Messages in this thread Patch in this message | | | Date | Tue, 03 Sep 2019 08:32:01 -0000 | From | "tip-bot2 for Peter Zijlstra" <> | Subject | [tip: x86/asm] x86/math64: Provide a sane mul_u64_u32_div() implementation for x86_64 |
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The following commit has been merged into the x86/asm branch of tip:
Commit-ID: db4e919d9a119b7c54eb5e5ac9bee5d3eb4cb859 Gitweb: https://git.kernel.org/tip/db4e919d9a119b7c54eb5e5ac9bee5d3eb4cb859 Author: Peter Zijlstra <peterz@infradead.org> AuthorDate: Wed, 28 Aug 2019 17:39:46 +02:00 Committer: Ingo Molnar <mingo@kernel.org> CommitterDate: Tue, 03 Sep 2019 08:56:14 +02:00
x86/math64: Provide a sane mul_u64_u32_div() implementation for x86_64
On x86_64 we can do a u64 * u64 -> u128 widening multiply followed by a u128 / u64 -> u64 division to implement a sane version of mul_u64_u32_div().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/include/asm/div64.h | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/arch/x86/include/asm/div64.h b/arch/x86/include/asm/div64.h index 20a4615..9b8cb50 100644 --- a/arch/x86/include/asm/div64.h +++ b/arch/x86/include/asm/div64.h @@ -73,6 +73,19 @@ static inline u64 mul_u32_u32(u32 a, u32 b) #else # include <asm-generic/div64.h> + +static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 div) +{ + u64 q; + + asm ("mulq %2; divq %3" : "=a" (q) + : "a" (a), "rm" ((u64)mul), "rm" ((u64)div) + : "rdx"); + + return q; +} +#define mul_u64_u32_div mul_u64_u32_div + #endif /* CONFIG_X86_32 */ #endif /* _ASM_X86_DIV64_H */
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