qemu

host-utils.c (12764B)

---

 /*
  * Utility compute operations used by translated code.
  *
  * Copyright (c) 2003 Fabrice Bellard
  * Copyright (c) 2007 Aurelien Jarno
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 
 #include "qemu/osdep.h"
 #include "qemu/host-utils.h"
 
 #ifndef CONFIG_INT128
 /* Long integer helpers */
 static inline void mul64(uint64_t *plow, uint64_t *phigh,
                          uint64_t a, uint64_t b)
 {
     typedef union {
         uint64_t ll;
         struct {
 #if HOST_BIG_ENDIAN
             uint32_t high, low;
 #else
             uint32_t low, high;
 #endif
         } l;
     } LL;
     LL rl, rm, rn, rh, a0, b0;
     uint64_t c;
 
     a0.ll = a;
     b0.ll = b;
 
     rl.ll = (uint64_t)a0.l.low * b0.l.low;
     rm.ll = (uint64_t)a0.l.low * b0.l.high;
     rn.ll = (uint64_t)a0.l.high * b0.l.low;
     rh.ll = (uint64_t)a0.l.high * b0.l.high;
 
     c = (uint64_t)rl.l.high + rm.l.low + rn.l.low;
     rl.l.high = c;
     c >>= 32;
     c = c + rm.l.high + rn.l.high + rh.l.low;
     rh.l.low = c;
     rh.l.high += (uint32_t)(c >> 32);
 
     *plow = rl.ll;
     *phigh = rh.ll;
 }
 
 /* Unsigned 64x64 -> 128 multiplication */
 void mulu64 (uint64_t *plow, uint64_t *phigh, uint64_t a, uint64_t b)
 {
     mul64(plow, phigh, a, b);
 }
 
 /* Signed 64x64 -> 128 multiplication */
 void muls64 (uint64_t *plow, uint64_t *phigh, int64_t a, int64_t b)
 {
     uint64_t rh;
 
     mul64(plow, &rh, a, b);
 
     /* Adjust for signs.  */
     if (b < 0) {
         rh -= a;
     }
     if (a < 0) {
         rh -= b;
     }
     *phigh = rh;
 }
 
 /*
  * Unsigned 128-by-64 division.
  * Returns the remainder.
  * Returns quotient via plow and phigh.
  * Also returns the remainder via the function return value.
  */
 uint64_t divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor)
 {
     uint64_t dhi = *phigh;
     uint64_t dlo = *plow;
     uint64_t rem, dhighest;
     int sh;
 
     if (divisor == 0 || dhi == 0) {
         *plow  = dlo / divisor;
         *phigh = 0;
         return dlo % divisor;
     } else {
         sh = clz64(divisor);
 
         if (dhi < divisor) {
             if (sh != 0) {
                 /* normalize the divisor, shifting the dividend accordingly */
                 divisor <<= sh;
                 dhi = (dhi << sh) | (dlo >> (64 - sh));
                 dlo <<= sh;
             }
 
             *phigh = 0;
             *plow = udiv_qrnnd(&rem, dhi, dlo, divisor);
         } else {
             if (sh != 0) {
                 /* normalize the divisor, shifting the dividend accordingly */
                 divisor <<= sh;
                 dhighest = dhi >> (64 - sh);
                 dhi = (dhi << sh) | (dlo >> (64 - sh));
                 dlo <<= sh;
 
                 *phigh = udiv_qrnnd(&dhi, dhighest, dhi, divisor);
             } else {
                 /**
                  * dhi >= divisor
                  * Since the MSB of divisor is set (sh == 0),
                  * (dhi - divisor) < divisor
                  *
                  * Thus, the high part of the quotient is 1, and we can
                  * calculate the low part with a single call to udiv_qrnnd
                  * after subtracting divisor from dhi
                  */
                 dhi -= divisor;
                 *phigh = 1;
             }
 
             *plow = udiv_qrnnd(&rem, dhi, dlo, divisor);
         }
 
         /*
          * since the dividend/divisor might have been normalized,
          * the remainder might also have to be shifted back
          */
         return rem >> sh;
     }
 }
 
 /*
  * Signed 128-by-64 division.
  * Returns quotient via plow and phigh.
  * Also returns the remainder via the function return value.
  */
 int64_t divs128(uint64_t *plow, int64_t *phigh, int64_t divisor)
 {
     bool neg_quotient = false, neg_remainder = false;
     uint64_t unsig_hi = *phigh, unsig_lo = *plow;
     uint64_t rem;
 
     if (*phigh < 0) {
         neg_quotient = !neg_quotient;
         neg_remainder = !neg_remainder;
 
         if (unsig_lo == 0) {
             unsig_hi = -unsig_hi;
         } else {
             unsig_hi = ~unsig_hi;
             unsig_lo = -unsig_lo;
         }
     }
 
     if (divisor < 0) {
         neg_quotient = !neg_quotient;
 
         divisor = -divisor;
     }
 
     rem = divu128(&unsig_lo, &unsig_hi, (uint64_t)divisor);
 
     if (neg_quotient) {
         if (unsig_lo == 0) {
             *phigh = -unsig_hi;
             *plow = 0;
         } else {
             *phigh = ~unsig_hi;
             *plow = -unsig_lo;
         }
     } else {
         *phigh = unsig_hi;
         *plow = unsig_lo;
     }
 
     if (neg_remainder) {
         return -rem;
     } else {
         return rem;
     }
 }
 #endif
 
 /**
  * urshift - 128-bit Unsigned Right Shift.
  * @plow: in/out - lower 64-bit integer.
  * @phigh: in/out - higher 64-bit integer.
  * @shift: in - bytes to shift, between 0 and 127.
  *
  * Result is zero-extended and stored in plow/phigh, which are
  * input/output variables. Shift values outside the range will
  * be mod to 128. In other words, the caller is responsible to
  * verify/assert both the shift range and plow/phigh pointers.
  */
 void urshift(uint64_t *plow, uint64_t *phigh, int32_t shift)
 {
     shift &= 127;
     if (shift == 0) {
         return;
     }
 
     uint64_t h = *phigh >> (shift & 63);
     if (shift >= 64) {
         *plow = h;
         *phigh = 0;
     } else {
         *plow = (*plow >> (shift & 63)) | (*phigh << (64 - (shift & 63)));
         *phigh = h;
     }
 }
 
 /**
  * ulshift - 128-bit Unsigned Left Shift.
  * @plow: in/out - lower 64-bit integer.
  * @phigh: in/out - higher 64-bit integer.
  * @shift: in - bytes to shift, between 0 and 127.
  * @overflow: out - true if any 1-bit is shifted out.
  *
  * Result is zero-extended and stored in plow/phigh, which are
  * input/output variables. Shift values outside the range will
  * be mod to 128. In other words, the caller is responsible to
  * verify/assert both the shift range and plow/phigh pointers.
  */
 void ulshift(uint64_t *plow, uint64_t *phigh, int32_t shift, bool *overflow)
 {
     uint64_t low = *plow;
     uint64_t high = *phigh;
 
     shift &= 127;
     if (shift == 0) {
         return;
     }
 
     /* check if any bit will be shifted out */
     urshift(&low, &high, 128 - shift);
     if (low | high) {
         *overflow = true;
     }
 
     if (shift >= 64) {
         *phigh = *plow << (shift & 63);
         *plow = 0;
     } else {
         *phigh = (*plow >> (64 - (shift & 63))) | (*phigh << (shift & 63));
         *plow = *plow << shift;
     }
 }
 
 /*
  * Unsigned 256-by-128 division.
  * Returns the remainder via r.
  * Returns lower 128 bit of quotient.
  * Needs a normalized divisor (most significant bit set to 1).
  *
  * Adapted from include/qemu/host-utils.h udiv_qrnnd,
  * from the GNU Multi Precision Library - longlong.h __udiv_qrnnd
  * (https://gmplib.org/repo/gmp/file/tip/longlong.h)
  *
  * Licensed under the GPLv2/LGPLv3
  */
 static Int128 udiv256_qrnnd(Int128 *r, Int128 n1, Int128 n0, Int128 d)
 {
     Int128 d0, d1, q0, q1, r1, r0, m;
     uint64_t mp0, mp1;
 
     d0 = int128_make64(int128_getlo(d));
     d1 = int128_make64(int128_gethi(d));
 
     r1 = int128_remu(n1, d1);
     q1 = int128_divu(n1, d1);
     mp0 = int128_getlo(q1);
     mp1 = int128_gethi(q1);
     mulu128(&mp0, &mp1, int128_getlo(d0));
     m = int128_make128(mp0, mp1);
     r1 = int128_make128(int128_gethi(n0), int128_getlo(r1));
     if (int128_ult(r1, m)) {
         q1 = int128_sub(q1, int128_one());
         r1 = int128_add(r1, d);
         if (int128_uge(r1, d)) {
             if (int128_ult(r1, m)) {
                 q1 = int128_sub(q1, int128_one());
                 r1 = int128_add(r1, d);
             }
         }
     }
     r1 = int128_sub(r1, m);
 
     r0 = int128_remu(r1, d1);
     q0 = int128_divu(r1, d1);
     mp0 = int128_getlo(q0);
     mp1 = int128_gethi(q0);
     mulu128(&mp0, &mp1, int128_getlo(d0));
     m = int128_make128(mp0, mp1);
     r0 = int128_make128(int128_getlo(n0), int128_getlo(r0));
     if (int128_ult(r0, m)) {
         q0 = int128_sub(q0, int128_one());
         r0 = int128_add(r0, d);
         if (int128_uge(r0, d)) {
             if (int128_ult(r0, m)) {
                 q0 = int128_sub(q0, int128_one());
                 r0 = int128_add(r0, d);
             }
         }
     }
     r0 = int128_sub(r0, m);
 
     *r = r0;
     return int128_or(int128_lshift(q1, 64), q0);
 }
 
 /*
  * Unsigned 256-by-128 division.
  * Returns the remainder.
  * Returns quotient via plow and phigh.
  * Also returns the remainder via the function return value.
  */
 Int128 divu256(Int128 *plow, Int128 *phigh, Int128 divisor)
 {
     Int128 dhi = *phigh;
     Int128 dlo = *plow;
     Int128 rem, dhighest;
     int sh;
 
     if (!int128_nz(divisor) || !int128_nz(dhi)) {
         *plow  = int128_divu(dlo, divisor);
         *phigh = int128_zero();
         return int128_remu(dlo, divisor);
     } else {
         sh = clz128(divisor);
 
         if (int128_ult(dhi, divisor)) {
             if (sh != 0) {
                 /* normalize the divisor, shifting the dividend accordingly */
                 divisor = int128_lshift(divisor, sh);
                 dhi = int128_or(int128_lshift(dhi, sh),
                                 int128_urshift(dlo, (128 - sh)));
                 dlo = int128_lshift(dlo, sh);
             }
 
             *phigh = int128_zero();
             *plow = udiv256_qrnnd(&rem, dhi, dlo, divisor);
         } else {
             if (sh != 0) {
                 /* normalize the divisor, shifting the dividend accordingly */
                 divisor = int128_lshift(divisor, sh);
                 dhighest = int128_rshift(dhi, (128 - sh));
                 dhi = int128_or(int128_lshift(dhi, sh),
                                 int128_urshift(dlo, (128 - sh)));
                 dlo = int128_lshift(dlo, sh);
 
                 *phigh = udiv256_qrnnd(&dhi, dhighest, dhi, divisor);
             } else {
                 /*
                  * dhi >= divisor
                  * Since the MSB of divisor is set (sh == 0),
                  * (dhi - divisor) < divisor
                  *
                  * Thus, the high part of the quotient is 1, and we can
                  * calculate the low part with a single call to udiv_qrnnd
                  * after subtracting divisor from dhi
                  */
                 dhi = int128_sub(dhi, divisor);
                 *phigh = int128_one();
             }
 
             *plow = udiv256_qrnnd(&rem, dhi, dlo, divisor);
         }
 
         /*
          * since the dividend/divisor might have been normalized,
          * the remainder might also have to be shifted back
          */
         rem = int128_urshift(rem, sh);
         return rem;
     }
 }
 
 /*
  * Signed 256-by-128 division.
  * Returns quotient via plow and phigh.
  * Also returns the remainder via the function return value.
  */
 Int128 divs256(Int128 *plow, Int128 *phigh, Int128 divisor)
 {
     bool neg_quotient = false, neg_remainder = false;
     Int128 unsig_hi = *phigh, unsig_lo = *plow;
     Int128 rem;
 
     if (!int128_nonneg(*phigh)) {
         neg_quotient = !neg_quotient;
         neg_remainder = !neg_remainder;
 
         if (!int128_nz(unsig_lo)) {
             unsig_hi = int128_neg(unsig_hi);
         } else {
             unsig_hi = int128_not(unsig_hi);
             unsig_lo = int128_neg(unsig_lo);
         }
     }
 
     if (!int128_nonneg(divisor)) {
         neg_quotient = !neg_quotient;
 
         divisor = int128_neg(divisor);
     }
 
     rem = divu256(&unsig_lo, &unsig_hi, divisor);
 
     if (neg_quotient) {
         if (!int128_nz(unsig_lo)) {
             *phigh = int128_neg(unsig_hi);
             *plow = int128_zero();
         } else {
             *phigh = int128_not(unsig_hi);
             *plow = int128_neg(unsig_lo);
         }
     } else {
         *phigh = unsig_hi;
         *plow = unsig_lo;
     }
 
     if (neg_remainder) {
         return int128_neg(rem);
     } else {
         return rem;
     }
 }