1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 /*
  26  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27  * Use is subject to license terms.
  28  */
  29 
  30 #if defined(ELFOBJ)
  31 #pragma weak fmax = __fmax
  32 #endif
  33 
  34 /*
  35  * fmax(x,y) returns the larger of x and y.  If just one of the
  36  * arguments is NaN, fmax returns the other argument.  If both
  37  * arguments are NaN, fmax returns NaN.
  38  *
  39  * See fmaxf.c for a discussion of implementation trade-offs.
  40  */
  41 
  42 #include "libm.h"       /* for isgreaterequal macro */
  43 #include <fenv.h>
  44 
  45 double
  46 __fmax(double x, double y) {
  47         union {
  48                 unsigned i[2];
  49                 double d;
  50         } xx, yy;
  51         unsigned s;
  52 
  53         /* if y is nan, replace it by x */
  54         if (y != y)
  55                 y = x;
  56 
  57         /* if x is nan, replace it by y */
  58         if (x != x)
  59                 x = y;
  60 
  61         /* if x is less than y or x and y are unordered, replace x by y */
  62 #if defined(COMPARISON_MACRO_BUG)
  63         if (x < y)
  64 #else
  65         if (!isgreaterequal(x, y))
  66 #endif
  67                 x = y;
  68 
  69         /*
  70          * now x and y are either both NaN or both numeric; clear the
  71          * sign of the result if either x or y has its sign clear
  72          */
  73         xx.d = x;
  74         yy.d = y;
  75 #if defined(__sparc)
  76         s = ~(xx.i[0] & yy.i[0]) & 0x80000000;
  77         xx.i[0] &= ~s;
  78 #elif defined(__x86)
  79         s = ~(xx.i[1] & yy.i[1]) & 0x80000000;
  80         xx.i[1] &= ~s;
  81 #else
  82 #error Unknown architecture
  83 #endif
  84 
  85         return (xx.d);
  86 }