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Diffstat (limited to 'm4/signbit.m4')
| -rw-r--r-- | m4/signbit.m4 | 392 |
1 files changed, 392 insertions, 0 deletions
diff --git a/m4/signbit.m4 b/m4/signbit.m4 new file mode 100644 index 0000000..73d96ea --- /dev/null +++ b/m4/signbit.m4 @@ -0,0 +1,392 @@ +# signbit.m4 serial 19 +dnl Copyright (C) 2007-2020 Free Software Foundation, Inc. +dnl This file is free software; the Free Software Foundation +dnl gives unlimited permission to copy and/or distribute it, +dnl with or without modifications, as long as this notice is preserved. + +AC_DEFUN([gl_SIGNBIT], +[ + AC_REQUIRE([gl_MATH_H_DEFAULTS]) + AC_REQUIRE([AC_CANONICAL_HOST]) + AC_CACHE_CHECK([for signbit macro], [gl_cv_func_signbit], + [ + AC_RUN_IFELSE( + [AC_LANG_SOURCE([[ +#include <math.h> +/* If signbit is defined as a function, don't use it, since calling it for + 'float' or 'long double' arguments would involve conversions. + If signbit is not declared at all but exists as a library function, don't + use it, since the prototype may not match. + If signbit is not declared at all but exists as a compiler built-in, don't + use it, since it's preferable to use __builtin_signbit* (no warnings, + no conversions). */ +#ifndef signbit +# error "signbit should be a macro" +#endif +#include <string.h> +]gl_SIGNBIT_TEST_PROGRAM +])], + [gl_cv_func_signbit=yes], + [gl_cv_func_signbit=no], + [case "$host_os" in + # Guess yes on glibc systems. + *-gnu* | gnu*) gl_cv_func_signbit="guessing yes" ;; + # Guess yes on musl systems. + *-musl*) gl_cv_func_signbit="guessing yes" ;; + # Guess yes on native Windows. + mingw*) gl_cv_func_signbit="guessing yes" ;; + # If we don't know, obey --enable-cross-guesses. + *) gl_cv_func_signbit="$gl_cross_guess_normal" ;; + esac + ]) + ]) + dnl GCC 4.0 and newer provides three built-ins for signbit. + dnl They can be used without warnings, also in C++, regardless of <math.h>. + dnl But they may expand to calls to functions, which may or may not be in + dnl libc. + AC_CACHE_CHECK([for signbit compiler built-ins], [gl_cv_func_signbit_gcc], + [ + AC_RUN_IFELSE( + [AC_LANG_SOURCE([[ +#if __GNUC__ >= 4 +# define signbit(x) \ + (sizeof (x) == sizeof (long double) ? __builtin_signbitl (x) : \ + sizeof (x) == sizeof (double) ? __builtin_signbit (x) : \ + __builtin_signbitf (x)) +#else +# error "signbit should be three compiler built-ins" +#endif +#include <string.h> +]gl_SIGNBIT_TEST_PROGRAM +])], + [gl_cv_func_signbit_gcc=yes], + [gl_cv_func_signbit_gcc=no], + [case "$host_os" in + # Guess yes on glibc systems. + *-gnu* | gnu*) gl_cv_func_signbit_gcc="guessing yes" ;; + # Guess yes on musl systems. + *-musl*) gl_cv_func_signbit_gcc="guessing yes" ;; + # Guess yes on mingw, no on MSVC. + mingw*) if test -n "$GCC"; then + gl_cv_func_signbit_gcc="guessing yes" + else + gl_cv_func_signbit_gcc="guessing no" + fi + ;; + # If we don't know, obey --enable-cross-guesses. + *) gl_cv_func_signbit_gcc="$gl_cross_guess_normal" ;; + esac + ]) + ]) + dnl Use the compiler built-ins whenever possible, because they are more + dnl efficient than the system library functions (if they exist). + case "$gl_cv_func_signbit_gcc" in + *yes) + REPLACE_SIGNBIT_USING_GCC=1 + ;; + *) + case "$gl_cv_func_signbit" in + *yes) ;; + *) + dnl REPLACE_SIGNBIT=1 makes sure the signbit[fdl] functions get built. + REPLACE_SIGNBIT=1 + ;; + esac + ;; + esac + dnl On Solaris 10, with CC in C++ mode, signbit is not available although + dnl is with cc in C mode. This cannot be worked around by defining + dnl _XOPEN_SOURCE=600, because the latter does not work in C++ mode on + dnl Solaris 11.0. Therefore use the replacement functions on Solaris. + case "$host_os" in + solaris*) + REPLACE_SIGNBIT=1 + ;; + esac + if test $REPLACE_SIGNBIT = 1; then + gl_FLOAT_SIGN_LOCATION + gl_DOUBLE_SIGN_LOCATION + gl_LONG_DOUBLE_SIGN_LOCATION + if test "$gl_cv_cc_float_signbit" = unknown; then + dnl Test whether copysignf() is declared. + AC_CHECK_DECLS([copysignf], , , [[#include <math.h>]]) + if test "$ac_cv_have_decl_copysignf" = yes; then + dnl Test whether copysignf() can be used without libm. + AC_CACHE_CHECK([whether copysignf can be used without linking with libm], + [gl_cv_func_copysignf_no_libm], + [ + AC_LINK_IFELSE( + [AC_LANG_PROGRAM( + [[#include <math.h> + float x, y;]], + [[return copysignf (x, y) < 0;]])], + [gl_cv_func_copysignf_no_libm=yes], + [gl_cv_func_copysignf_no_libm=no]) + ]) + if test $gl_cv_func_copysignf_no_libm = yes; then + AC_DEFINE([HAVE_COPYSIGNF_IN_LIBC], [1], + [Define if the copysignf function is declared in <math.h> and available in libc.]) + fi + fi + fi + if test "$gl_cv_cc_double_signbit" = unknown; then + dnl Test whether copysign() is declared. + AC_CHECK_DECLS([copysign], , , [[#include <math.h>]]) + if test "$ac_cv_have_decl_copysign" = yes; then + dnl Test whether copysign() can be used without libm. + AC_CACHE_CHECK([whether copysign can be used without linking with libm], + [gl_cv_func_copysign_no_libm], + [ + AC_LINK_IFELSE( + [AC_LANG_PROGRAM( + [[#include <math.h> + double x, y;]], + [[return copysign (x, y) < 0;]])], + [gl_cv_func_copysign_no_libm=yes], + [gl_cv_func_copysign_no_libm=no]) + ]) + if test $gl_cv_func_copysign_no_libm = yes; then + AC_DEFINE([HAVE_COPYSIGN_IN_LIBC], [1], + [Define if the copysign function is declared in <math.h> and available in libc.]) + fi + fi + fi + if test "$gl_cv_cc_long_double_signbit" = unknown; then + dnl Test whether copysignl() is declared. + AC_CHECK_DECLS([copysignl], , , [[#include <math.h>]]) + if test "$ac_cv_have_decl_copysignl" = yes; then + dnl Test whether copysignl() can be used without libm. + AC_CACHE_CHECK([whether copysignl can be used without linking with libm], + [gl_cv_func_copysignl_no_libm], + [ + AC_LINK_IFELSE( + [AC_LANG_PROGRAM( + [[#include <math.h> + long double x, y;]], + [[return copysignl (x, y) < 0;]])], + [gl_cv_func_copysignl_no_libm=yes], + [gl_cv_func_copysignl_no_libm=no]) + ]) + if test $gl_cv_func_copysignl_no_libm = yes; then + AC_DEFINE([HAVE_COPYSIGNL_IN_LIBC], [1], + [Define if the copysignl function is declared in <math.h> and available in libc.]) + fi + fi + fi + fi +]) + +AC_DEFUN([gl_SIGNBIT_TEST_PROGRAM], [[ +/* Global variables. + Needed because GCC 4 constant-folds __builtin_signbitl (literal) + but cannot constant-fold __builtin_signbitl (variable). */ +float vf; +double vd; +long double vl; +int main () +{ +/* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0. + So we use -p0f and -p0d instead. */ +float p0f = 0.0f; +float m0f = -p0f; +double p0d = 0.0; +double m0d = -p0d; +/* On HP-UX 10.20, negating 0.0L does not yield -0.0L. + So we use another constant expression instead. + But that expression does not work on other platforms, such as when + cross-compiling to PowerPC on Mac OS X 10.5. */ +long double p0l = 0.0L; +#if defined __hpux || defined __sgi +long double m0l = -LDBL_MIN * LDBL_MIN; +#else +long double m0l = -p0l; +#endif + int result = 0; + if (signbit (vf)) /* link check */ + vf++; + { + float plus_inf = 1.0f / p0f; + float minus_inf = -1.0f / p0f; + if (!(!signbit (255.0f) + && signbit (-255.0f) + && !signbit (p0f) + && (memcmp (&m0f, &p0f, sizeof (float)) == 0 || signbit (m0f)) + && !signbit (plus_inf) + && signbit (minus_inf))) + result |= 1; + } + if (signbit (vd)) /* link check */ + vd++; + { + double plus_inf = 1.0 / p0d; + double minus_inf = -1.0 / p0d; + if (!(!signbit (255.0) + && signbit (-255.0) + && !signbit (p0d) + && (memcmp (&m0d, &p0d, sizeof (double)) == 0 || signbit (m0d)) + && !signbit (plus_inf) + && signbit (minus_inf))) + result |= 2; + } + if (signbit (vl)) /* link check */ + vl++; + { + long double plus_inf = 1.0L / p0l; + long double minus_inf = -1.0L / p0l; + if (signbit (255.0L)) + result |= 4; + if (!signbit (-255.0L)) + result |= 4; + if (signbit (p0l)) + result |= 8; + if (!(memcmp (&m0l, &p0l, sizeof (long double)) == 0 || signbit (m0l))) + result |= 16; + if (signbit (plus_inf)) + result |= 32; + if (!signbit (minus_inf)) + result |= 64; + } + return result; +} +]]) + +AC_DEFUN([gl_FLOAT_SIGN_LOCATION], +[ + gl_FLOATTYPE_SIGN_LOCATION([float], [gl_cv_cc_float_signbit], [f], [FLT]) +]) + +AC_DEFUN([gl_DOUBLE_SIGN_LOCATION], +[ + gl_FLOATTYPE_SIGN_LOCATION([double], [gl_cv_cc_double_signbit], [], [DBL]) +]) + +AC_DEFUN([gl_LONG_DOUBLE_SIGN_LOCATION], +[ + gl_FLOATTYPE_SIGN_LOCATION([long double], [gl_cv_cc_long_double_signbit], [L], [LDBL]) +]) + +AC_DEFUN([gl_FLOATTYPE_SIGN_LOCATION], +[ + AC_CACHE_CHECK([where to find the sign bit in a '$1'], + [$2], + [ + AC_RUN_IFELSE( + [AC_LANG_SOURCE([[ +#include <stddef.h> +#include <stdio.h> +#define NWORDS \ + ((sizeof ($1) + sizeof (unsigned int) - 1) / sizeof (unsigned int)) +typedef union { $1 value; unsigned int word[NWORDS]; } + memory_float; +static memory_float plus = { 1.0$3 }; +static memory_float minus = { -1.0$3 }; +int main () +{ + size_t j, k, i; + unsigned int m; + FILE *fp = fopen ("conftest.out", "w"); + if (fp == NULL) + return 1; + /* Find the different bit. */ + k = 0; m = 0; + for (j = 0; j < NWORDS; j++) + { + unsigned int x = plus.word[j] ^ minus.word[j]; + if ((x & (x - 1)) || (x && m)) + { + /* More than one bit difference. */ + fprintf (fp, "unknown"); + fclose (fp); + return 2; + } + if (x) + { + k = j; + m = x; + } + } + if (m == 0) + { + /* No difference. */ + fprintf (fp, "unknown"); + fclose (fp); + return 3; + } + /* Now m = plus.word[k] ^ ~minus.word[k]. */ + if (plus.word[k] & ~minus.word[k]) + { + /* Oh? The sign bit is set in the positive and cleared in the negative + numbers? */ + fprintf (fp, "unknown"); + fclose (fp); + return 4; + } + for (i = 0; ; i++) + if ((m >> i) & 1) + break; + fprintf (fp, "word %d bit %d", (int) k, (int) i); + if (fclose (fp) != 0) + return 5; + return 0; +} + ]])], + [$2=`cat conftest.out`], + [$2="unknown"], + [ + dnl When cross-compiling, we don't know. It depends on the + dnl ABI and compiler version. There are too many cases. + $2="unknown" + ]) + rm -f conftest.out + ]) + case "$]$2[" in + word*bit*) + word=`echo "$]$2[" | sed -e 's/word //' -e 's/ bit.*//'` + bit=`echo "$]$2[" | sed -e 's/word.*bit //'` + AC_DEFINE_UNQUOTED([$4][_SIGNBIT_WORD], [$word], + [Define as the word index where to find the sign of '$1'.]) + AC_DEFINE_UNQUOTED([$4][_SIGNBIT_BIT], [$bit], + [Define as the bit index in the word where to find the sign of '$1'.]) + ;; + esac +]) + +# Expands to code that defines a function signbitf(float). +# It extracts the sign bit of a non-NaN value. +AC_DEFUN([gl_FLOAT_SIGNBIT_CODE], +[ + gl_FLOATTYPE_SIGNBIT_CODE([float], [f], [f]) +]) + +# Expands to code that defines a function signbitd(double). +# It extracts the sign bit of a non-NaN value. +AC_DEFUN([gl_DOUBLE_SIGNBIT_CODE], +[ + gl_FLOATTYPE_SIGNBIT_CODE([double], [d], []) +]) + +# Expands to code that defines a function signbitl(long double). +# It extracts the sign bit of a non-NaN value. +AC_DEFUN([gl_LONG_DOUBLE_SIGNBIT_CODE], +[ + gl_FLOATTYPE_SIGNBIT_CODE([long double], [l], [L]) +]) + +AC_DEFUN([gl_FLOATTYPE_SIGNBIT_CODE], +[[ +static int +signbit$2 ($1 value) +{ + typedef union { $1 f; unsigned char b[sizeof ($1)]; } float_union; + static float_union plus_one = { 1.0$3 }; /* unused bits are zero here */ + static float_union minus_one = { -1.0$3 }; /* unused bits are zero here */ + /* Compute the sign bit mask as the XOR of plus_one and minus_one. */ + float_union u; + unsigned int i; + u.f = value; + for (i = 0; i < sizeof ($1); i++) + if (u.b[i] & (plus_one.b[i] ^ minus_one.b[i])) + return 1; + return 0; +} +]]) |