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/* Pythagorean addition using doubles
Copyright (C) 2011-2013 Free Software Foundation, Inc.
This file is part of the GNU C Library
Contributed by Adhemerval Zanella <azanella@br.ibm.com>, 2011
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <http://www.gnu.org/licenses/>. */
#include <math.h>
#include <math_private.h>
static const double two60 = 1.152921504606847e+18;
static const double two500 = 3.2733906078961419e+150;
static const double two600 = 4.149515568880993e+180;
static const double two1022 = 4.49423283715579e+307;
static const double twoM500 = 3.054936363499605e-151;
static const double twoM600 = 2.4099198651028841e-181;
static const double two60factor = 1.5592502418239997e+290;
static const double pdnum = 2.225073858507201e-308;
/* __ieee754_hypot(x,y)
*
* This a FP only version without any FP->INT conversion.
* It is similar to default C version, making appropriates
* overflow and underflows checks as well scaling when it
* is needed.
*/
#ifdef _ARCH_PWR7
/* POWER7 isinf and isnan optimization are fast. */
# define TEST_INF_NAN(x, y) \
if (isinf(x) || isinf(y)) \
return INFINITY; \
if (isnan(x) || isnan(y)) \
return NAN;
# else
/* For POWER6 and below isinf/isnan triggers LHS and PLT calls are
* costly (especially for POWER6). */
# define GET_TW0_HIGH_WORD(d1,d2,i1,i2) \
do { \
ieee_double_shape_type gh_u1; \
ieee_double_shape_type gh_u2; \
gh_u1.value = (d1); \
gh_u2.value = (d2); \
(i1) = gh_u1.parts.msw; \
(i2) = gh_u2.parts.msw; \
} while (0)
# define TEST_INF_NAN(x, y) \
do { \
int32_t hx, hy; \
GET_TW0_HIGH_WORD(x, y, hx, hy); \
if (hy > hx) { \
uint32_t ht = hx; hx = hy; hy = ht; \
} \
if (hx >= 0x7ff00000) { \
if (hx == 0x7ff00000 || hy == 0x7ff00000) \
return INFINITY; \
return NAN; \
} \
} while (0)
#endif
double
__ieee754_hypot (double x, double y)
{
x = fabs (x);
y = fabs (y);
TEST_INF_NAN (x, y);
if (y > x)
{
double t = x;
x = y;
y = t;
}
if (y == 0.0)
return x;
/* if y is higher enough, y * 2^60 might overflow. The tests if
y >= 1.7976931348623157e+308/2^60 (two60factor) and uses the
appropriate check to avoid the overflow exception generation. */
if (y > two60factor)
{
if ((x / y) > two60)
return x + y;
}
else
{
if (x > (y * two60))
return x + y;
}
if (x > two500)
{
x *= twoM600;
y *= twoM600;
return __ieee754_sqrt (x * x + y * y) / twoM600;
}
if (y < twoM500)
{
if (y <= pdnum)
{
x *= two1022;
y *= two1022;
return __ieee754_sqrt (x * x + y * y) / two1022;
}
else
{
x *= two600;
y *= two600;
return __ieee754_sqrt (x * x + y * y) / two600;
}
}
return __ieee754_sqrt (x * x + y * y);
}
strong_alias (__ieee754_hypot, __hypot_finite)
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