libsamplerate/M4/clip_mode.m4

   1 dnl @synopsis AC_C_CLIP_MODE
   2 dnl
   3 dnl Determine the clipping mode when converting float to int.
   4 dnl @version 1.0        May 17 2003
   5 dnl @author Erik de Castro Lopo <erikd AT mega-nerd DOT com>
   6 dnl
   7 dnl Permission to use, copy, modify, distribute, and sell this file for any
   8 dnl purpose is hereby granted without fee, provided that the above copyright
   9 dnl and this permission notice appear in all copies.  No representations are
  10 dnl made about the suitability of this software for any purpose.  It is
  11 dnl provided "as is" without express or implied warranty.
  12
  13
  14
  15
  16
  17
  18
  19 dnl Find the clipping mode in the following way:
  20 dnl    1) If we are not cross compiling test it.
  21 dnl    2) IF we are cross compiling, assume that clipping isn't done correctly.
  22
  23 AC_DEFUN([AC_C_CLIP_MODE],
  24 [AC_CACHE_CHECK(processor clipping capabilities,
  25         ac_cv_c_clip_type,
  26
  27 # Initialize to unknown
  28 ac_cv_c_clip_positive=unknown
  29 ac_cv_c_clip_negative=unknown
  30
  31
  32 if test $ac_cv_c_clip_positive = unknown ; then
  33         AC_TRY_RUN(
  34         [[
  35         #define _ISOC9X_SOURCE  1
  36         #define _ISOC99_SOURCE  1
  37         #define __USE_ISOC99    1
  38         #define __USE_ISOC9X    1
  39         #include <math.h>
  40         int main (void)
  41         {       double  fval ;
  42                 int k, ival ;
  43
  44                 fval = 1.0 * 0x7FFFFFFF ;
  45                 for (k = 0 ; k < 100 ; k++)
  46                 {       ival = (lrint (fval)) >> 24 ;
  47                         if (ival != 127)
  48                                 return 1 ;
  49
  50                         fval *= 1.2499999 ;
  51                         } ;
  52
  53                         return 0 ;
  54                 }
  55                 ]],
  56                 ac_cv_c_clip_positive=yes,
  57                 ac_cv_c_clip_positive=no,
  58                 ac_cv_c_clip_positive=unknown
  59                 )
  60
  61         AC_TRY_RUN(
  62         [[
  63         #define _ISOC9X_SOURCE  1
  64         #define _ISOC99_SOURCE  1
  65         #define __USE_ISOC99    1
  66         #define __USE_ISOC9X    1
  67         #include <math.h>
  68         int main (void)
  69         {       double  fval ;
  70                 int k, ival ;
  71
  72                 fval = -8.0 * 0x10000000 ;
  73                 for (k = 0 ; k < 100 ; k++)
  74                 {       ival = (lrint (fval)) >> 24 ;
  75                         if (ival != -128)
  76                                 return 1 ;
  77
  78                         fval *= 1.2499999 ;
  79                         } ;
  80
  81                         return 0 ;
  82                 }
  83                 ]],
  84                 ac_cv_c_clip_negative=yes,
  85                 ac_cv_c_clip_negative=no,
  86                 ac_cv_c_clip_negative=unknown
  87                 )
  88         fi
  89
  90 if test $ac_cv_c_clip_positive = yes ; then
  91         ac_cv_c_clip_positive=1
  92 else
  93         ac_cv_c_clip_positive=0
  94         fi
  95
  96 if test $ac_cv_c_clip_negative = yes ; then
  97         ac_cv_c_clip_negative=1
  98 else
  99         ac_cv_c_clip_negative=0
 100         fi
 101
 102 [[
 103 case "$ac_cv_c_clip_positive$ac_cv_c_clip_negative" in
 104         "00")
 105                 ac_cv_c_clip_type="none"
 106                 ;;
 107         "10")
 108                 ac_cv_c_clip_type="positive"
 109                 ;;
 110         "01")
 111                 ac_cv_c_clip_type="negative"
 112                 ;;
 113         "11")
 114                 ac_cv_c_clip_type="both"
 115                 ;;
 116         esac
 117         ]]
 118
 119 )
 120 ]
 121
 122 )# AC_C_CLIP_MODE
 123
 124