[PATCH 6.12 126/242] MIPS: Fix the GCC version check for `__multi3 workaround

Greg Kroah-Hartman
2026-04-08T18:44:44Z

From: Maciej W. Rozycki <macro@orcam.me.uk>

commit ec8bf18814915460d9c617b556bf024efef26613 upstream.

It was only GCC 10 that fixed a MIPS64r6 code generation issue with a
`__multi3' libcall inefficiently produced to perform 64-bit widening
multiplication while suitable machine instructions exist to do such a
calculation. The fix went in with GCC commit 48b2123f6336 ("re PR
target/82981 (unnecessary __multi3 call for mips64r6 linux kernel)").

Adjust our code accordingly, removing build failures such as:

mips64-linux-ld: lib/math/div64.o: in function `mul_u64_add_u64_div_u64':
div64.c:(.text+0x84): undefined reference to `__multi3'

with the GCC versions affected.

Fixes: ebabcf17bcd7 ("MIPS: Implement __multi3 for GCC7 MIPS64r6 builds")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601140146.hMLODc6v-lkp@intel.com/
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Cc: stable@vger.kernel.org # v4.15+
Reviewed-by: David Laight <david.laight.linux@gmail.com.
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/mips/lib/multi3.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/mips/lib/multi3.c
+++ b/arch/mips/lib/multi3.c
@@ -4,12 +4,12 @@
#include "libgcc.h"

/*
- * GCC 7 & older can suboptimally generate __multi3 calls for mips64r6, so for
+ * GCC 9 & older can suboptimally generate __multi3 calls for mips64r6, so for
* that specific case only we implement that intrinsic here.
*
* See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82981
*/
-#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6) && (__GNUC__ < 8)
+#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6) && (__GNUC__ < 10)

/* multiply 64-bit values, low 64-bits returned */
static inline long long notrace dmulu(long long a, long long b)
@@ -51,4 +51,4 @@ ti_type notrace __multi3(ti_type a, ti_t
}
EXPORT_SYMBOL(__multi3);

-#endif /* 64BIT && CPU_MIPSR6 && GCC7 */
+#endif /* 64BIT && CPU_MIPSR6 && GCC9 */