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343 lines
6.6 KiB
C
343 lines
6.6 KiB
C
/* 64-bit multiplication and division
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Copyright (C) 1989, 1992-2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <endian.h>
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#include <stdlib.h>
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#include <bits/wordsize.h>
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#if __WORDSIZE != 32
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#error This is for 32-bit targets only
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#endif
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typedef unsigned int UQItype __attribute__ ((mode (QI)));
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typedef int SItype __attribute__ ((mode (SI)));
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typedef unsigned int USItype __attribute__ ((mode (SI)));
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typedef int DItype __attribute__ ((mode (DI)));
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typedef unsigned int UDItype __attribute__ ((mode (DI)));
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#define Wtype SItype
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#define HWtype SItype
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#define DWtype DItype
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#define UWtype USItype
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#define UHWtype USItype
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#define UDWtype UDItype
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#define W_TYPE_SIZE 32
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#include <stdlib/longlong.h>
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#if __BYTE_ORDER == __BIG_ENDIAN
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struct DWstruct { Wtype high, low;};
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#elif __BYTE_ORDER == __LITTLE_ENDIAN
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struct DWstruct { Wtype low, high;};
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#else
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#error Unhandled endianity
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#endif
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typedef union { struct DWstruct s; DWtype ll; } DWunion;
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/* Prototypes of exported functions. */
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extern DWtype __divdi3 (DWtype u, DWtype v);
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extern DWtype __moddi3 (DWtype u, DWtype v);
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extern UDWtype __udivdi3 (UDWtype u, UDWtype v);
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extern UDWtype __umoddi3 (UDWtype u, UDWtype v);
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static UDWtype
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__udivmoddi4 (UDWtype n, UDWtype d, UDWtype *rp)
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{
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DWunion ww;
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DWunion nn, dd;
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DWunion rr;
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UWtype d0, d1, n0, n1, n2;
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UWtype q0, q1;
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UWtype b, bm;
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nn.ll = n;
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dd.ll = d;
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d0 = dd.s.low;
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d1 = dd.s.high;
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n0 = nn.s.low;
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n1 = nn.s.high;
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#if !UDIV_NEEDS_NORMALIZATION
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if (d1 == 0)
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{
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if (d0 > n1)
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{
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/* 0q = nn / 0D */
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udiv_qrnnd (q0, n0, n1, n0, d0);
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q1 = 0;
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/* Remainder in n0. */
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}
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else
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{
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/* qq = NN / 0d */
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if (d0 == 0)
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d0 = 1 / d0; /* Divide intentionally by zero. */
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udiv_qrnnd (q1, n1, 0, n1, d0);
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udiv_qrnnd (q0, n0, n1, n0, d0);
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/* Remainder in n0. */
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}
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if (rp != 0)
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{
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rr.s.low = n0;
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rr.s.high = 0;
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*rp = rr.ll;
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}
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}
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#else /* UDIV_NEEDS_NORMALIZATION */
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if (d1 == 0)
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{
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if (d0 > n1)
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{
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/* 0q = nn / 0D */
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count_leading_zeros (bm, d0);
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if (bm != 0)
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{
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/* Normalize, i.e. make the most significant bit of the
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denominator set. */
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d0 = d0 << bm;
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n1 = (n1 << bm) | (n0 >> (W_TYPE_SIZE - bm));
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n0 = n0 << bm;
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}
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udiv_qrnnd (q0, n0, n1, n0, d0);
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q1 = 0;
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/* Remainder in n0 >> bm. */
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}
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else
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{
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/* qq = NN / 0d */
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if (d0 == 0)
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d0 = 1 / d0; /* Divide intentionally by zero. */
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count_leading_zeros (bm, d0);
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if (bm == 0)
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{
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/* From (n1 >= d0) /\ (the most significant bit of d0 is set),
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conclude (the most significant bit of n1 is set) /\ (the
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leading quotient digit q1 = 1).
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This special case is necessary, not an optimization.
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(Shifts counts of W_TYPE_SIZE are undefined.) */
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n1 -= d0;
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q1 = 1;
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}
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else
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{
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/* Normalize. */
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b = W_TYPE_SIZE - bm;
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d0 = d0 << bm;
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n2 = n1 >> b;
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n1 = (n1 << bm) | (n0 >> b);
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n0 = n0 << bm;
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udiv_qrnnd (q1, n1, n2, n1, d0);
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}
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/* n1 != d0... */
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udiv_qrnnd (q0, n0, n1, n0, d0);
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/* Remainder in n0 >> bm. */
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}
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if (rp != 0)
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{
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rr.s.low = n0 >> bm;
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rr.s.high = 0;
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*rp = rr.ll;
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}
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}
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#endif /* UDIV_NEEDS_NORMALIZATION */
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else
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{
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if (d1 > n1)
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{
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/* 00 = nn / DD */
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q0 = 0;
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q1 = 0;
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/* Remainder in n1n0. */
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if (rp != 0)
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{
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rr.s.low = n0;
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rr.s.high = n1;
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*rp = rr.ll;
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}
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}
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else
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{
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/* 0q = NN / dd */
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count_leading_zeros (bm, d1);
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if (bm == 0)
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{
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/* From (n1 >= d1) /\ (the most significant bit of d1 is set),
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conclude (the most significant bit of n1 is set) /\ (the
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quotient digit q0 = 0 or 1).
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This special case is necessary, not an optimization. */
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/* The condition on the next line takes advantage of that
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n1 >= d1 (true due to program flow). */
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if (n1 > d1 || n0 >= d0)
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{
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q0 = 1;
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sub_ddmmss (n1, n0, n1, n0, d1, d0);
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}
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else
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q0 = 0;
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q1 = 0;
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if (rp != 0)
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{
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rr.s.low = n0;
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rr.s.high = n1;
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*rp = rr.ll;
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}
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}
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else
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{
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UWtype m1, m0;
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/* Normalize. */
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b = W_TYPE_SIZE - bm;
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d1 = (d1 << bm) | (d0 >> b);
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d0 = d0 << bm;
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n2 = n1 >> b;
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n1 = (n1 << bm) | (n0 >> b);
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n0 = n0 << bm;
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udiv_qrnnd (q0, n1, n2, n1, d1);
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umul_ppmm (m1, m0, q0, d0);
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if (m1 > n1 || (m1 == n1 && m0 > n0))
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{
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q0--;
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sub_ddmmss (m1, m0, m1, m0, d1, d0);
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}
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q1 = 0;
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/* Remainder in (n1n0 - m1m0) >> bm. */
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if (rp != 0)
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{
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sub_ddmmss (n1, n0, n1, n0, m1, m0);
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rr.s.low = (n1 << b) | (n0 >> bm);
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rr.s.high = n1 >> bm;
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*rp = rr.ll;
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}
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}
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}
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}
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ww.s.low = q0;
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ww.s.high = q1;
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return ww.ll;
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}
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DWtype
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__divdi3 (DWtype u, DWtype v)
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{
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Wtype c = 0;
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DWtype w;
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if (u < 0)
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{
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c = ~c;
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u = -u;
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}
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if (v < 0)
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{
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c = ~c;
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v = -v;
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}
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w = __udivmoddi4 (u, v, NULL);
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if (c)
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w = -w;
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return w;
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}
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strong_alias (__divdi3, __divdi3_internal)
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DWtype
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__moddi3 (DWtype u, DWtype v)
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{
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Wtype c = 0;
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DWtype w;
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if (u < 0)
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{
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c = ~c;
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u = -u;
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}
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if (v < 0)
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v = -v;
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__udivmoddi4 (u, v, (UDWtype *) &w);
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if (c)
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w = -w;
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return w;
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}
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strong_alias (__moddi3, __moddi3_internal)
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UDWtype
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__udivdi3 (UDWtype u, UDWtype v)
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{
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return __udivmoddi4 (u, v, NULL);
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}
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strong_alias (__udivdi3, __udivdi3_internal)
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UDWtype
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__umoddi3 (UDWtype u, UDWtype v)
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{
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UDWtype w;
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__udivmoddi4 (u, v, &w);
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return w;
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}
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strong_alias (__umoddi3, __umoddi3_internal)
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/* We declare these with compat_symbol so that they are not visible at
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link time. Programs must use the functions from libgcc. */
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#ifdef SHARED
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# include <shlib-compat.h>
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compat_symbol (libc, __divdi3, __divdi3, GLIBC_2_0);
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compat_symbol (libc, __moddi3, __moddi3, GLIBC_2_0);
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compat_symbol (libc, __udivdi3, __udivdi3, GLIBC_2_0);
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compat_symbol (libc, __umoddi3, __umoddi3, GLIBC_2_0);
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#endif
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