1218105Sjilles/* SPDX-License-Identifier: GPL-2.0 */
2218105Sjilles#ifndef _ASM_X86_DIV64_H
3218105Sjilles#define _ASM_X86_DIV64_H
4218105Sjilles
5218105Sjilles#ifdef CONFIG_X86_32
6218105Sjilles
7218105Sjilles#include <linux/types.h>
8218105Sjilles#include <linux/log2.h>
9218105Sjilles
10218105Sjilles/*
11 * do_div() is NOT a C function. It wants to return
12 * two values (the quotient and the remainder), but
13 * since that doesn't work very well in C, what it
14 * does is:
15 *
16 * - modifies the 64-bit dividend _in_place_
17 * - returns the 32-bit remainder
18 *
19 * This ends up being the most efficient "calling
20 * convention" on x86.
21 */
22#define do_div(n, base)						\
23({								\
24	unsigned long __upper, __low, __high, __mod, __base;	\
25	__base = (base);					\
26	if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \
27		__mod = n & (__base - 1);			\
28		n >>= ilog2(__base);				\
29	} else {						\
30		asm("" : "=a" (__low), "=d" (__high) : "A" (n));\
31		__upper = __high;				\
32		if (__high) {					\
33			__upper = __high % (__base);		\
34			__high = __high / (__base);		\
35		}						\
36		asm("divl %2" : "=a" (__low), "=d" (__mod)	\
37			: "rm" (__base), "0" (__low), "1" (__upper));	\
38		asm("" : "=A" (n) : "a" (__low), "d" (__high));	\
39	}							\
40	__mod;							\
41})
42
43static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
44{
45	union {
46		u64 v64;
47		u32 v32[2];
48	} d = { dividend };
49	u32 upper;
50
51	upper = d.v32[1];
52	d.v32[1] = 0;
53	if (upper >= divisor) {
54		d.v32[1] = upper / divisor;
55		upper %= divisor;
56	}
57	asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) :
58		"rm" (divisor), "0" (d.v32[0]), "1" (upper));
59	return d.v64;
60}
61#define div_u64_rem	div_u64_rem
62
63static inline u64 mul_u32_u32(u32 a, u32 b)
64{
65	u32 high, low;
66
67	asm ("mull %[b]" : "=a" (low), "=d" (high)
68			 : [a] "a" (a), [b] "rm" (b) );
69
70	return low | ((u64)high) << 32;
71}
72#define mul_u32_u32 mul_u32_u32
73
74/*
75 * __div64_32() is never called on x86, so prevent the
76 * generic definition from getting built.
77 */
78#define __div64_32
79
80#else
81# include <asm-generic/div64.h>
82
83/*
84 * Will generate an #DE when the result doesn't fit u64, could fix with an
85 * __ex_table[] entry when it becomes an issue.
86 */
87static inline u64 mul_u64_u64_div_u64(u64 a, u64 mul, u64 div)
88{
89	u64 q;
90
91	asm ("mulq %2; divq %3" : "=a" (q)
92				: "a" (a), "rm" (mul), "rm" (div)
93				: "rdx");
94
95	return q;
96}
97#define mul_u64_u64_div_u64 mul_u64_u64_div_u64
98
99static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 div)
100{
101	return mul_u64_u64_div_u64(a, mul, div);
102}
103#define mul_u64_u32_div	mul_u64_u32_div
104
105#endif /* CONFIG_X86_32 */
106
107#endif /* _ASM_X86_DIV64_H */
108