util/host-utils.c

   1 /*
   2  * Utility compute operations used by translated code.
   3  *
   4  * Copyright (c) 2003 Fabrice Bellard
   5  * Copyright (c) 2007 Aurelien Jarno
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 #include "qemu/osdep.h"
  27 #include "qemu/host-utils.h"
  28
  29 #ifndef CONFIG_INT128
  30 /* Long integer helpers */
  31 static inline void mul64(uint64_t *plow, uint64_t *phigh,
  32                          uint64_t a, uint64_t b)
  33 {
  34     typedef union {
  35         uint64_t ll;
  36         struct {
  37 #if HOST_BIG_ENDIAN
  38             uint32_t high, low;
  39 #else
  40             uint32_t low, high;
  41 #endif
  42         } l;
  43     } LL;
  44     LL rl, rm, rn, rh, a0, b0;
  45     uint64_t c;
  46
  47     a0.ll = a;
  48     b0.ll = b;
  49
  50     rl.ll = (uint64_t)a0.l.low * b0.l.low;
  51     rm.ll = (uint64_t)a0.l.low * b0.l.high;
  52     rn.ll = (uint64_t)a0.l.high * b0.l.low;
  53     rh.ll = (uint64_t)a0.l.high * b0.l.high;
  54
  55     c = (uint64_t)rl.l.high + rm.l.low + rn.l.low;
  56     rl.l.high = c;
  57     c >>= 32;
  58     c = c + rm.l.high + rn.l.high + rh.l.low;
  59     rh.l.low = c;
  60     rh.l.high += (uint32_t)(c >> 32);
  61
  62     *plow = rl.ll;
  63     *phigh = rh.ll;
  64 }
  65
  66 /* Unsigned 64x64 -> 128 multiplication */
  67 void mulu64 (uint64_t *plow, uint64_t *phigh, uint64_t a, uint64_t b)
  68 {
  69     mul64(plow, phigh, a, b);
  70 }
  71
  72 /* Signed 64x64 -> 128 multiplication */
  73 void muls64 (uint64_t *plow, uint64_t *phigh, int64_t a, int64_t b)
  74 {
  75     uint64_t rh;
  76
  77     mul64(plow, &rh, a, b);
  78
  79     /* Adjust for signs.  */
  80     if (b < 0) {
  81         rh -= a;
  82     }
  83     if (a < 0) {
  84         rh -= b;
  85     }
  86     *phigh = rh;
  87 }
  88
  89 /*
  90  * Unsigned 128-by-64 division.
  91  * Returns the remainder.
  92  * Returns quotient via plow and phigh.
  93  * Also returns the remainder via the function return value.
  94  */
  95 uint64_t divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor)
  96 {
  97     uint64_t dhi = *phigh;
  98     uint64_t dlo = *plow;
  99     uint64_t rem, dhighest;
 100     int sh;
 101
 102     if (divisor == 0 || dhi == 0) {
 103         *plow  = dlo / divisor;
 104         *phigh = 0;
 105         return dlo % divisor;
 106     } else {
 107         sh = clz64(divisor);
 108
 109         if (dhi < divisor) {
 110             if (sh != 0) {
 111                 /* normalize the divisor, shifting the dividend accordingly */
 112                 divisor <<= sh;
 113                 dhi = (dhi << sh) | (dlo >> (64 - sh));
 114                 dlo <<= sh;
 115             }
 116
 117             *phigh = 0;
 118             *plow = udiv_qrnnd(&rem, dhi, dlo, divisor);
 119         } else {
 120             if (sh != 0) {
 121                 /* normalize the divisor, shifting the dividend accordingly */
 122                 divisor <<= sh;
 123                 dhighest = dhi >> (64 - sh);
 124                 dhi = (dhi << sh) | (dlo >> (64 - sh));
 125                 dlo <<= sh;
 126
 127                 *phigh = udiv_qrnnd(&dhi, dhighest, dhi, divisor);
 128             } else {
 129                 /**
 130                  * dhi >= divisor
 131                  * Since the MSB of divisor is set (sh == 0),
 132                  * (dhi - divisor) < divisor
 133                  *
 134                  * Thus, the high part of the quotient is 1, and we can
 135                  * calculate the low part with a single call to udiv_qrnnd
 136                  * after subtracting divisor from dhi
 137                  */
 138                 dhi -= divisor;
 139                 *phigh = 1;
 140             }
 141
 142             *plow = udiv_qrnnd(&rem, dhi, dlo, divisor);
 143         }
 144
 145         /*
 146          * since the dividend/divisor might have been normalized,
 147          * the remainder might also have to be shifted back
 148          */
 149         return rem >> sh;
 150     }
 151 }
 152
 153 /*
 154  * Signed 128-by-64 division.
 155  * Returns quotient via plow and phigh.
 156  * Also returns the remainder via the function return value.
 157  */
 158 int64_t divs128(uint64_t *plow, int64_t *phigh, int64_t divisor)
 159 {
 160     bool neg_quotient = false, neg_remainder = false;
 161     uint64_t unsig_hi = *phigh, unsig_lo = *plow;
 162     uint64_t rem;
 163
 164     if (*phigh < 0) {
 165         neg_quotient = !neg_quotient;
 166         neg_remainder = !neg_remainder;
 167
 168         if (unsig_lo == 0) {
 169             unsig_hi = -unsig_hi;
 170         } else {
 171             unsig_hi = ~unsig_hi;
 172             unsig_lo = -unsig_lo;
 173         }
 174     }
 175
 176     if (divisor < 0) {
 177         neg_quotient = !neg_quotient;
 178
 179         divisor = -divisor;
 180     }
 181
 182     rem = divu128(&unsig_lo, &unsig_hi, (uint64_t)divisor);
 183
 184     if (neg_quotient) {
 185         if (unsig_lo == 0) {
 186             *phigh = -unsig_hi;
 187             *plow = 0;
 188         } else {
 189             *phigh = ~unsig_hi;
 190             *plow = -unsig_lo;
 191         }
 192     } else {
 193         *phigh = unsig_hi;
 194         *plow = unsig_lo;
 195     }
 196
 197     if (neg_remainder) {
 198         return -rem;
 199     } else {
 200         return rem;
 201     }
 202 }
 203 #endif
 204
 205 /**
 206  * urshift - 128-bit Unsigned Right Shift.
 207  * @plow: in/out - lower 64-bit integer.
 208  * @phigh: in/out - higher 64-bit integer.
 209  * @shift: in - bytes to shift, between 0 and 127.
 210  *
 211  * Result is zero-extended and stored in plow/phigh, which are
 212  * input/output variables. Shift values outside the range will
 213  * be mod to 128. In other words, the caller is responsible to
 214  * verify/assert both the shift range and plow/phigh pointers.
 215  */
 216 void urshift(uint64_t *plow, uint64_t *phigh, int32_t shift)
 217 {
 218     shift &= 127;
 219     if (shift == 0) {
 220         return;
 221     }
 222
 223     uint64_t h = *phigh >> (shift & 63);
 224     if (shift >= 64) {
 225         *plow = h;
 226         *phigh = 0;
 227     } else {
 228         *plow = (*plow >> (shift & 63)) | (*phigh << (64 - (shift & 63)));
 229         *phigh = h;
 230     }
 231 }
 232
 233 /**
 234  * ulshift - 128-bit Unsigned Left Shift.
 235  * @plow: in/out - lower 64-bit integer.
 236  * @phigh: in/out - higher 64-bit integer.
 237  * @shift: in - bytes to shift, between 0 and 127.
 238  * @overflow: out - true if any 1-bit is shifted out.
 239  *
 240  * Result is zero-extended and stored in plow/phigh, which are
 241  * input/output variables. Shift values outside the range will
 242  * be mod to 128. In other words, the caller is responsible to
 243  * verify/assert both the shift range and plow/phigh pointers.
 244  */
 245 void ulshift(uint64_t *plow, uint64_t *phigh, int32_t shift, bool *overflow)
 246 {
 247     uint64_t low = *plow;
 248     uint64_t high = *phigh;
 249
 250     shift &= 127;
 251     if (shift == 0) {
 252         return;
 253     }
 254
 255     /* check if any bit will be shifted out */
 256     urshift(&low, &high, 128 - shift);
 257     if (low | high) {
 258         *overflow = true;
 259     }
 260
 261     if (shift >= 64) {
 262         *phigh = *plow << (shift & 63);
 263         *plow = 0;
 264     } else {
 265         *phigh = (*plow >> (64 - (shift & 63))) | (*phigh << (shift & 63));
 266         *plow = *plow << shift;
 267     }
 268 }