| # exponentd.m4 serial 3 |
| dnl Copyright (C) 2007-2008, 2010-2021 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 |
| ]) |