1 # exponentd.m4 serial 1
2 dnl Copyright (C) 2007-2010 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 AC_DEFUN([gl_DOUBLE_EXPONENT_LOCATION],
8 AC_CACHE_CHECK([where to find the exponent in a 'double'],
9 [gl_cv_cc_double_expbit0],
17 ((sizeof (double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
18 typedef union { double value; unsigned int word[NWORDS]; } memory_double;
19 static unsigned int ored_words[NWORDS];
20 static unsigned int anded_words[NWORDS];
21 static void add_to_ored_words (double x)
25 /* Clear it first, in case sizeof (double) < sizeof (memory_double). */
26 memset (&m, 0, sizeof (memory_double));
28 for (i = 0; i < NWORDS; i++)
30 ored_words[i] |= m.word[i];
31 anded_words[i] &= m.word[i];
37 FILE *fp = fopen ("conftest.out", "w");
40 for (j = 0; j < NWORDS; j++)
41 anded_words[j] = ~ (unsigned int) 0;
42 add_to_ored_words (0.25);
43 add_to_ored_words (0.5);
44 add_to_ored_words (1.0);
45 add_to_ored_words (2.0);
46 add_to_ored_words (4.0);
47 /* Remove bits that are common (e.g. if representation of the first mantissa
49 for (j = 0; j < NWORDS; j++)
50 ored_words[j] &= ~anded_words[j];
51 /* Now find the nonzero word. */
52 for (j = 0; j < NWORDS; j++)
53 if (ored_words[j] != 0)
58 for (i = j + 1; i < NWORDS; i++)
59 if (ored_words[i] != 0)
61 fprintf (fp, "unknown");
62 return (fclose (fp) != 0);
65 if ((ored_words[j] >> i) & 1)
67 fprintf (fp, "word %d bit %d", (int) j, (int) i);
68 return (fclose (fp) != 0);
71 fprintf (fp, "unknown");
72 return (fclose (fp) != 0);
75 [gl_cv_cc_double_expbit0=`cat conftest.out`],
76 [gl_cv_cc_double_expbit0="unknown"],
78 dnl On ARM, there are two 'double' floating-point formats, used by
79 dnl different sets of instructions: The older FPA instructions assume
80 dnl that they are stored in big-endian word order, while the words
81 dnl (like integer types) are stored in little-endian byte order.
82 dnl The newer VFP instructions assume little-endian order consistenly.
83 AC_EGREP_CPP([mixed_endianness], [
84 #if defined arm || defined __arm || defined __arm__
88 [gl_cv_cc_double_expbit0="unknown"],
90 pushdef([AC_MSG_CHECKING],[:])dnl
91 pushdef([AC_MSG_RESULT],[:])dnl
92 pushdef([AC_MSG_RESULT_UNQUOTED],[:])dnl
94 [gl_cv_cc_double_expbit0="word 0 bit 20"],
95 [gl_cv_cc_double_expbit0="word 1 bit 20"],
96 [gl_cv_cc_double_expbit0="unknown"])
97 popdef([AC_MSG_RESULT_UNQUOTED])dnl
98 popdef([AC_MSG_RESULT])dnl
99 popdef([AC_MSG_CHECKING])dnl
104 case "$gl_cv_cc_double_expbit0" in
106 word=`echo "$gl_cv_cc_double_expbit0" | sed -e 's/word //' -e 's/ bit.*//'`
107 bit=`echo "$gl_cv_cc_double_expbit0" | sed -e 's/word.*bit //'`
108 AC_DEFINE_UNQUOTED([DBL_EXPBIT0_WORD], [$word],
109 [Define as the word index where to find the exponent of 'double'.])
110 AC_DEFINE_UNQUOTED([DBL_EXPBIT0_BIT], [$bit],
111 [Define as the bit index in the word where to find bit 0 of the exponent of 'double'.])