usr/src/lib/libm/common/m9x/llroundf.c

   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 #pragma weak __llroundf = llroundf
  31 #if defined(__sparcv9) || defined(__amd64)
  32 #pragma weak lroundf = llroundf
  33 #pragma weak __lroundf = llroundf
  34 #endif
  35
  36 #include "libm.h"
  37
  38 long long
  39 llroundf(float x) {
  40         union {
  41                 unsigned i;
  42                 float f;
  43         } xx;
  44         unsigned hx, sx, i;
  45
  46         xx.f = x;
  47         hx = xx.i & ~0x80000000;
  48         sx = xx.i & 0x80000000;
  49
  50         if (hx < 0x4b000000) { /* |x| < 2^23 */
  51                 /* handle |x| < 1 */
  52                 if (hx < 0x3f800000) {
  53                         if (hx >= 0x3f000000)
  54                                 return (sx ? -1LL : 1LL);
  55                         return (0LL);
  56                 }
  57
  58                 /* round x at the integer bit */
  59                 i = 1 << (0x95 - (hx >> 23));
  60                 xx.i = (xx.i + i) & ~((i << 1) - 1);
  61
  62                 /*
  63                  * on LP32 architectures, we can just convert x to a 32-bit
  64                  * integer and sign-extend it
  65                  */
  66                 return ((long) xx.f);
  67         }
  68
  69         /* now x is nan, inf, or integral */
  70         return ((long long) x);
  71 }