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Diffstat (limited to 'm4/exponentd.m4')
| -rw-r--r-- | m4/exponentd.m4 | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/m4/exponentd.m4 b/m4/exponentd.m4 new file mode 100644 index 0000000..cca8797 --- /dev/null +++ b/m4/exponentd.m4 @@ -0,0 +1,116 @@ +# exponentd.m4 serial 3 +dnl Copyright (C) 2007-2008, 2010-2020 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_DOUBLE_EXPONENT_LOCATION], +[ + AC_CACHE_CHECK([where to find the exponent in a 'double'], + [gl_cv_cc_double_expbit0], + [ + AC_RUN_IFELSE( + [AC_LANG_SOURCE([[ +#include <float.h> +#include <stddef.h> +#include <stdio.h> +#include <string.h> +#define NWORDS \ + ((sizeof (double) + sizeof (unsigned int) - 1) / sizeof (unsigned int)) +typedef union { double value; unsigned int word[NWORDS]; } memory_double; +static unsigned int ored_words[NWORDS]; +static unsigned int anded_words[NWORDS]; +static void add_to_ored_words (double x) +{ + memory_double m; + size_t i; + /* Clear it first, in case sizeof (double) < sizeof (memory_double). */ + memset (&m, 0, sizeof (memory_double)); + m.value = x; + for (i = 0; i < NWORDS; i++) + { + ored_words[i] |= m.word[i]; + anded_words[i] &= m.word[i]; + } +} +int main () +{ + size_t j; + FILE *fp = fopen ("conftest.out", "w"); + if (fp == NULL) + return 1; + for (j = 0; j < NWORDS; j++) + anded_words[j] = ~ (unsigned int) 0; + add_to_ored_words (0.25); + add_to_ored_words (0.5); + add_to_ored_words (1.0); + add_to_ored_words (2.0); + add_to_ored_words (4.0); + /* Remove bits that are common (e.g. if representation of the first mantissa + bit is explicit). */ + for (j = 0; j < NWORDS; j++) + ored_words[j] &= ~anded_words[j]; + /* Now find the nonzero word. */ + for (j = 0; j < NWORDS; j++) + if (ored_words[j] != 0) + break; + if (j < NWORDS) + { + size_t i; + for (i = j + 1; i < NWORDS; i++) + if (ored_words[i] != 0) + { + fprintf (fp, "unknown"); + return (fclose (fp) != 0); + } + for (i = 0; ; i++) + if ((ored_words[j] >> i) & 1) + { + fprintf (fp, "word %d bit %d", (int) j, (int) i); + return (fclose (fp) != 0); + } + } + fprintf (fp, "unknown"); + return (fclose (fp) != 0); +} + ]])], + [gl_cv_cc_double_expbit0=`cat conftest.out`], + [gl_cv_cc_double_expbit0="unknown"], + [ + dnl On ARM, there are two 'double' floating-point formats, used by + dnl different sets of instructions: The older FPA instructions assume + dnl that they are stored in big-endian word order, while the words + dnl (like integer types) are stored in little-endian byte order. + dnl The newer VFP instructions assume little-endian order + dnl consistently. + AC_EGREP_CPP([mixed_endianness], [ +#if defined arm || defined __arm || defined __arm__ + mixed_endianness +#endif + ], + [gl_cv_cc_double_expbit0="unknown"], + [ + pushdef([AC_MSG_CHECKING],[:])dnl + pushdef([AC_MSG_RESULT],[:])dnl + pushdef([AC_MSG_RESULT_UNQUOTED],[:])dnl + AC_C_BIGENDIAN( + [gl_cv_cc_double_expbit0="word 0 bit 20"], + [gl_cv_cc_double_expbit0="word 1 bit 20"], + [gl_cv_cc_double_expbit0="unknown"]) + popdef([AC_MSG_RESULT_UNQUOTED])dnl + popdef([AC_MSG_RESULT])dnl + popdef([AC_MSG_CHECKING])dnl + ]) + ]) + rm -f conftest.out + ]) + case "$gl_cv_cc_double_expbit0" in + word*bit*) + word=`echo "$gl_cv_cc_double_expbit0" | sed -e 's/word //' -e 's/ bit.*//'` + bit=`echo "$gl_cv_cc_double_expbit0" | sed -e 's/word.*bit //'` + AC_DEFINE_UNQUOTED([DBL_EXPBIT0_WORD], [$word], + [Define as the word index where to find the exponent of 'double'.]) + AC_DEFINE_UNQUOTED([DBL_EXPBIT0_BIT], [$bit], + [Define as the bit index in the word where to find bit 0 of the exponent of 'double'.]) + ;; + esac +]) |