* Re: [PATCH] compiler_types: Introduce inline_for_performance
[not found] <20260118152448.2560414-1-edumazet@google.com>
@ 2026-01-18 18:36 ` kernel test robot
2026-01-18 22:33 ` David Laight
2026-01-18 21:04 ` kernel test robot
1 sibling, 1 reply; 3+ messages in thread
From: kernel test robot @ 2026-01-18 18:36 UTC (permalink / raw)
To: Eric Dumazet, Andrew Morton
Cc: oe-kbuild-all, Linux Memory Management List, linux-kernel,
netdev, Jakub Kicinski, Eric Dumazet, Paolo Abeni, Nicolas Pitre
Hi Eric,
kernel test robot noticed the following build warnings:
[auto build test WARNING on e84d960149e71e8d5e4db69775ce31305898ed0c]
url: https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/compiler_types-Introduce-inline_for_performance/20260118-232653
base: e84d960149e71e8d5e4db69775ce31305898ed0c
patch link: https://lore.kernel.org/r/20260118152448.2560414-1-edumazet%40google.com
patch subject: [PATCH] compiler_types: Introduce inline_for_performance
config: m68k-amcore_defconfig (https://download.01.org/0day-ci/archive/20260119/202601190247.dDAvbbMH-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260119/202601190247.dDAvbbMH-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601190247.dDAvbbMH-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from arch/m68k/include/asm/div64.h:6,
from include/linux/math.h:6,
from include/linux/kernel.h:27,
from arch/m68k/coldfire/cache.c:12:
>> include/asm-generic/div64.h:138:10: warning: '__arch_xprod_64' defined but not used [-Wunused-function]
138 | uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
| ^~~~~~~~~~~~~~~
vim +/__arch_xprod_64 +138 include/asm-generic/div64.h
461a5e51060c93 Nicolas Pitre 2015-10-30 125
f682b27c57aec2 Nicolas Pitre 2015-10-30 126 #ifndef __arch_xprod_64
f682b27c57aec2 Nicolas Pitre 2015-10-30 127 /*
f682b27c57aec2 Nicolas Pitre 2015-10-30 128 * Default C implementation for __arch_xprod_64()
f682b27c57aec2 Nicolas Pitre 2015-10-30 129 *
f682b27c57aec2 Nicolas Pitre 2015-10-30 130 * Prototype: uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
f682b27c57aec2 Nicolas Pitre 2015-10-30 131 * Semantic: retval = ((bias ? m : 0) + m * n) >> 64
f682b27c57aec2 Nicolas Pitre 2015-10-30 132 *
f682b27c57aec2 Nicolas Pitre 2015-10-30 133 * The product is a 128-bit value, scaled down to 64 bits.
00a31dd3acea0f Nicolas Pitre 2024-10-03 134 * Hoping for compile-time optimization of conditional code.
f682b27c57aec2 Nicolas Pitre 2015-10-30 135 * Architectures may provide their own optimized assembly implementation.
f682b27c57aec2 Nicolas Pitre 2015-10-30 136 */
5f712d70e20a46 Eric Dumazet 2026-01-18 137 static inline_for_performance
d533cb2d2af400 Nicolas Pitre 2024-10-03 @138 uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
f682b27c57aec2 Nicolas Pitre 2015-10-30 139 {
f682b27c57aec2 Nicolas Pitre 2015-10-30 140 uint32_t m_lo = m;
f682b27c57aec2 Nicolas Pitre 2015-10-30 141 uint32_t m_hi = m >> 32;
f682b27c57aec2 Nicolas Pitre 2015-10-30 142 uint32_t n_lo = n;
f682b27c57aec2 Nicolas Pitre 2015-10-30 143 uint32_t n_hi = n >> 32;
00a31dd3acea0f Nicolas Pitre 2024-10-03 144 uint64_t x, y;
f682b27c57aec2 Nicolas Pitre 2015-10-30 145
00a31dd3acea0f Nicolas Pitre 2024-10-03 146 /* Determine if overflow handling can be dispensed with. */
00a31dd3acea0f Nicolas Pitre 2024-10-03 147 bool no_ovf = __builtin_constant_p(m) &&
00a31dd3acea0f Nicolas Pitre 2024-10-03 148 ((m >> 32) + (m & 0xffffffff) < 0x100000000);
f682b27c57aec2 Nicolas Pitre 2015-10-30 149
00a31dd3acea0f Nicolas Pitre 2024-10-03 150 if (no_ovf) {
00a31dd3acea0f Nicolas Pitre 2024-10-03 151 x = (uint64_t)m_lo * n_lo + (bias ? m : 0);
00a31dd3acea0f Nicolas Pitre 2024-10-03 152 x >>= 32;
00a31dd3acea0f Nicolas Pitre 2024-10-03 153 x += (uint64_t)m_lo * n_hi;
00a31dd3acea0f Nicolas Pitre 2024-10-03 154 x += (uint64_t)m_hi * n_lo;
00a31dd3acea0f Nicolas Pitre 2024-10-03 155 x >>= 32;
00a31dd3acea0f Nicolas Pitre 2024-10-03 156 x += (uint64_t)m_hi * n_hi;
f682b27c57aec2 Nicolas Pitre 2015-10-30 157 } else {
00a31dd3acea0f Nicolas Pitre 2024-10-03 158 x = (uint64_t)m_lo * n_lo + (bias ? m_lo : 0);
00a31dd3acea0f Nicolas Pitre 2024-10-03 159 y = (uint64_t)m_lo * n_hi + (uint32_t)(x >> 32) + (bias ? m_hi : 0);
00a31dd3acea0f Nicolas Pitre 2024-10-03 160 x = (uint64_t)m_hi * n_hi + (uint32_t)(y >> 32);
00a31dd3acea0f Nicolas Pitre 2024-10-03 161 y = (uint64_t)m_hi * n_lo + (uint32_t)y;
00a31dd3acea0f Nicolas Pitre 2024-10-03 162 x += (uint32_t)(y >> 32);
f682b27c57aec2 Nicolas Pitre 2015-10-30 163 }
f682b27c57aec2 Nicolas Pitre 2015-10-30 164
00a31dd3acea0f Nicolas Pitre 2024-10-03 165 return x;
f682b27c57aec2 Nicolas Pitre 2015-10-30 166 }
f682b27c57aec2 Nicolas Pitre 2015-10-30 167 #endif
f682b27c57aec2 Nicolas Pitre 2015-10-30 168
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] compiler_types: Introduce inline_for_performance
[not found] <20260118152448.2560414-1-edumazet@google.com>
2026-01-18 18:36 ` [PATCH] compiler_types: Introduce inline_for_performance kernel test robot
@ 2026-01-18 21:04 ` kernel test robot
1 sibling, 0 replies; 3+ messages in thread
From: kernel test robot @ 2026-01-18 21:04 UTC (permalink / raw)
To: Eric Dumazet, Andrew Morton
Cc: oe-kbuild-all, Linux Memory Management List, linux-kernel,
netdev, Jakub Kicinski, Eric Dumazet, Paolo Abeni, Nicolas Pitre
Hi Eric,
kernel test robot noticed the following build warnings:
[auto build test WARNING on e84d960149e71e8d5e4db69775ce31305898ed0c]
url: https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/compiler_types-Introduce-inline_for_performance/20260118-232653
base: e84d960149e71e8d5e4db69775ce31305898ed0c
patch link: https://lore.kernel.org/r/20260118152448.2560414-1-edumazet%40google.com
patch subject: [PATCH] compiler_types: Introduce inline_for_performance
config: arm-randconfig-004-20260119 (https://download.01.org/0day-ci/archive/20260119/202601190420.RlBoZSGm-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 14.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260119/202601190420.RlBoZSGm-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601190420.RlBoZSGm-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from include/linux/math.h:6,
from include/linux/kernel.h:27,
from include/linux/random.h:7,
from include/linux/nodemask.h:94,
from include/linux/numa.h:6,
from include/linux/cpumask.h:15,
from include/linux/smp.h:13,
from include/linux/lockdep.h:14,
from include/linux/spinlock.h:63,
from lib/dec_and_lock.c:3:
>> arch/arm/include/asm/div64.h:56:10: warning: '__arch_xprod_64' defined but not used [-Wunused-function]
56 | uint64_t __arch_xprod_64(uint64_t m, uint64_t n, bool bias)
| ^~~~~~~~~~~~~~~
vim +/__arch_xprod_64 +56 arch/arm/include/asm/div64.h
fa4adc614922c2 include/asm-arm/div64.h Nicolas Pitre 2006-12-06 54
5f712d70e20a46 arch/arm/include/asm/div64.h Eric Dumazet 2026-01-18 55 static inline_for_performance
d533cb2d2af400 arch/arm/include/asm/div64.h Nicolas Pitre 2024-10-03 @56 uint64_t __arch_xprod_64(uint64_t m, uint64_t n, bool bias)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 57 {
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 58 unsigned long long res;
73e592f3bc2cdc arch/arm/include/asm/div64.h Nicolas Pitre 2016-01-27 59 register unsigned int tmp asm("ip") = 0;
06508533d51a1d arch/arm/include/asm/div64.h Nicolas Pitre 2024-10-03 60 bool no_ovf = __builtin_constant_p(m) &&
06508533d51a1d arch/arm/include/asm/div64.h Nicolas Pitre 2024-10-03 61 ((m >> 32) + (m & 0xffffffff) < 0x100000000);
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 62
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 63 if (!bias) {
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 64 asm ( "umull %Q0, %R0, %Q1, %Q2\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 65 "mov %Q0, #0"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 66 : "=&r" (res)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 67 : "r" (m), "r" (n)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 68 : "cc");
06508533d51a1d arch/arm/include/asm/div64.h Nicolas Pitre 2024-10-03 69 } else if (no_ovf) {
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 70 res = m;
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 71 asm ( "umlal %Q0, %R0, %Q1, %Q2\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 72 "mov %Q0, #0"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 73 : "+&r" (res)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 74 : "r" (m), "r" (n)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 75 : "cc");
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 76 } else {
73e592f3bc2cdc arch/arm/include/asm/div64.h Nicolas Pitre 2016-01-27 77 asm ( "umull %Q0, %R0, %Q2, %Q3\n\t"
73e592f3bc2cdc arch/arm/include/asm/div64.h Nicolas Pitre 2016-01-27 78 "cmn %Q0, %Q2\n\t"
73e592f3bc2cdc arch/arm/include/asm/div64.h Nicolas Pitre 2016-01-27 79 "adcs %R0, %R0, %R2\n\t"
73e592f3bc2cdc arch/arm/include/asm/div64.h Nicolas Pitre 2016-01-27 80 "adc %Q0, %1, #0"
73e592f3bc2cdc arch/arm/include/asm/div64.h Nicolas Pitre 2016-01-27 81 : "=&r" (res), "+&r" (tmp)
73e592f3bc2cdc arch/arm/include/asm/div64.h Nicolas Pitre 2016-01-27 82 : "r" (m), "r" (n)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 83 : "cc");
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 84 }
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 85
06508533d51a1d arch/arm/include/asm/div64.h Nicolas Pitre 2024-10-03 86 if (no_ovf) {
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 87 asm ( "umlal %R0, %Q0, %R1, %Q2\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 88 "umlal %R0, %Q0, %Q1, %R2\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 89 "mov %R0, #0\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 90 "umlal %Q0, %R0, %R1, %R2"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 91 : "+&r" (res)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 92 : "r" (m), "r" (n)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 93 : "cc");
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 94 } else {
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 95 asm ( "umlal %R0, %Q0, %R2, %Q3\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 96 "umlal %R0, %1, %Q2, %R3\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 97 "mov %R0, #0\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 98 "adds %Q0, %1, %Q0\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 99 "adc %R0, %R0, #0\n\t"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 100 "umlal %Q0, %R0, %R2, %R3"
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 101 : "+&r" (res), "+&r" (tmp)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 102 : "r" (m), "r" (n)
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 103 : "cc");
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 104 }
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 105
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 106 return res;
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 107 }
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 108 #define __arch_xprod_64 __arch_xprod_64
040b323b5012b5 arch/arm/include/asm/div64.h Nicolas Pitre 2015-11-02 109
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] compiler_types: Introduce inline_for_performance
2026-01-18 18:36 ` [PATCH] compiler_types: Introduce inline_for_performance kernel test robot
@ 2026-01-18 22:33 ` David Laight
0 siblings, 0 replies; 3+ messages in thread
From: David Laight @ 2026-01-18 22:33 UTC (permalink / raw)
To: kernel test robot
Cc: Eric Dumazet, Andrew Morton, oe-kbuild-all,
Linux Memory Management List, linux-kernel, netdev,
Jakub Kicinski, Eric Dumazet, Paolo Abeni, Nicolas Pitre
On Mon, 19 Jan 2026 02:36:18 +0800
kernel test robot <lkp@intel.com> wrote:
> Hi Eric,
...
> vim +/__arch_xprod_64 +138 include/asm-generic/div64.h
>
> 461a5e51060c93 Nicolas Pitre 2015-10-30 125
> f682b27c57aec2 Nicolas Pitre 2015-10-30 126 #ifndef __arch_xprod_64
> f682b27c57aec2 Nicolas Pitre 2015-10-30 127 /*
> f682b27c57aec2 Nicolas Pitre 2015-10-30 128 * Default C implementation for __arch_xprod_64()
> f682b27c57aec2 Nicolas Pitre 2015-10-30 129 *
> f682b27c57aec2 Nicolas Pitre 2015-10-30 130 * Prototype: uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
> f682b27c57aec2 Nicolas Pitre 2015-10-30 131 * Semantic: retval = ((bias ? m : 0) + m * n) >> 64
> f682b27c57aec2 Nicolas Pitre 2015-10-30 132 *
> f682b27c57aec2 Nicolas Pitre 2015-10-30 133 * The product is a 128-bit value, scaled down to 64 bits.
> 00a31dd3acea0f Nicolas Pitre 2024-10-03 134 * Hoping for compile-time optimization of conditional code.
> f682b27c57aec2 Nicolas Pitre 2015-10-30 135 * Architectures may provide their own optimized assembly implementation.
> f682b27c57aec2 Nicolas Pitre 2015-10-30 136 */
> 5f712d70e20a46 Eric Dumazet 2026-01-18 137 static inline_for_performance
> d533cb2d2af400 Nicolas Pitre 2024-10-03 @138 uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
> f682b27c57aec2 Nicolas Pitre 2015-10-30 139 {
> f682b27c57aec2 Nicolas Pitre 2015-10-30 140 uint32_t m_lo = m;
> f682b27c57aec2 Nicolas Pitre 2015-10-30 141 uint32_t m_hi = m >> 32;
> f682b27c57aec2 Nicolas Pitre 2015-10-30 142 uint32_t n_lo = n;
> f682b27c57aec2 Nicolas Pitre 2015-10-30 143 uint32_t n_hi = n >> 32;
> 00a31dd3acea0f Nicolas Pitre 2024-10-03 144 uint64_t x, y;
> f682b27c57aec2 Nicolas Pitre 2015-10-30 145
> 00a31dd3acea0f Nicolas Pitre 2024-10-03 146 /* Determine if overflow handling can be dispensed with. */
> 00a31dd3acea0f Nicolas Pitre 2024-10-03 147 bool no_ovf = __builtin_constant_p(m) &&
> 00a31dd3acea0f Nicolas Pitre 2024-10-03 148 ((m >> 32) + (m & 0xffffffff) < 0x100000000);
Can that ever have got compiled?
Won't the compiler complain about 0x100000000 being out of range?
Lots of alternatives...
If u128 exists this should probably just be:
return ((u128)m * n + (bias ? m : 0)) >> 64;
Which is probably the only alternative an architecture might provide (none do AFAICT).
David
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-01-18 18:36 ` [PATCH] compiler_types: Introduce inline_for_performance kernel test robot
2026-01-18 22:33 ` David Laight
2026-01-18 21:04 ` kernel test robot
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