1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_DIV64_H
3 #define _ASM_X86_DIV64_H
4
5 #ifdef CONFIG_X86_32
6
7 #include <linux/types.h>
8 #include <linux/log2.h>
9
10 /*
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), "" (__low), "1" (__upper)); \
38 asm("" : "=A" (n) : "a" (__low), "d" (__high)); \
39 } \
40 __mod; \
41 })
42
43 static 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), "" (d.v32[0]), "1" (upper));
59 return d.v64;
60 }
61 #define div_u64_rem div_u64_rem
62
63 static 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 */
87 static 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
99 static 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
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