While working on mul_u64_u64_div_u64() improvements I realized that there is a better way to perform a 64x64->128 bits multiplication with overflow handling. This is not as lean as v1 of the series but still much better than the existing code IMHO. Changes from v1: - Formalize condition for when overflow handling can be skipped. - Make this condition apply only if it can be determined at compile time (beware of the compiler not always inling code). - Keep the ARM assembly but apply the above changes to it as well. - Simplify generic C code for __arch_xprod64() further. - Force __always_inline when optimizing for performance. - Augment test_div64.c with important edge cases. Link to v1: https://lore.kernel.org/lkml/20240705022334.1378363-1-nico@xxxxxxxxxxx/ The diffstat is: arch/arm/include/asm/div64.h | 13 +++- include/asm-generic/div64.h | 121 ++++++++++++----------------------- lib/math/test_div64.c | 85 +++++++++++++++++++++++- 3 files changed, 134 insertions(+), 85 deletions(-)
