include/linux/math64.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_MATH64_H
   3 #define _LINUX_MATH64_H
   4
   5 #include <linux/types.h>
   6 #include <asm/div64.h>
   7
   8 #if BITS_PER_LONG == 64
   9
  10 #define div64_long(x, y) div64_s64((x), (y))
  11 #define div64_ul(x, y)   div64_u64((x), (y))
  12
  13 /**
  14  * div_u64_rem - unsigned 64bit divide with 32bit divisor with remainder
  15  * @dividend: unsigned 64bit dividend
  16  * @divisor: unsigned 32bit divisor
  17  * @remainder: pointer to unsigned 32bit remainder
  18  *
  19  * Return: sets ``*remainder``, then returns dividend / divisor
  20  *
  21  * This is commonly provided by 32bit archs to provide an optimized 64bit
  22  * divide.
  23  */
  24 static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
  25 {
  26         *remainder = dividend % divisor;
  27         return dividend / divisor;
  28 }
  29
  30 /**
  31  * div_s64_rem - signed 64bit divide with 32bit divisor with remainder
  32  * @dividend: signed 64bit dividend
  33  * @divisor: signed 32bit divisor
  34  * @remainder: pointer to signed 32bit remainder
  35  *
  36  * Return: sets ``*remainder``, then returns dividend / divisor
  37  */
  38 static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
  39 {
  40         *remainder = dividend % divisor;
  41         return dividend / divisor;
  42 }
  43
  44 /**
  45  * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
  46  * @dividend: unsigned 64bit dividend
  47  * @divisor: unsigned 64bit divisor
  48  * @remainder: pointer to unsigned 64bit remainder
  49  *
  50  * Return: sets ``*remainder``, then returns dividend / divisor
  51  */
  52 static inline u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
  53 {
  54         *remainder = dividend % divisor;
  55         return dividend / divisor;
  56 }
  57
  58 /**
  59  * div64_u64 - unsigned 64bit divide with 64bit divisor
  60  * @dividend: unsigned 64bit dividend
  61  * @divisor: unsigned 64bit divisor
  62  *
  63  * Return: dividend / divisor
  64  */
  65 static inline u64 div64_u64(u64 dividend, u64 divisor)
  66 {
  67         return dividend / divisor;
  68 }
  69
  70 /**
  71  * div64_s64 - signed 64bit divide with 64bit divisor
  72  * @dividend: signed 64bit dividend
  73  * @divisor: signed 64bit divisor
  74  *
  75  * Return: dividend / divisor
  76  */
  77 static inline s64 div64_s64(s64 dividend, s64 divisor)
  78 {
  79         return dividend / divisor;
  80 }
  81
  82 #elif BITS_PER_LONG == 32
  83
  84 #define div64_long(x, y) div_s64((x), (y))
  85 #define div64_ul(x, y)   div_u64((x), (y))
  86
  87 #ifndef div_u64_rem
  88 static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
  89 {
  90         *remainder = do_div(dividend, divisor);
  91         return dividend;
  92 }
  93 #endif
  94
  95 #ifndef div_s64_rem
  96 extern s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder);
  97 #endif
  98
  99 #ifndef div64_u64_rem
 100 extern u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder);
 101 #endif
 102
 103 #ifndef div64_u64
 104 extern u64 div64_u64(u64 dividend, u64 divisor);
 105 #endif
 106
 107 #ifndef div64_s64
 108 extern s64 div64_s64(s64 dividend, s64 divisor);
 109 #endif
 110
 111 #endif /* BITS_PER_LONG */
 112
 113 /**
 114  * div_u64 - unsigned 64bit divide with 32bit divisor
 115  * @dividend: unsigned 64bit dividend
 116  * @divisor: unsigned 32bit divisor
 117  *
 118  * This is the most common 64bit divide and should be used if possible,
 119  * as many 32bit archs can optimize this variant better than a full 64bit
 120  * divide.
 121  */
 122 #ifndef div_u64
 123 static inline u64 div_u64(u64 dividend, u32 divisor)
 124 {
 125         u32 remainder;
 126         return div_u64_rem(dividend, divisor, &remainder);
 127 }
 128 #endif
 129
 130 /**
 131  * div_s64 - signed 64bit divide with 32bit divisor
 132  * @dividend: signed 64bit dividend
 133  * @divisor: signed 32bit divisor
 134  */
 135 #ifndef div_s64
 136 static inline s64 div_s64(s64 dividend, s32 divisor)
 137 {
 138         s32 remainder;
 139         return div_s64_rem(dividend, divisor, &remainder);
 140 }
 141 #endif
 142
 143 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder);
 144
 145 static __always_inline u32
 146 __iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
 147 {
 148         u32 ret = 0;
 149
 150         while (dividend >= divisor) {
 151                 /* The following asm() prevents the compiler from
 152                    optimising this loop into a modulo operation.  */
 153                 asm("" : "+rm"(dividend));
 154
 155                 dividend -= divisor;
 156                 ret++;
 157         }
 158
 159         *remainder = dividend;
 160
 161         return ret;
 162 }
 163
 164 #ifndef mul_u32_u32
 165 /*
 166  * Many a GCC version messes this up and generates a 64x64 mult :-(
 167  */
 168 static inline u64 mul_u32_u32(u32 a, u32 b)
 169 {
 170         return (u64)a * b;
 171 }
 172 #endif
 173
 174 #if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 175
 176 #ifndef mul_u64_u32_shr
 177 static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
 178 {
 179         return (u64)(((unsigned __int128)a * mul) >> shift);
 180 }
 181 #endif /* mul_u64_u32_shr */
 182
 183 #ifndef mul_u64_u64_shr
 184 static inline u64 mul_u64_u64_shr(u64 a, u64 mul, unsigned int shift)
 185 {
 186         return (u64)(((unsigned __int128)a * mul) >> shift);
 187 }
 188 #endif /* mul_u64_u64_shr */
 189
 190 #else
 191
 192 #ifndef mul_u64_u32_shr
 193 static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
 194 {
 195         u32 ah, al;
 196         u64 ret;
 197
 198         al = a;
 199         ah = a >> 32;
 200
 201         ret = mul_u32_u32(al, mul) >> shift;
 202         if (ah)
 203                 ret += mul_u32_u32(ah, mul) << (32 - shift);
 204
 205         return ret;
 206 }
 207 #endif /* mul_u64_u32_shr */
 208
 209 #ifndef mul_u64_u64_shr
 210 static inline u64 mul_u64_u64_shr(u64 a, u64 b, unsigned int shift)
 211 {
 212         union {
 213                 u64 ll;
 214                 struct {
 215 #ifdef __BIG_ENDIAN
 216                         u32 high, low;
 217 #else
 218                         u32 low, high;
 219 #endif
 220                 } l;
 221         } rl, rm, rn, rh, a0, b0;
 222         u64 c;
 223
 224         a0.ll = a;
 225         b0.ll = b;
 226
 227         rl.ll = mul_u32_u32(a0.l.low, b0.l.low);
 228         rm.ll = mul_u32_u32(a0.l.low, b0.l.high);
 229         rn.ll = mul_u32_u32(a0.l.high, b0.l.low);
 230         rh.ll = mul_u32_u32(a0.l.high, b0.l.high);
 231
 232         /*
 233          * Each of these lines computes a 64-bit intermediate result into "c",
 234          * starting at bits 32-95.  The low 32-bits go into the result of the
 235          * multiplication, the high 32-bits are carried into the next step.
 236          */
 237         rl.l.high = c = (u64)rl.l.high + rm.l.low + rn.l.low;
 238         rh.l.low = c = (c >> 32) + rm.l.high + rn.l.high + rh.l.low;
 239         rh.l.high = (c >> 32) + rh.l.high;
 240
 241         /*
 242          * The 128-bit result of the multiplication is in rl.ll and rh.ll,
 243          * shift it right and throw away the high part of the result.
 244          */
 245         if (shift == 0)
 246                 return rl.ll;
 247         if (shift < 64)
 248                 return (rl.ll >> shift) | (rh.ll << (64 - shift));
 249         return rh.ll >> (shift & 63);
 250 }
 251 #endif /* mul_u64_u64_shr */
 252
 253 #endif
 254
 255 #ifndef mul_u64_u32_div
 256 static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor)
 257 {
 258         union {
 259                 u64 ll;
 260                 struct {
 261 #ifdef __BIG_ENDIAN
 262                         u32 high, low;
 263 #else
 264                         u32 low, high;
 265 #endif
 266                 } l;
 267         } u, rl, rh;
 268
 269         u.ll = a;
 270         rl.ll = mul_u32_u32(u.l.low, mul);
 271         rh.ll = mul_u32_u32(u.l.high, mul) + rl.l.high;
 272
 273         /* Bits 32-63 of the result will be in rh.l.low. */
 274         rl.l.high = do_div(rh.ll, divisor);
 275
 276         /* Bits 0-31 of the result will be in rl.l.low. */
 277         do_div(rl.ll, divisor);
 278
 279         rl.l.high = rh.l.low;
 280         return rl.ll;
 281 }
 282 #endif /* mul_u64_u32_div */
 283
 284 #endif /* _LINUX_MATH64_H */