Merge branch 'master' of git://git.denx.de/u-boot-net
[platform/kernel/u-boot.git] / include / div64.h
1 #ifndef _ASM_GENERIC_DIV64_H
2 #define _ASM_GENERIC_DIV64_H
3 /*
4  * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
5  * Based on former asm-ppc/div64.h and asm-m68knommu/div64.h
6  *
7  * Optimization for constant divisors on 32-bit machines:
8  * Copyright (C) 2006-2015 Nicolas Pitre
9  *
10  * The semantics of do_div() are:
11  *
12  * uint32_t do_div(uint64_t *n, uint32_t base)
13  * {
14  *      uint32_t remainder = *n % base;
15  *      *n = *n / base;
16  *      return remainder;
17  * }
18  *
19  * NOTE: macro parameter n is evaluated multiple times,
20  *       beware of side effects!
21  */
22
23 #include <linux/types.h>
24 #include <linux/compiler.h>
25
26 #if BITS_PER_LONG == 64
27
28 # define do_div(n,base) ({                                      \
29         uint32_t __base = (base);                               \
30         uint32_t __rem;                                         \
31         __rem = ((uint64_t)(n)) % __base;                       \
32         (n) = ((uint64_t)(n)) / __base;                         \
33         __rem;                                                  \
34  })
35
36 #elif BITS_PER_LONG == 32
37
38 #include <linux/log2.h>
39
40 /*
41  * If the divisor happens to be constant, we determine the appropriate
42  * inverse at compile time to turn the division into a few inline
43  * multiplications which ought to be much faster. And yet only if compiling
44  * with a sufficiently recent gcc version to perform proper 64-bit constant
45  * propagation.
46  *
47  * (It is unfortunate that gcc doesn't perform all this internally.)
48  */
49
50 #ifndef __div64_const32_is_OK
51 #define __div64_const32_is_OK (__GNUC__ >= 4)
52 #endif
53
54 #define __div64_const32(n, ___b)                                        \
55 ({                                                                      \
56         /*                                                              \
57          * Multiplication by reciprocal of b: n / b = n * (p / b) / p   \
58          *                                                              \
59          * We rely on the fact that most of this code gets optimized    \
60          * away at compile time due to constant propagation and only    \
61          * a few multiplication instructions should remain.             \
62          * Hence this monstrous macro (static inline doesn't always     \
63          * do the trick here).                                          \
64          */                                                             \
65         uint64_t ___res, ___x, ___t, ___m, ___n = (n);                  \
66         uint32_t ___p, ___bias;                                         \
67                                                                         \
68         /* determine MSB of b */                                        \
69         ___p = 1 << ilog2(___b);                                        \
70                                                                         \
71         /* compute m = ((p << 64) + b - 1) / b */                       \
72         ___m = (~0ULL / ___b) * ___p;                                   \
73         ___m += (((~0ULL % ___b + 1) * ___p) + ___b - 1) / ___b;        \
74                                                                         \
75         /* one less than the dividend with highest result */            \
76         ___x = ~0ULL / ___b * ___b - 1;                                 \
77                                                                         \
78         /* test our ___m with res = m * x / (p << 64) */                \
79         ___res = ((___m & 0xffffffff) * (___x & 0xffffffff)) >> 32;     \
80         ___t = ___res += (___m & 0xffffffff) * (___x >> 32);            \
81         ___res += (___x & 0xffffffff) * (___m >> 32);                   \
82         ___t = (___res < ___t) ? (1ULL << 32) : 0;                      \
83         ___res = (___res >> 32) + ___t;                                 \
84         ___res += (___m >> 32) * (___x >> 32);                          \
85         ___res /= ___p;                                                 \
86                                                                         \
87         /* Now sanitize and optimize what we've got. */                 \
88         if (~0ULL % (___b / (___b & -___b)) == 0) {                     \
89                 /* special case, can be simplified to ... */            \
90                 ___n /= (___b & -___b);                                 \
91                 ___m = ~0ULL / (___b / (___b & -___b));                 \
92                 ___p = 1;                                               \
93                 ___bias = 1;                                            \
94         } else if (___res != ___x / ___b) {                             \
95                 /*                                                      \
96                  * We can't get away without a bias to compensate       \
97                  * for bit truncation errors.  To avoid it we'd need an \
98                  * additional bit to represent m which would overflow   \
99                  * a 64-bit variable.                                   \
100                  *                                                      \
101                  * Instead we do m = p / b and n / b = (n * m + m) / p. \
102                  */                                                     \
103                 ___bias = 1;                                            \
104                 /* Compute m = (p << 64) / b */                         \
105                 ___m = (~0ULL / ___b) * ___p;                           \
106                 ___m += ((~0ULL % ___b + 1) * ___p) / ___b;             \
107         } else {                                                        \
108                 /*                                                      \
109                  * Reduce m / p, and try to clear bit 31 of m when      \
110                  * possible, otherwise that'll need extra overflow      \
111                  * handling later.                                      \
112                  */                                                     \
113                 uint32_t ___bits = -(___m & -___m);                     \
114                 ___bits |= ___m >> 32;                                  \
115                 ___bits = (~___bits) << 1;                              \
116                 /*                                                      \
117                  * If ___bits == 0 then setting bit 31 is  unavoidable. \
118                  * Simply apply the maximum possible reduction in that  \
119                  * case. Otherwise the MSB of ___bits indicates the     \
120                  * best reduction we should apply.                      \
121                  */                                                     \
122                 if (!___bits) {                                         \
123                         ___p /= (___m & -___m);                         \
124                         ___m /= (___m & -___m);                         \
125                 } else {                                                \
126                         ___p >>= ilog2(___bits);                        \
127                         ___m >>= ilog2(___bits);                        \
128                 }                                                       \
129                 /* No bias needed. */                                   \
130                 ___bias = 0;                                            \
131         }                                                               \
132                                                                         \
133         /*                                                              \
134          * Now we have a combination of 2 conditions:                   \
135          *                                                              \
136          * 1) whether or not we need to apply a bias, and               \
137          *                                                              \
138          * 2) whether or not there might be an overflow in the cross    \
139          *    product determined by (___m & ((1 << 63) | (1 << 31))).   \
140          *                                                              \
141          * Select the best way to do (m_bias + m * n) / (1 << 64).      \
142          * From now on there will be actual runtime code generated.     \
143          */                                                             \
144         ___res = __arch_xprod_64(___m, ___n, ___bias);                  \
145                                                                         \
146         ___res /= ___p;                                                 \
147 })
148
149 #ifndef __arch_xprod_64
150 /*
151  * Default C implementation for __arch_xprod_64()
152  *
153  * Prototype: uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
154  * Semantic:  retval = ((bias ? m : 0) + m * n) >> 64
155  *
156  * The product is a 128-bit value, scaled down to 64 bits.
157  * Assuming constant propagation to optimize away unused conditional code.
158  * Architectures may provide their own optimized assembly implementation.
159  */
160 static inline uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
161 {
162         uint32_t m_lo = m;
163         uint32_t m_hi = m >> 32;
164         uint32_t n_lo = n;
165         uint32_t n_hi = n >> 32;
166         uint64_t res, tmp;
167
168         if (!bias) {
169                 res = ((uint64_t)m_lo * n_lo) >> 32;
170         } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
171                 /* there can't be any overflow here */
172                 res = (m + (uint64_t)m_lo * n_lo) >> 32;
173         } else {
174                 res = m + (uint64_t)m_lo * n_lo;
175                 tmp = (res < m) ? (1ULL << 32) : 0;
176                 res = (res >> 32) + tmp;
177         }
178
179         if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
180                 /* there can't be any overflow here */
181                 res += (uint64_t)m_lo * n_hi;
182                 res += (uint64_t)m_hi * n_lo;
183                 res >>= 32;
184         } else {
185                 tmp = res += (uint64_t)m_lo * n_hi;
186                 res += (uint64_t)m_hi * n_lo;
187                 tmp = (res < tmp) ? (1ULL << 32) : 0;
188                 res = (res >> 32) + tmp;
189         }
190
191         res += (uint64_t)m_hi * n_hi;
192
193         return res;
194 }
195 #endif
196
197 #ifndef __div64_32
198 extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor);
199 #endif
200
201 /* The unnecessary pointer compare is there
202  * to check for type safety (n must be 64bit)
203  */
204 # define do_div(n,base) ({                              \
205         uint32_t __base = (base);                       \
206         uint32_t __rem;                                 \
207         (void)(((typeof((n)) *)0) == ((uint64_t *)0));  \
208         if (__builtin_constant_p(__base) &&             \
209             is_power_of_2(__base)) {                    \
210                 __rem = (n) & (__base - 1);             \
211                 (n) >>= ilog2(__base);                  \
212         } else if (__div64_const32_is_OK &&             \
213                    __builtin_constant_p(__base) &&      \
214                    __base != 0) {                       \
215                 uint32_t __res_lo, __n_lo = (n);        \
216                 (n) = __div64_const32(n, __base);       \
217                 /* the remainder can be computed with 32-bit regs */ \
218                 __res_lo = (n);                         \
219                 __rem = __n_lo - __res_lo * __base;     \
220         } else if (likely(((n) >> 32) == 0)) {          \
221                 __rem = (uint32_t)(n) % __base;         \
222                 (n) = (uint32_t)(n) / __base;           \
223         } else                                          \
224                 __rem = __div64_32(&(n), __base);       \
225         __rem;                                          \
226  })
227
228 #else /* BITS_PER_LONG == ?? */
229
230 # error do_div() does not yet support the C64
231
232 #endif /* BITS_PER_LONG */
233
234 /* Wrapper for do_div(). Doesn't modify dividend and returns
235  * the result, not remainder.
236  */
237 static inline uint64_t lldiv(uint64_t dividend, uint32_t divisor)
238 {
239         uint64_t __res = dividend;
240         do_div(__res, divisor);
241         return(__res);
242 }
243
244 #endif /* _ASM_GENERIC_DIV64_H */