1 /* SPDX-License-Identifier: GPL-2.0 */
5 #include <linux/types.h>
6 #include <linux/limits.h>
7 #include <linux/math.h>
8 #include <linux/math64.h>
13  * u128_u: u128 user mode, because not all architectures support a real int128
26 static inline u128_u u64_to_u128(u64 a)  in u64_to_u128()  argument
28 	return (u128_u) { .v = a };  in u64_to_u128()
31 static inline u64 u128_lo(u128_u a)  in u128_lo()  argument
33 	return a.v;  in u128_lo()
36 static inline u64 u128_hi(u128_u a)  in u128_hi()  argument
38 	return a.v >> 64;  in u128_hi()
41 static inline u128_u u128_add(u128_u a, u128_u b)  in u128_add()  argument
43 	a.v += b.v;  in u128_add()
44 	return a;  in u128_add()
47 static inline u128_u u128_sub(u128_u a, u128_u b)  in u128_sub()  argument
49 	a.v -= b.v;  in u128_sub()
50 	return a;  in u128_sub()
53 static inline u128_u u128_shl(u128_u a, s8 shift)  in u128_shl()  argument
55 	a.v <<= shift;  in u128_shl()
56 	return a;  in u128_shl()
59 static inline u128_u u128_square(u64 a)  in u128_square()  argument
61 	u128_u b = u64_to_u128(a);  in u128_square()
75 static inline u128_u u64_to_u128(u64 a)  in u64_to_u128()  argument
77 	return (u128_u) { .lo = a };  in u64_to_u128()
80 static inline u64 u128_lo(u128_u a)  in u128_lo()  argument
82 	return a.lo;  in u128_lo()
85 static inline u64 u128_hi(u128_u a)  in u128_hi()  argument
87 	return a.hi;  in u128_hi()
92 static inline u128_u u128_add(u128_u a, u128_u b)  in u128_add()  argument
96 	c.lo = a.lo + b.lo;  in u128_add()
97 	c.hi = a.hi + b.hi + (c.lo < a.lo);  in u128_add()
101 static inline u128_u u128_sub(u128_u a, u128_u b)  in u128_sub()  argument
105 	c.lo = a.lo - b.lo;  in u128_sub()
106 	c.hi = a.hi - b.hi - (c.lo > a.lo);  in u128_sub()
116 		r.hi = (i.hi << (shift & 63)) | (i.lo >> (-shift & 63));  in u128_shl()
118 		r.hi = i.lo << (-shift & 63);  in u128_shl()
127 	u64  h = i >> 32, l = i & U32_MAX;  in u128_square()  local
129 	r =             u128_shl(u64_to_u128(h*h), 64);  in u128_square()
130 	r = u128_add(r, u128_shl(u64_to_u128(h*l), 32));  in u128_square()
131 	r = u128_add(r, u128_shl(u64_to_u128(l*h), 32));  in u128_square()
162  * fast_divpow2() - fast approximation for n / (1 << d)
170 	return (n + ((n < 0) ? ((1 << d) - 1) : 0)) >> d;  in fast_divpow2()
174  * mean_and_variance_update() - update a mean_and_variance struct @s1 with a new sample @v1
184 	s->n++;  in mean_and_variance_update()
185 	s->sum += v;  in mean_and_variance_update()
186 	s->sum_squares = u128_add(s->sum_squares, u128_square(abs(v)));  in mean_and_variance_update()