sysdeps/powerpc/fpu/e_hypot.c

   1 /* Pythagorean addition using doubles
   2    Copyright (C) 2011-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library
   4    Contributed by Adhemerval Zanella <azanella@br.ibm.com>, 2011
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If
  18    not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include <math.h>
  21 #include <math_private.h>
  22 #include <stdint.h>
  23
  24 static const double two60   = 1.152921504606847e+18;
  25 static const double two500  = 3.2733906078961419e+150;
  26 static const double two600  = 4.149515568880993e+180;
  27 static const double two1022 = 4.49423283715579e+307;
  28 static const double twoM500 = 3.054936363499605e-151;
  29 static const double twoM600 = 2.4099198651028841e-181;
  30 static const double two60factor = 1.5592502418239997e+290;
  31 static const double pdnum   = 2.225073858507201e-308;
  32
  33 /* __ieee754_hypot(x,y)
  34  *
  35  * This a FP only version without any FP->INT conversion.
  36  * It is similar to default C version, making appropriates
  37  * overflow and underflows checks as well scaling when it
  38  * is needed.
  39  */
  40
  41 #ifdef _ARCH_PWR7
  42 /* POWER7 isinf and isnan optimization are fast. */
  43 # define TEST_INF_NAN(x, y)                                       \
  44    if (isinf(x) || isinf(y))                                      \
  45        return INFINITY;                                           \
  46    if (isnan(x) || isnan(y))                                      \
  47        return NAN;
  48 # else
  49 /* For POWER6 and below isinf/isnan triggers LHS and PLT calls are
  50  * costly (especially for POWER6). */
  51 # define GET_TW0_HIGH_WORD(d1,d2,i1,i2)                           \
  52  do {                                                             \
  53    ieee_double_shape_type gh_u1;                                  \
  54    ieee_double_shape_type gh_u2;                                  \
  55    gh_u1.value = (d1);                                            \
  56    gh_u2.value = (d2);                                            \
  57    (i1) = gh_u1.parts.msw & 0x7fffffff;                           \
  58    (i2) = gh_u2.parts.msw & 0x7fffffff;                           \
  59  } while (0)
  60
  61 # define TEST_INF_NAN(x, y)                                      \
  62  do {                                                            \
  63    uint32_t hx, hy;                                              \
  64    GET_TW0_HIGH_WORD(x, y, hx, hy);                              \
  65    if (hy > hx) {                                                \
  66      uint32_t ht = hx; hx = hy; hy = ht;                         \
  67    }                                                             \
  68    if (hx >= 0x7ff00000) {                                       \
  69      if (hx == 0x7ff00000 || hy == 0x7ff00000)                   \
  70        return INFINITY;                                          \
  71      return NAN;                                                 \
  72    }                                                             \
  73  } while (0)
  74
  75 #endif
  76
  77
  78 double
  79 __ieee754_hypot (double x, double y)
  80 {
  81   x = fabs (x);
  82   y = fabs (y);
  83
  84   TEST_INF_NAN (x, y);
  85
  86   if (y > x)
  87     {
  88       double t = x;
  89       x = y;
  90       y = t;
  91     }
  92   if (y == 0.0)
  93     return x;
  94   /* if y is higher enough, y * 2^60 might overflow. The tests if
  95      y >= 1.7976931348623157e+308/2^60 (two60factor) and uses the
  96      appropriate check to avoid the overflow exception generation.  */
  97   if (y > two60factor)
  98     {
  99       if ((x / y) > two60)
 100         return x + y;
 101     }
 102   else
 103     {
 104       if (x > (y * two60))
 105         return x + y;
 106     }
 107   if (x > two500)
 108     {
 109       x *= twoM600;
 110       y *= twoM600;
 111       return __ieee754_sqrt (x * x + y * y) / twoM600;
 112     }
 113   if (y < twoM500)
 114     {
 115       if (y <= pdnum)
 116         {
 117           x *= two1022;
 118           y *= two1022;
 119           return __ieee754_sqrt (x * x + y * y) / two1022;
 120         }
 121       else
 122         {
 123           x *= two600;
 124           y *= two600;
 125           return __ieee754_sqrt (x * x + y * y) / two600;
 126         }
 127     }
 128   return __ieee754_sqrt (x * x + y * y);
 129 }
 130 strong_alias (__ieee754_hypot, __hypot_finite)