1 # signbit.m4 serial 13 2 dnl Copyright (C) 2007-2012 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 ]]) 366
