[PATCH] m68k: libgcc: Fix lvalue abuse in umul_ppmm()

[PATCH] m68k: libgcc: Fix lvalue abuse in umul_ppmm()

[Geert Uytterhoeven]

    lib/muldi3.c:53:28: warning: asm output is not an lvalue
    lib/muldi3.c:53:28: warning: asm output is not an lvalue
    lib/muldi3.c:53:28: error: not addressable
    lib/muldi3.c:53:28: warning: generating address of non-lvalue (11)
    lib/muldi3.c:53:28: warning: generating address of non-lvalue (11)

Fix the lvalue warnings by replacing the casts on the output operands by
intermediate variables of the right type.

Fix the "not addressable" error by replacing the cast on the second
input operand by an intermediate variable, too.  Treat the other input
operand the same for consistency.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501030516.uZrwnuQQ-lkp@intel.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
To be queued in the m68k for-v6.14 branch.
Not folding into commit e96424b86d5098f4 ("m68k: Use kernel's generic
muldi3 libgcc function"), as the issue was pre-existing.
---
 arch/m68k/include/asm/libgcc.h | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/m68k/include/asm/libgcc.h b/arch/m68k/include/asm/libgcc.h
index 1cce6d130d805368..27e17195bd7be41c 100644
--- a/arch/m68k/include/asm/libgcc.h
+++ b/arch/m68k/include/asm/libgcc.h
@@ -10,11 +10,18 @@
  * will fallback to using the C-coded version of umul_ppmm().
  */
 #define umul_ppmm(w1, w0, u, v)				\
-	__asm__ ("mulu%.l %3,%1:%0"			\
-		 : "=d" ((unsigned long)(w0)),		\
-		   "=d" ((unsigned long)(w1))		\
-		 : "%0" ((unsigned long)(u)),		\
-		   "dmi" ((unsigned long)(v)))
+	do {						\
+		unsigned long __u = (u), __v = (v);	\
+		unsigned long __w0, __w1;		\
+							\
+		__asm__ ("mulu%.l %3,%1:%0"		\
+			 : "=d" (__w0),			\
+			   "=d" (__w1)			\
+			 : "%0" (__u),			\
+			   "dmi" (__v));		\
+							\
+		(w0) = __w0; (w1) = __w1;		\
+	} while (0)
 #endif /* !CONFIG_CPU_HAS_NO_MULDIV64 */
 
 #endif /* __ASM_M68K_LIBGCC_H */
-- 
2.43.0

Re: [PATCH] m68k: libgcc: Fix lvalue abuse in umul_ppmm()

[Greg Ungerer]

Hi Geert,

On 9/1/25 03:22, Geert Uytterhoeven wrote:
>      lib/muldi3.c:53:28: warning: asm output is not an lvalue
>      lib/muldi3.c:53:28: warning: asm output is not an lvalue
>      lib/muldi3.c:53:28: error: not addressable
>      lib/muldi3.c:53:28: warning: generating address of non-lvalue (11)
>      lib/muldi3.c:53:28: warning: generating address of non-lvalue (11)
> 
> Fix the lvalue warnings by replacing the casts on the output operands by
> intermediate variables of the right type.
> 
> Fix the "not addressable" error by replacing the cast on the second
> input operand by an intermediate variable, too.  Treat the other input
> operand the same for consistency.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202501030516.uZrwnuQQ-lkp@intel.com/
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Thanks for cleaning this up.

Acked-by: Greg Ungerer <gerg@linux-m68k.org>

Regards
Greg



> ---
> To be queued in the m68k for-v6.14 branch.
> Not folding into commit e96424b86d5098f4 ("m68k: Use kernel's generic
> muldi3 libgcc function"), as the issue was pre-existing.
> ---
>   arch/m68k/include/asm/libgcc.h | 17 ++++++++++++-----
>   1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/m68k/include/asm/libgcc.h b/arch/m68k/include/asm/libgcc.h
> index 1cce6d130d805368..27e17195bd7be41c 100644
> --- a/arch/m68k/include/asm/libgcc.h
> +++ b/arch/m68k/include/asm/libgcc.h
> @@ -10,11 +10,18 @@
>    * will fallback to using the C-coded version of umul_ppmm().
>    */
>   #define umul_ppmm(w1, w0, u, v)				\
> -	__asm__ ("mulu%.l %3,%1:%0"			\
> -		 : "=d" ((unsigned long)(w0)),		\
> -		   "=d" ((unsigned long)(w1))		\
> -		 : "%0" ((unsigned long)(u)),		\
> -		   "dmi" ((unsigned long)(v)))
> +	do {						\
> +		unsigned long __u = (u), __v = (v);	\
> +		unsigned long __w0, __w1;		\
> +							\
> +		__asm__ ("mulu%.l %3,%1:%0"		\
> +			 : "=d" (__w0),			\
> +			   "=d" (__w1)			\
> +			 : "%0" (__u),			\
> +			   "dmi" (__v));		\
> +							\
> +		(w0) = __w0; (w1) = __w1;		\
> +	} while (0)
>   #endif /* !CONFIG_CPU_HAS_NO_MULDIV64 */
>   
>   #endif /* __ASM_M68K_LIBGCC_H */