asm-goto code, which just
generates worse code.

Just use an empty asm statement instead.

Reported-and-tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Fixes: e2ffa15b9baa ("kbuild: Disable CC_HAS_ASM_GOTO_OUTPUT on clang < 17")
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/init/Kconfig b/init/Kconfig
index ecddb94..6a91ec7 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -102,7 +102,7 @@ config CC_HAS_ASM_GOTO_OUTPUT
        # Detect basic support
        depends on $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
        # Detect clang (< v17) scoped label issues
-       depends on $(success,echo 'void b(void **);void* c(void);int f(void){{asm goto("jmp %l0"::::l0);return 0;l0:return 1;}void *x __attribute__((cleanup(b)))=c();{asm goto("jmp %l0"::::l1);return 2;l1:return 3;}}' | $(CC) -x c - -c -o /dev/null)
+       depends on $(success,echo 'void b(void **);void* c(void);int f(void){{asm goto(""::::l0);return 0;l0:return 1;}void *x __attribute__((cleanup(b)))=c();{asm goto(""::::l1);return 2;l1:return 3;}}' | $(CC) -x c - -c -o /dev/null)
 
 config CC_HAS_ASM_GOTO_TIED_OUTPUT
        depends on CC_HAS_ASM_GOTO_OUTPUT