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131 lines
4.4 KiB
C
131 lines
4.4 KiB
C
/* Pythagorean addition using doubles
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Copyright (C) 2011-2013 Free Software Foundation, Inc.
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This file is part of the GNU C Library
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Contributed by Adhemerval Zanella <azanella@br.ibm.com>, 2011
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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 Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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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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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, see <http://www.gnu.org/licenses/>. */
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#include <math.h>
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#include <math_private.h>
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#include <stdint.h>
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static const double two60 = 1.152921504606847e+18;
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static const double two500 = 3.2733906078961419e+150;
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static const double two600 = 4.149515568880993e+180;
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static const double two1022 = 4.49423283715579e+307;
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static const double twoM500 = 3.054936363499605e-151;
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static const double twoM600 = 2.4099198651028841e-181;
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static const double two60factor = 1.5592502418239997e+290;
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static const double pdnum = 2.225073858507201e-308;
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/* __ieee754_hypot(x,y)
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*
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* This a FP only version without any FP->INT conversion.
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* It is similar to default C version, making appropriates
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* overflow and underflows checks as well scaling when it
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* is needed.
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*/
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#ifdef _ARCH_PWR7
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/* POWER7 isinf and isnan optimization are fast. */
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# define TEST_INF_NAN(x, y) \
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if (isinf(x) || isinf(y)) \
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return INFINITY; \
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if (isnan(x) || isnan(y)) \
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return NAN;
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# else
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/* For POWER6 and below isinf/isnan triggers LHS and PLT calls are
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* costly (especially for POWER6). */
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# define GET_TW0_HIGH_WORD(d1,d2,i1,i2) \
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do { \
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ieee_double_shape_type gh_u1; \
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ieee_double_shape_type gh_u2; \
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gh_u1.value = (d1); \
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gh_u2.value = (d2); \
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(i1) = gh_u1.parts.msw & 0x7fffffff; \
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(i2) = gh_u2.parts.msw & 0x7fffffff; \
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} while (0)
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# define TEST_INF_NAN(x, y) \
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do { \
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uint32_t hx, hy; \
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GET_TW0_HIGH_WORD(x, y, hx, hy); \
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if (hy > hx) { \
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uint32_t ht = hx; hx = hy; hy = ht; \
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} \
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if (hx >= 0x7ff00000) { \
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if (hx == 0x7ff00000 || hy == 0x7ff00000) \
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return INFINITY; \
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return NAN; \
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} \
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} while (0)
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#endif
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double
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__ieee754_hypot (double x, double y)
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{
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x = fabs (x);
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y = fabs (y);
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TEST_INF_NAN (x, y);
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if (y > x)
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{
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double t = x;
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x = y;
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y = t;
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}
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if (y == 0.0)
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return x;
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/* if y is higher enough, y * 2^60 might overflow. The tests if
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y >= 1.7976931348623157e+308/2^60 (two60factor) and uses the
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appropriate check to avoid the overflow exception generation. */
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if (y > two60factor)
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{
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if ((x / y) > two60)
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return x + y;
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}
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else
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{
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if (x > (y * two60))
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return x + y;
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}
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if (x > two500)
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{
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x *= twoM600;
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y *= twoM600;
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return __ieee754_sqrt (x * x + y * y) / twoM600;
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}
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if (y < twoM500)
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{
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if (y <= pdnum)
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{
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x *= two1022;
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y *= two1022;
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return __ieee754_sqrt (x * x + y * y) / two1022;
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}
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else
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{
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x *= two600;
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y *= two600;
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return __ieee754_sqrt (x * x + y * y) / two600;
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}
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}
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return __ieee754_sqrt (x * x + y * y);
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}
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strong_alias (__ieee754_hypot, __hypot_finite)
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