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maint: Run 'make update-copyright'
author Paul Eggert <eggert@cs.ucla.edu>
date Tue, 01 Jan 2019 00:25:11 +0100
parents 10eb9086bea0
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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Paul Eggert <eggert@cs.ucla.edu>
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1 # exponentd.m4 serial 3
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2 dnl Copyright (C) 2007-2008, 2010-2019 Free Software Foundation, Inc.
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3 dnl This file is free software; the Free Software Foundation
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4 dnl gives unlimited permission to copy and/or distribute it,
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5 dnl with or without modifications, as long as this notice is preserved.
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6 AC_DEFUN([gl_DOUBLE_EXPONENT_LOCATION],
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7 [
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8 AC_CACHE_CHECK([where to find the exponent in a 'double'],
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9 [gl_cv_cc_double_expbit0],
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10 [
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11 AC_RUN_IFELSE(
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12 [AC_LANG_SOURCE([[
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13 #include <float.h>
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14 #include <stddef.h>
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15 #include <stdio.h>
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16 #include <string.h>
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17 #define NWORDS \
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18 ((sizeof (double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
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19 typedef union { double value; unsigned int word[NWORDS]; } memory_double;
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20 static unsigned int ored_words[NWORDS];
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21 static unsigned int anded_words[NWORDS];
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22 static void add_to_ored_words (double x)
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23 {
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24 memory_double m;
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25 size_t i;
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26 /* Clear it first, in case sizeof (double) < sizeof (memory_double). */
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27 memset (&m, 0, sizeof (memory_double));
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28 m.value = x;
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29 for (i = 0; i < NWORDS; i++)
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30 {
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31 ored_words[i] |= m.word[i];
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32 anded_words[i] &= m.word[i];
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33 }
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34 }
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35 int main ()
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36 {
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37 size_t j;
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38 FILE *fp = fopen ("conftest.out", "w");
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39 if (fp == NULL)
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40 return 1;
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41 for (j = 0; j < NWORDS; j++)
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42 anded_words[j] = ~ (unsigned int) 0;
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43 add_to_ored_words (0.25);
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44 add_to_ored_words (0.5);
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45 add_to_ored_words (1.0);
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46 add_to_ored_words (2.0);
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47 add_to_ored_words (4.0);
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48 /* Remove bits that are common (e.g. if representation of the first mantissa
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49 bit is explicit). */
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50 for (j = 0; j < NWORDS; j++)
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51 ored_words[j] &= ~anded_words[j];
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52 /* Now find the nonzero word. */
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53 for (j = 0; j < NWORDS; j++)
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54 if (ored_words[j] != 0)
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55 break;
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56 if (j < NWORDS)
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57 {
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58 size_t i;
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59 for (i = j + 1; i < NWORDS; i++)
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60 if (ored_words[i] != 0)
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61 {
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62 fprintf (fp, "unknown");
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63 return (fclose (fp) != 0);
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64 }
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65 for (i = 0; ; i++)
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66 if ((ored_words[j] >> i) & 1)
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67 {
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68 fprintf (fp, "word %d bit %d", (int) j, (int) i);
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69 return (fclose (fp) != 0);
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70 }
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71 }
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72 fprintf (fp, "unknown");
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73 return (fclose (fp) != 0);
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74 }
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75 ]])],
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76 [gl_cv_cc_double_expbit0=`cat conftest.out`],
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77 [gl_cv_cc_double_expbit0="unknown"],
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78 [
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79 dnl On ARM, there are two 'double' floating-point formats, used by
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80 dnl different sets of instructions: The older FPA instructions assume
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81 dnl that they are stored in big-endian word order, while the words
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82 dnl (like integer types) are stored in little-endian byte order.
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83 dnl The newer VFP instructions assume little-endian order
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84 dnl consistently.
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85 AC_EGREP_CPP([mixed_endianness], [
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86 #if defined arm || defined __arm || defined __arm__
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87 mixed_endianness
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88 #endif
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89 ],
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90 [gl_cv_cc_double_expbit0="unknown"],
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91 [
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92 pushdef([AC_MSG_CHECKING],[:])dnl
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93 pushdef([AC_MSG_RESULT],[:])dnl
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94 pushdef([AC_MSG_RESULT_UNQUOTED],[:])dnl
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95 AC_C_BIGENDIAN(
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96 [gl_cv_cc_double_expbit0="word 0 bit 20"],
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97 [gl_cv_cc_double_expbit0="word 1 bit 20"],
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98 [gl_cv_cc_double_expbit0="unknown"])
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99 popdef([AC_MSG_RESULT_UNQUOTED])dnl
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100 popdef([AC_MSG_RESULT])dnl
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101 popdef([AC_MSG_CHECKING])dnl
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102 ])
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103 ])
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104 rm -f conftest.out
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105 ])
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106 case "$gl_cv_cc_double_expbit0" in
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107 word*bit*)
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108 word=`echo "$gl_cv_cc_double_expbit0" | sed -e 's/word //' -e 's/ bit.*//'`
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109 bit=`echo "$gl_cv_cc_double_expbit0" | sed -e 's/word.*bit //'`
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110 AC_DEFINE_UNQUOTED([DBL_EXPBIT0_WORD], [$word],
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111 [Define as the word index where to find the exponent of 'double'.])
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112 AC_DEFINE_UNQUOTED([DBL_EXPBIT0_BIT], [$bit],
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113 [Define as the bit index in the word where to find bit 0 of the exponent of 'double'.])
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114 ;;
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115 esac
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116 ])