sysdeps/powerpc/fpu/e_hypot.c

   1 /* Pythagorean addition using doubles
   2    Copyright (C) 2011 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 not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include "math.h"
  22 #include "math_private.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 pdnum   = 2.225073858507201e-308;
  31
  32 /* __ieee754_hypot(x,y)
  33  *
  34  * This a FP only version without any FP->INT conversion.
  35  * It is similar to default C version, making appropriates
  36  * overflow and underflows checks as well scaling when it
  37  * is needed.
  38  */
  39
  40 #ifdef _ARCH_PWR7
  41 /* POWER7 isinf and isnan optimization are fast. */
  42 # define TEST_INF_NAN(x, y)                                       \
  43    if (isinf(x) || isinf(y))                                      \
  44        return INFINITY;                                           \
  45    if (isnan(x) || isnan(y))                                      \
  46        return NAN;
  47 # else
  48 /* For POWER6 and below isinf/isnan triggers LHS and PLT calls are
  49  * costly (especially for POWER6). */
  50 # define GET_TW0_HIGH_WORD(d1,d2,i1,i2)                           \
  51  do {                                                             \
  52    ieee_double_shape_type gh_u1;                                  \
  53    ieee_double_shape_type gh_u2;                                  \
  54    gh_u1.value = (d1);                                            \
  55    gh_u2.value = (d2);                                            \
  56    (i1) = gh_u1.parts.msw;                                        \
  57    (i2) = gh_u2.parts.msw;                                        \
  58  } while (0)
  59
  60 # define TEST_INF_NAN(x, y)                                      \
  61  do {                                                            \
  62    int32_t hx, hy;                                               \
  63    GET_TW0_HIGH_WORD(x, y, hx, hy);                              \
  64    if (hy > hx) {                                                \
  65      uint32_t ht = hx; hx = hy; hy = ht;                         \
  66    }                                                             \
  67    if (hx >= 0x7ff00000) {                                       \
  68      if (hx == 0x7ff00000 || hy == 0x7ff00000)                   \
  69        return INFINITY;                                          \
  70      return NAN;                                                 \
  71    }                                                             \
  72  } while (0)
  73
  74 #endif
  75
  76
  77 double
  78 __ieee754_hypot (double x, double y)
  79 {
  80   x = fabs (x);
  81   y = fabs (y);
  82
  83   TEST_INF_NAN (x, y);
  84
  85   if (y > x)
  86     {
  87       double t = x;
  88       x = y;
  89       y = t;
  90     }
  91   if (y == 0.0 || (x / y) > two60)
  92     {
  93       return x + y;
  94     }
  95   if (x > two500)
  96     {
  97       x *= twoM600;
  98       y *= twoM600;
  99       return __ieee754_sqrt (x * x + y * y) / twoM600;
 100     }
 101   if (y < twoM500)
 102     {
 103       if (y <= pdnum)
 104         {
 105           x *= two1022;
 106           y *= two1022;
 107           return __ieee754_sqrt (x * x + y * y) / two1022;
 108         }
 109       else
 110         {
 111           x *= two600;
 112           y *= two600;
 113           return __ieee754_sqrt (x * x + y * y) / two600;
 114         }
 115     }
 116   return __ieee754_sqrt (x * x + y * y);
 117 }
 118 strong_alias (__ieee754_hypot, __hypot_finite)