2fc83c2cd7
Add an initial math64.h similar to linux/math64.h with functions mul_u64_u64_div64() and mul_u64_u32_shr(). This isn't a direct copy of include/linux/math64.h as that doesn't define mul_u64_u64_div64(). Implementation was written by Peter Zilkstra based on linux/math64.h and div64.h[1]. The original implementation was not optimal on arm64 as __int128 division is not optimal with a call out to __udivti3, so I dropped the __int128 variant of mul_u64_u64_div64(). [1] https://lore.kernel.org/lkml/20200322101848.GF2452@worktop.programming.kicks-ass.net/ Signed-off-by: Rob Herring <robh@kernel.org> Acked-by: Jiri Olsa <jolsa@redhat.com> Acked-by: Namhyung Kim <namhyung@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Itaru Kitayama <itaru.kitayama@gmail.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> Link: http://lore.kernel.org/lkml/20210414155412.3697605-2-robh@kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
76 lines
1.2 KiB
C
76 lines
1.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_MATH64_H
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#define _LINUX_MATH64_H
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#include <linux/types.h>
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#ifdef __x86_64__
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static inline u64 mul_u64_u64_div64(u64 a, u64 b, u64 c)
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{
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u64 q;
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asm ("mulq %2; divq %3" : "=a" (q)
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: "a" (a), "rm" (b), "rm" (c)
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: "rdx");
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return q;
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}
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#define mul_u64_u64_div64 mul_u64_u64_div64
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#endif
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#ifdef __SIZEOF_INT128__
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static inline u64 mul_u64_u32_shr(u64 a, u32 b, unsigned int shift)
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{
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return (u64)(((unsigned __int128)a * b) >> shift);
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}
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#else
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#ifdef __i386__
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static inline u64 mul_u32_u32(u32 a, u32 b)
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{
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u32 high, low;
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asm ("mull %[b]" : "=a" (low), "=d" (high)
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: [a] "a" (a), [b] "rm" (b) );
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return low | ((u64)high) << 32;
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}
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#else
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static inline u64 mul_u32_u32(u32 a, u32 b)
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{
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return (u64)a * b;
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}
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#endif
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static inline u64 mul_u64_u32_shr(u64 a, u32 b, unsigned int shift)
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{
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u32 ah, al;
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u64 ret;
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al = a;
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ah = a >> 32;
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ret = mul_u32_u32(al, b) >> shift;
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if (ah)
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ret += mul_u32_u32(ah, b) << (32 - shift);
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return ret;
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}
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#endif /* __SIZEOF_INT128__ */
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#ifndef mul_u64_u64_div64
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static inline u64 mul_u64_u64_div64(u64 a, u64 b, u64 c)
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{
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u64 quot, rem;
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quot = a / c;
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rem = a % c;
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return quot * b + (rem * b) / c;
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}
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#endif
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#endif /* _LINUX_MATH64_H */
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