m4/signbit.m4

   1 # signbit.m4 serial 13
   2 dnl Copyright (C) 2007-2014 Free Software Foundation, Inc.
   3 dnl This file is free software; the Free Software Foundation
   4 dnl gives unlimited permission to copy and/or distribute it,
   5 dnl with or without modifications, as long as this notice is preserved.
   6
   7 AC_DEFUN([gl_SIGNBIT],
   8 [
   9   AC_REQUIRE([gl_MATH_H_DEFAULTS])
  10   AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  11   AC_CACHE_CHECK([for signbit macro], [gl_cv_func_signbit],
  12     [
  13       AC_RUN_IFELSE(
  14         [AC_LANG_SOURCE([[
  15 #include <math.h>
  16 /* If signbit is defined as a function, don't use it, since calling it for
  17    'float' or 'long double' arguments would involve conversions.
  18    If signbit is not declared at all but exists as a library function, don't
  19    use it, since the prototype may not match.
  20    If signbit is not declared at all but exists as a compiler built-in, don't
  21    use it, since it's preferable to use __builtin_signbit* (no warnings,
  22    no conversions).  */
  23 #ifndef signbit
  24 # error "signbit should be a macro"
  25 #endif
  26 #include <string.h>
  27 ]gl_SIGNBIT_TEST_PROGRAM
  28 ])],
  29         [gl_cv_func_signbit=yes],
  30         [gl_cv_func_signbit=no],
  31         [case "$host_os" in
  32                    # Guess yes on glibc systems.
  33            *-gnu*) gl_cv_func_signbit="guessing yes" ;;
  34                    # If we don't know, assume the worst.
  35            *)      gl_cv_func_signbit="guessing no" ;;
  36          esac
  37         ])
  38     ])
  39   dnl GCC 4.0 and newer provides three built-ins for signbit.
  40   dnl They can be used without warnings, also in C++, regardless of <math.h>.
  41   dnl But they may expand to calls to functions, which may or may not be in
  42   dnl libc.
  43   AC_CACHE_CHECK([for signbit compiler built-ins], [gl_cv_func_signbit_gcc],
  44     [
  45       AC_RUN_IFELSE(
  46         [AC_LANG_SOURCE([[
  47 #if __GNUC__ >= 4
  48 # define signbit(x) \
  49    (sizeof (x) == sizeof (long double) ? __builtin_signbitl (x) : \
  50     sizeof (x) == sizeof (double) ? __builtin_signbit (x) : \
  51     __builtin_signbitf (x))
  52 #else
  53 # error "signbit should be three compiler built-ins"
  54 #endif
  55 #include <string.h>
  56 ]gl_SIGNBIT_TEST_PROGRAM
  57 ])],
  58         [gl_cv_func_signbit_gcc=yes],
  59         [gl_cv_func_signbit_gcc=no],
  60         [case "$host_os" in
  61                    # Guess yes on glibc systems.
  62            *-gnu*) gl_cv_func_signbit_gcc="guessing yes" ;;
  63                    # If we don't know, assume the worst.
  64            *)      gl_cv_func_signbit_gcc="guessing no" ;;
  65          esac
  66         ])
  67     ])
  68   dnl Use the compiler built-ins whenever possible, because they are more
  69   dnl efficient than the system library functions (if they exist).
  70   case "$gl_cv_func_signbit_gcc" in
  71     *yes)
  72       REPLACE_SIGNBIT_USING_GCC=1
  73       ;;
  74     *)
  75       case "$gl_cv_func_signbit" in
  76         *yes) ;;
  77         *)
  78           dnl REPLACE_SIGNBIT=1 makes sure the signbit[fdl] functions get built.
  79           REPLACE_SIGNBIT=1
  80           gl_FLOAT_SIGN_LOCATION
  81           gl_DOUBLE_SIGN_LOCATION
  82           gl_LONG_DOUBLE_SIGN_LOCATION
  83           if test "$gl_cv_cc_float_signbit" = unknown; then
  84             dnl Test whether copysignf() is declared.
  85             AC_CHECK_DECLS([copysignf], , , [[#include <math.h>]])
  86             if test "$ac_cv_have_decl_copysignf" = yes; then
  87               dnl Test whether copysignf() can be used without libm.
  88               AC_CACHE_CHECK([whether copysignf can be used without linking with libm],
  89                 [gl_cv_func_copysignf_no_libm],
  90                 [
  91                   AC_LINK_IFELSE(
  92                     [AC_LANG_PROGRAM(
  93                        [[#include <math.h>
  94                          float x, y;]],
  95                        [[return copysignf (x, y) < 0;]])],
  96                     [gl_cv_func_copysignf_no_libm=yes],
  97                     [gl_cv_func_copysignf_no_libm=no])
  98                 ])
  99               if test $gl_cv_func_copysignf_no_libm = yes; then
 100                 AC_DEFINE([HAVE_COPYSIGNF_IN_LIBC], [1],
 101                   [Define if the copysignf function is declared in <math.h> and available in libc.])
 102               fi
 103             fi
 104           fi
 105           if test "$gl_cv_cc_double_signbit" = unknown; then
 106             dnl Test whether copysign() is declared.
 107             AC_CHECK_DECLS([copysign], , , [[#include <math.h>]])
 108             if test "$ac_cv_have_decl_copysign" = yes; then
 109               dnl Test whether copysign() can be used without libm.
 110               AC_CACHE_CHECK([whether copysign can be used without linking with libm],
 111                 [gl_cv_func_copysign_no_libm],
 112                 [
 113                   AC_LINK_IFELSE(
 114                     [AC_LANG_PROGRAM(
 115                        [[#include <math.h>
 116                          double x, y;]],
 117                        [[return copysign (x, y) < 0;]])],
 118                     [gl_cv_func_copysign_no_libm=yes],
 119                     [gl_cv_func_copysign_no_libm=no])
 120                 ])
 121               if test $gl_cv_func_copysign_no_libm = yes; then
 122                 AC_DEFINE([HAVE_COPYSIGN_IN_LIBC], [1],
 123                   [Define if the copysign function is declared in <math.h> and available in libc.])
 124               fi
 125             fi
 126           fi
 127           if test "$gl_cv_cc_long_double_signbit" = unknown; then
 128             dnl Test whether copysignl() is declared.
 129             AC_CHECK_DECLS([copysignl], , , [[#include <math.h>]])
 130             if test "$ac_cv_have_decl_copysignl" = yes; then
 131               dnl Test whether copysignl() can be used without libm.
 132               AC_CACHE_CHECK([whether copysignl can be used without linking with libm],
 133                 [gl_cv_func_copysignl_no_libm],
 134                 [
 135                   AC_LINK_IFELSE(
 136                     [AC_LANG_PROGRAM(
 137                        [[#include <math.h>
 138                          long double x, y;]],
 139                        [[return copysignl (x, y) < 0;]])],
 140                     [gl_cv_func_copysignl_no_libm=yes],
 141                     [gl_cv_func_copysignl_no_libm=no])
 142                 ])
 143               if test $gl_cv_func_copysignl_no_libm = yes; then
 144                 AC_DEFINE([HAVE_COPYSIGNL_IN_LIBC], [1],
 145                   [Define if the copysignl function is declared in <math.h> and available in libc.])
 146               fi
 147             fi
 148           fi
 149           ;;
 150       esac
 151       ;;
 152   esac
 153 ])
 154
 155 AC_DEFUN([gl_SIGNBIT_TEST_PROGRAM], [[
 156 /* Global variables.
 157    Needed because GCC 4 constant-folds __builtin_signbitl (literal)
 158    but cannot constant-fold            __builtin_signbitl (variable).  */
 159 float vf;
 160 double vd;
 161 long double vl;
 162 int main ()
 163 {
 164 /* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
 165    So we use -p0f and -p0d instead.  */
 166 float p0f = 0.0f;
 167 float m0f = -p0f;
 168 double p0d = 0.0;
 169 double m0d = -p0d;
 170 /* On HP-UX 10.20, negating 0.0L does not yield -0.0L.
 171    So we use another constant expression instead.
 172    But that expression does not work on other platforms, such as when
 173    cross-compiling to PowerPC on Mac OS X 10.5.  */
 174 long double p0l = 0.0L;
 175 #if defined __hpux || defined __sgi
 176 long double m0l = -LDBL_MIN * LDBL_MIN;
 177 #else
 178 long double m0l = -p0l;
 179 #endif
 180   int result = 0;
 181   if (signbit (vf)) /* link check */
 182     vf++;
 183   {
 184     float plus_inf = 1.0f / p0f;
 185     float minus_inf = -1.0f / p0f;
 186     if (!(!signbit (255.0f)
 187           && signbit (-255.0f)
 188           && !signbit (p0f)
 189           && (memcmp (&m0f, &p0f, sizeof (float)) == 0 || signbit (m0f))
 190           && !signbit (plus_inf)
 191           && signbit (minus_inf)))
 192       result |= 1;
 193   }
 194   if (signbit (vd)) /* link check */
 195     vd++;
 196   {
 197     double plus_inf = 1.0 / p0d;
 198     double minus_inf = -1.0 / p0d;
 199     if (!(!signbit (255.0)
 200           && signbit (-255.0)
 201           && !signbit (p0d)
 202           && (memcmp (&m0d, &p0d, sizeof (double)) == 0 || signbit (m0d))
 203           && !signbit (plus_inf)
 204           && signbit (minus_inf)))
 205       result |= 2;
 206   }
 207   if (signbit (vl)) /* link check */
 208     vl++;
 209   {
 210     long double plus_inf = 1.0L / p0l;
 211     long double minus_inf = -1.0L / p0l;
 212     if (signbit (255.0L))
 213       result |= 4;
 214     if (!signbit (-255.0L))
 215       result |= 4;
 216     if (signbit (p0l))
 217       result |= 8;
 218     if (!(memcmp (&m0l, &p0l, sizeof (long double)) == 0 || signbit (m0l)))
 219       result |= 16;
 220     if (signbit (plus_inf))
 221       result |= 32;
 222     if (!signbit (minus_inf))
 223       result |= 64;
 224   }
 225   return result;
 226 }
 227 ]])
 228
 229 AC_DEFUN([gl_FLOAT_SIGN_LOCATION],
 230 [
 231   gl_FLOATTYPE_SIGN_LOCATION([float], [gl_cv_cc_float_signbit], [f], [FLT])
 232 ])
 233
 234 AC_DEFUN([gl_DOUBLE_SIGN_LOCATION],
 235 [
 236   gl_FLOATTYPE_SIGN_LOCATION([double], [gl_cv_cc_double_signbit], [], [DBL])
 237 ])
 238
 239 AC_DEFUN([gl_LONG_DOUBLE_SIGN_LOCATION],
 240 [
 241   gl_FLOATTYPE_SIGN_LOCATION([long double], [gl_cv_cc_long_double_signbit], [L], [LDBL])
 242 ])
 243
 244 AC_DEFUN([gl_FLOATTYPE_SIGN_LOCATION],
 245 [
 246   AC_CACHE_CHECK([where to find the sign bit in a '$1'],
 247     [$2],
 248     [
 249       AC_RUN_IFELSE(
 250         [AC_LANG_SOURCE([[
 251 #include <stddef.h>
 252 #include <stdio.h>
 253 #define NWORDS \
 254   ((sizeof ($1) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
 255 typedef union { $1 value; unsigned int word[NWORDS]; }
 256         memory_float;
 257 static memory_float plus = { 1.0$3 };
 258 static memory_float minus = { -1.0$3 };
 259 int main ()
 260 {
 261   size_t j, k, i;
 262   unsigned int m;
 263   FILE *fp = fopen ("conftest.out", "w");
 264   if (fp == NULL)
 265     return 1;
 266   /* Find the different bit.  */
 267   k = 0; m = 0;
 268   for (j = 0; j < NWORDS; j++)
 269     {
 270       unsigned int x = plus.word[j] ^ minus.word[j];
 271       if ((x & (x - 1)) || (x && m))
 272         {
 273           /* More than one bit difference.  */
 274           fprintf (fp, "unknown");
 275           return 2;
 276         }
 277       if (x)
 278         {
 279           k = j;
 280           m = x;
 281         }
 282     }
 283   if (m == 0)
 284     {
 285       /* No difference.  */
 286       fprintf (fp, "unknown");
 287       return 3;
 288     }
 289   /* Now m = plus.word[k] ^ ~minus.word[k].  */
 290   if (plus.word[k] & ~minus.word[k])
 291     {
 292       /* Oh? The sign bit is set in the positive and cleared in the negative
 293          numbers?  */
 294       fprintf (fp, "unknown");
 295       return 4;
 296     }
 297   for (i = 0; ; i++)
 298     if ((m >> i) & 1)
 299       break;
 300   fprintf (fp, "word %d bit %d", (int) k, (int) i);
 301   if (fclose (fp) != 0)
 302     return 5;
 303   return 0;
 304 }
 305         ]])],
 306         [$2=`cat conftest.out`],
 307         [$2="unknown"],
 308         [
 309           dnl When cross-compiling, we don't know. It depends on the
 310           dnl ABI and compiler version. There are too many cases.
 311           $2="unknown"
 312         ])
 313       rm -f conftest.out
 314     ])
 315   case "$]$2[" in
 316     word*bit*)
 317       word=`echo "$]$2[" | sed -e 's/word //' -e 's/ bit.*//'`
 318       bit=`echo "$]$2[" | sed -e 's/word.*bit //'`
 319       AC_DEFINE_UNQUOTED([$4][_SIGNBIT_WORD], [$word],
 320         [Define as the word index where to find the sign of '$1'.])
 321       AC_DEFINE_UNQUOTED([$4][_SIGNBIT_BIT], [$bit],
 322         [Define as the bit index in the word where to find the sign of '$1'.])
 323       ;;
 324   esac
 325 ])
 326
 327 # Expands to code that defines a function signbitf(float).
 328 # It extracts the sign bit of a non-NaN value.
 329 AC_DEFUN([gl_FLOAT_SIGNBIT_CODE],
 330 [
 331   gl_FLOATTYPE_SIGNBIT_CODE([float], [f], [f])
 332 ])
 333
 334 # Expands to code that defines a function signbitd(double).
 335 # It extracts the sign bit of a non-NaN value.
 336 AC_DEFUN([gl_DOUBLE_SIGNBIT_CODE],
 337 [
 338   gl_FLOATTYPE_SIGNBIT_CODE([double], [d], [])
 339 ])
 340
 341 # Expands to code that defines a function signbitl(long double).
 342 # It extracts the sign bit of a non-NaN value.
 343 AC_DEFUN([gl_LONG_DOUBLE_SIGNBIT_CODE],
 344 [
 345   gl_FLOATTYPE_SIGNBIT_CODE([long double], [l], [L])
 346 ])
 347
 348 AC_DEFUN([gl_FLOATTYPE_SIGNBIT_CODE],
 349 [[
 350 static int
 351 signbit$2 ($1 value)
 352 {
 353   typedef union { $1 f; unsigned char b[sizeof ($1)]; } float_union;
 354   static float_union plus_one = { 1.0$3 };   /* unused bits are zero here */
 355   static float_union minus_one = { -1.0$3 }; /* unused bits are zero here */
 356   /* Compute the sign bit mask as the XOR of plus_one and minus_one.  */
 357   float_union u;
 358   unsigned int i;
 359   u.f = value;
 360   for (i = 0; i < sizeof ($1); i++)
 361     if (u.b[i] & (plus_one.b[i] ^ minus_one.b[i]))
 362       return 1;
 363   return 0;
 364 }
 365 ]])