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111 lines
2.5 KiB
C
111 lines
2.5 KiB
C
/* Compute remainder and a congruent to the quotient.
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Copyright (C) 1997-2023 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 <math.h>
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#include <math_private.h>
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#include <libm-alias-double.h>
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#include <stdint.h>
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static const double zero = 0.0;
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double
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__remquo (double x, double y, int *quo)
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{
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int64_t hx, hy;
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uint64_t sx, qs;
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int cquo;
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EXTRACT_WORDS64 (hx, x);
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EXTRACT_WORDS64 (hy, y);
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sx = hx & UINT64_C(0x8000000000000000);
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qs = sx ^ (hy & UINT64_C(0x8000000000000000));
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hy &= UINT64_C(0x7fffffffffffffff);
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hx &= UINT64_C(0x7fffffffffffffff);
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/* Purge off exception values. */
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if (__glibc_unlikely (hy == 0))
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return (x * y) / (x * y); /* y = 0 */
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if (__builtin_expect (hx >= UINT64_C(0x7ff0000000000000) /* x not finite */
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|| hy > UINT64_C(0x7ff0000000000000), 0))/* y is NaN */
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return (x * y) / (x * y);
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if (hy <= UINT64_C(0x7fbfffffffffffff))
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x = __ieee754_fmod (x, 8 * y); /* now x < 8y */
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if (__glibc_unlikely (hx == hy))
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{
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*quo = qs ? -1 : 1;
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return zero * x;
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}
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x = fabs (x);
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INSERT_WORDS64 (y, hy);
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cquo = 0;
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if (hy <= UINT64_C(0x7fcfffffffffffff) && x >= 4 * y)
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{
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x -= 4 * y;
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cquo += 4;
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}
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if (hy <= UINT64_C(0x7fdfffffffffffff) && x >= 2 * y)
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{
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x -= 2 * y;
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cquo += 2;
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}
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if (hy < UINT64_C(0x0020000000000000))
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{
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if (x + x > y)
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{
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x -= y;
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++cquo;
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if (x + x >= y)
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{
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x -= y;
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++cquo;
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}
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}
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}
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else
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{
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double y_half = 0.5 * y;
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if (x > y_half)
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{
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x -= y;
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++cquo;
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if (x >= y_half)
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{
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x -= y;
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++cquo;
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}
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}
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}
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*quo = qs ? -cquo : cquo;
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/* Ensure correct sign of zero result in round-downward mode. */
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if (x == 0.0)
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x = 0.0;
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if (sx)
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x = -x;
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return x;
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}
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libm_alias_double (__remquo, remquo)
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