Commit | Line | Data |
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88b48903 | 1 | # exponentd.m4 serial 3 |
4a626d0a | 2 | dnl Copyright (C) 2007-2008, 2010-2015 Free Software Foundation, Inc. |
88b48903 WN |
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], | |
7 | [ | |
8 | AC_CACHE_CHECK([where to find the exponent in a 'double'], | |
9 | [gl_cv_cc_double_expbit0], | |
10 | [ | |
11 | AC_RUN_IFELSE( | |
12 | [AC_LANG_SOURCE([[ | |
13 | #include <float.h> | |
14 | #include <stddef.h> | |
15 | #include <stdio.h> | |
16 | #include <string.h> | |
17 | #define NWORDS \ | |
18 | ((sizeof (double) + sizeof (unsigned int) - 1) / sizeof (unsigned int)) | |
19 | typedef union { double value; unsigned int word[NWORDS]; } memory_double; | |
20 | static unsigned int ored_words[NWORDS]; | |
21 | static unsigned int anded_words[NWORDS]; | |
22 | static void add_to_ored_words (double x) | |
23 | { | |
24 | memory_double m; | |
25 | size_t i; | |
26 | /* Clear it first, in case sizeof (double) < sizeof (memory_double). */ | |
27 | memset (&m, 0, sizeof (memory_double)); | |
28 | m.value = x; | |
29 | for (i = 0; i < NWORDS; i++) | |
30 | { | |
31 | ored_words[i] |= m.word[i]; | |
32 | anded_words[i] &= m.word[i]; | |
33 | } | |
34 | } | |
35 | int main () | |
36 | { | |
37 | size_t j; | |
38 | FILE *fp = fopen ("conftest.out", "w"); | |
39 | if (fp == NULL) | |
40 | return 1; | |
41 | for (j = 0; j < NWORDS; j++) | |
42 | anded_words[j] = ~ (unsigned int) 0; | |
43 | add_to_ored_words (0.25); | |
44 | add_to_ored_words (0.5); | |
45 | add_to_ored_words (1.0); | |
46 | add_to_ored_words (2.0); | |
47 | add_to_ored_words (4.0); | |
48 | /* Remove bits that are common (e.g. if representation of the first mantissa | |
49 | bit is explicit). */ | |
50 | for (j = 0; j < NWORDS; j++) | |
51 | ored_words[j] &= ~anded_words[j]; | |
52 | /* Now find the nonzero word. */ | |
53 | for (j = 0; j < NWORDS; j++) | |
54 | if (ored_words[j] != 0) | |
55 | break; | |
56 | if (j < NWORDS) | |
57 | { | |
58 | size_t i; | |
59 | for (i = j + 1; i < NWORDS; i++) | |
60 | if (ored_words[i] != 0) | |
61 | { | |
62 | fprintf (fp, "unknown"); | |
63 | return (fclose (fp) != 0); | |
64 | } | |
65 | for (i = 0; ; i++) | |
66 | if ((ored_words[j] >> i) & 1) | |
67 | { | |
68 | fprintf (fp, "word %d bit %d", (int) j, (int) i); | |
69 | return (fclose (fp) != 0); | |
70 | } | |
71 | } | |
72 | fprintf (fp, "unknown"); | |
73 | return (fclose (fp) != 0); | |
74 | } | |
75 | ]])], | |
76 | [gl_cv_cc_double_expbit0=`cat conftest.out`], | |
77 | [gl_cv_cc_double_expbit0="unknown"], | |
78 | [ | |
79 | dnl On ARM, there are two 'double' floating-point formats, used by | |
80 | dnl different sets of instructions: The older FPA instructions assume | |
81 | dnl that they are stored in big-endian word order, while the words | |
82 | dnl (like integer types) are stored in little-endian byte order. | |
83 | dnl The newer VFP instructions assume little-endian order | |
84 | dnl consistently. | |
85 | AC_EGREP_CPP([mixed_endianness], [ | |
86 | #if defined arm || defined __arm || defined __arm__ | |
87 | mixed_endianness | |
88 | #endif | |
89 | ], | |
90 | [gl_cv_cc_double_expbit0="unknown"], | |
91 | [ | |
92 | pushdef([AC_MSG_CHECKING],[:])dnl | |
93 | pushdef([AC_MSG_RESULT],[:])dnl | |
94 | pushdef([AC_MSG_RESULT_UNQUOTED],[:])dnl | |
95 | AC_C_BIGENDIAN( | |
96 | [gl_cv_cc_double_expbit0="word 0 bit 20"], | |
97 | [gl_cv_cc_double_expbit0="word 1 bit 20"], | |
98 | [gl_cv_cc_double_expbit0="unknown"]) | |
99 | popdef([AC_MSG_RESULT_UNQUOTED])dnl | |
100 | popdef([AC_MSG_RESULT])dnl | |
101 | popdef([AC_MSG_CHECKING])dnl | |
102 | ]) | |
103 | ]) | |
104 | rm -f conftest.out | |
105 | ]) | |
106 | case "$gl_cv_cc_double_expbit0" in | |
107 | word*bit*) | |
108 | word=`echo "$gl_cv_cc_double_expbit0" | sed -e 's/word //' -e 's/ bit.*//'` | |
109 | bit=`echo "$gl_cv_cc_double_expbit0" | sed -e 's/word.*bit //'` | |
110 | AC_DEFINE_UNQUOTED([DBL_EXPBIT0_WORD], [$word], | |
111 | [Define as the word index where to find the exponent of 'double'.]) | |
112 | AC_DEFINE_UNQUOTED([DBL_EXPBIT0_BIT], [$bit], | |
113 | [Define as the bit index in the word where to find bit 0 of the exponent of 'double'.]) | |
114 | ;; | |
115 | esac | |
116 | ]) |