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

   1 /*      $NetBSD: flt_rounds.c,v 1.2 2005/06/12 05:21:25 lukem 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 1.2 2005/06/12 05:21:25 lukem Exp $");
  37 #endif /* LIBC_SCCS and not lint */
  38
  39 #include <sys/types.h>
  40 #include <ieeefp.h>
  41
  42 static const int map[] = {
  43         1,      /* round to nearest */
  44         2,      /* round to positive infinity */
  45         3,      /* round to negative infinity */
  46         0       /* round to zero */
  47 };
  48
  49 /*
  50  * Return the current FP rounding mode
  51  *
  52  * Returns:
  53  *      0 - round to zero
  54  *      1 - round to nearest
  55  *      2 - round to postive infinity
  56  *      3 - round to negative infinity
  57  *
  58  * ok all we need to do is get the current FP rounding mode
  59  * index our map table and return the appropriate value.
  60  *
  61  * HOWEVER:
  62  * The ARM FPA codes the rounding mode into the actual FP instructions
  63  * so there is no such thing as a global rounding mode.
  64  * The default is round to nearest if rounding is not explicitly specified.
  65  * FP instructions generated by GCC will not explicitly specify a rounding
  66  * mode.
  67  *
  68  * So the best we can do it to return the rounding mode FP instructions
  69  * use if rounding is not specified which is round to nearest.
  70  *
  71  * This could change in the future with new floating point emulators or
  72  * soft float FP libraries.
  73  */
  74
  75 int __flt_rounds(void);
  76
  77 int
  78 __flt_rounds()
  79 {
  80         return(map[fpgetround()]);
  81 }