lib/libc/arch/arm/gen/flt_rounds.c

   1 /*      $NetBSD: flt_rounds.c,v 1.5 2015/03/19 21:22:59 joerg Exp $     */
   2
   3 /*
   4  * Copyright (c) 1996 Mark Brinicombe
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by Mark Brinicombe
  18  *      for the NetBSD Project.
  19  * 4. The name of the author may not be used to endorse or promote products
  20  *    derived from this software without specific prior written permission
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 #include <sys/cdefs.h>
  35 #if defined(LIBC_SCCS) && !defined(lint)
  36 __RCSID("$NetBSD: flt_rounds.c,v 1.5 2015/03/19 21:22:59 joerg Exp $");
  37 #endif /* LIBC_SCCS and not lint */
  38
  39 #include "namespace.h"
  40 #include <sys/types.h>
  41 #include <ieeefp.h>
  42
  43 static const int map[] = {
  44         1,      /* round to nearest */
  45         2,      /* round to positive infinity */
  46         3,      /* round to negative infinity */
  47         0       /* round to zero */
  48 };
  49
  50 /*
  51  * Return the current FP rounding mode
  52  *
  53  * Returns:
  54  *      0 - round to zero
  55  *      1 - round to nearest
  56  *      2 - round to postive infinity
  57  *      3 - round to negative infinity
  58  *
  59  * ok all we need to do is get the current FP rounding mode
  60  * index our map table and return the appropriate value.
  61  *
  62  * HOWEVER:
  63  * The ARM FPA codes the rounding mode into the actual FP instructions
  64  * so there is no such thing as a global rounding mode.
  65  * The default is round to nearest if rounding is not explicitly specified.
  66  * FP instructions generated by GCC will not explicitly specify a rounding
  67  * mode.
  68  *
  69  * So the best we can do it to return the rounding mode FP instructions
  70  * use if rounding is not specified which is round to nearest.
  71  *
  72  * This could change in the future with new floating point emulators or
  73  * soft float FP libraries.
  74  */
  75
  76 int __flt_rounds(void);
  77
  78 int
  79 __flt_rounds(void)
  80 {
  81         return(map[fpgetround()]);
  82 }