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/* Pythagorean addition using floats
Copyright (C) 2011 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,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include "math.h"
#include "math_private.h"
static const float two30 = 1.0737418e09;
static const float two50 = 1.1259000e15;
static const float two60 = 1.1529221e18;
static const float two126 = 8.5070592e+37;
static const float twoM50 = 8.8817842e-16;
static const float twoM60 = 6.7762644e-21;
static const float pdnum = 1.1754939e-38;
/* __ieee754_hypotf(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 optimizations are fast. */
# define TEST_INF_NAN(x, y) \
if (isinff(x) || isinff(y)) \
return INFINITY; \
if (isnanf(x) || isnanf(y)) \
return NAN;
# else
/* For POWER6 and below isinf/isnan triggers LHS and PLT calls are
* costly (especially for POWER6). */
# define GET_TWO_FLOAT_WORD(f1,f2,i1,i2) \
do { \
ieee_float_shape_type gf_u1; \
ieee_float_shape_type gf_u2; \
gf_u1.value = (f1); \
gf_u2.value = (f2); \
(i1) = gf_u1.word; \
(i2) = gf_u2.word; \
} while (0)
# define TEST_INF_NAN(x, y) \
do { \
int32_t hx, hy; \
GET_TWO_FLOAT_WORD(x, y, hx, hy); \
if (hy > hx) { \
uint32_t ht = hx; hx = hy; hy = ht; \
} \
if (hx >= 0x7f800000) { \
if (hx == 0x7f800000 || hy == 0x7f800000) \
return INFINITY; \
return NAN; \
} \
} while (0)
#endif
float
__ieee754_hypotf (float x, float y)
{
x = fabsf (x);
y = fabsf (y);
TEST_INF_NAN (x, y);
if (y > x)
{
float t = y;
y = x;
x = t;
}
if (y == 0.0 || (x / y) > two30)
{
return x + y;
}
if (x > two50)
{
x *= twoM60;
y *= twoM60;
return sqrtf (x * x + y * y) / twoM60;
}
if (y < twoM50)
{
if (y <= pdnum)
{
x *= two126;
y *= two126;
return sqrtf (x * x + y * y) / two126;
}
else
{
x *= two60;
y *= two60;
return sqrtf (x * x + y * y) / two60;
}
}
return sqrtf (x * x + y * y);
}
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