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698be2d8 | 1 | # exponentl.m4 serial 5 |
dc6c21da | 2 | dnl Copyright (C) 2007-2022 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_LONG_DOUBLE_EXPONENT_LOCATION], | |
7 | [ | |
8 | AC_REQUIRE([gl_BIGENDIAN]) | |
c0c3707f | 9 | AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles |
88b48903 WN |
10 | AC_CACHE_CHECK([where to find the exponent in a 'long double'], |
11 | [gl_cv_cc_long_double_expbit0], | |
12 | [ | |
13 | AC_RUN_IFELSE( | |
14 | [AC_LANG_SOURCE([[ | |
15 | #include <float.h> | |
16 | #include <stddef.h> | |
17 | #include <stdio.h> | |
18 | #include <string.h> | |
19 | #define NWORDS \ | |
20 | ((sizeof (long double) + sizeof (unsigned int) - 1) / sizeof (unsigned int)) | |
21 | typedef union { long double value; unsigned int word[NWORDS]; } | |
22 | memory_long_double; | |
23 | static unsigned int ored_words[NWORDS]; | |
24 | static unsigned int anded_words[NWORDS]; | |
698be2d8 | 25 | static void add_to_ored_words (long double *x) |
88b48903 WN |
26 | { |
27 | memory_long_double m; | |
28 | size_t i; | |
29 | /* Clear it first, in case | |
30 | sizeof (long double) < sizeof (memory_long_double). */ | |
31 | memset (&m, 0, sizeof (memory_long_double)); | |
698be2d8 | 32 | m.value = *x; |
88b48903 WN |
33 | for (i = 0; i < NWORDS; i++) |
34 | { | |
35 | ored_words[i] |= m.word[i]; | |
36 | anded_words[i] &= m.word[i]; | |
37 | } | |
38 | } | |
39 | int main () | |
40 | { | |
698be2d8 | 41 | static long double samples[5] = { 0.25L, 0.5L, 1.0L, 2.0L, 4.0L }; |
88b48903 WN |
42 | size_t j; |
43 | FILE *fp = fopen ("conftest.out", "w"); | |
44 | if (fp == NULL) | |
45 | return 1; | |
46 | for (j = 0; j < NWORDS; j++) | |
47 | anded_words[j] = ~ (unsigned int) 0; | |
698be2d8 CB |
48 | for (j = 0; j < 5; j++) |
49 | add_to_ored_words (&samples[j]); | |
88b48903 WN |
50 | /* Remove bits that are common (e.g. if representation of the first mantissa |
51 | bit is explicit). */ | |
52 | for (j = 0; j < NWORDS; j++) | |
53 | ored_words[j] &= ~anded_words[j]; | |
54 | /* Now find the nonzero word. */ | |
55 | for (j = 0; j < NWORDS; j++) | |
56 | if (ored_words[j] != 0) | |
57 | break; | |
58 | if (j < NWORDS) | |
59 | { | |
60 | size_t i; | |
61 | for (i = j + 1; i < NWORDS; i++) | |
62 | if (ored_words[i] != 0) | |
63 | { | |
64 | fprintf (fp, "unknown"); | |
65 | return (fclose (fp) != 0); | |
66 | } | |
67 | for (i = 0; ; i++) | |
68 | if ((ored_words[j] >> i) & 1) | |
69 | { | |
70 | fprintf (fp, "word %d bit %d", (int) j, (int) i); | |
71 | return (fclose (fp) != 0); | |
72 | } | |
73 | } | |
74 | fprintf (fp, "unknown"); | |
75 | return (fclose (fp) != 0); | |
76 | } | |
77 | ]])], | |
78 | [gl_cv_cc_long_double_expbit0=`cat conftest.out`], | |
79 | [gl_cv_cc_long_double_expbit0="unknown"], | |
80 | [ | |
c0c3707f | 81 | dnl When cross-compiling, in general we don't know. It depends on the |
88b48903 WN |
82 | dnl ABI and compiler version. There are too many cases. |
83 | gl_cv_cc_long_double_expbit0="unknown" | |
c0c3707f CB |
84 | case "$host_os" in |
85 | mingw*) # On native Windows (little-endian), we know the result | |
86 | # in two cases: mingw, MSVC. | |
87 | AC_EGREP_CPP([Known], [ | |
88 | #ifdef __MINGW32__ | |
89 | Known | |
90 | #endif | |
91 | ], [gl_cv_cc_long_double_expbit0="word 2 bit 0"]) | |
92 | AC_EGREP_CPP([Known], [ | |
93 | #ifdef _MSC_VER | |
94 | Known | |
95 | #endif | |
96 | ], [gl_cv_cc_long_double_expbit0="word 1 bit 20"]) | |
97 | ;; | |
98 | esac | |
88b48903 WN |
99 | ]) |
100 | rm -f conftest.out | |
101 | ]) | |
102 | case "$gl_cv_cc_long_double_expbit0" in | |
103 | word*bit*) | |
104 | word=`echo "$gl_cv_cc_long_double_expbit0" | sed -e 's/word //' -e 's/ bit.*//'` | |
105 | bit=`echo "$gl_cv_cc_long_double_expbit0" | sed -e 's/word.*bit //'` | |
106 | AC_DEFINE_UNQUOTED([LDBL_EXPBIT0_WORD], [$word], | |
107 | [Define as the word index where to find the exponent of 'long double'.]) | |
108 | AC_DEFINE_UNQUOTED([LDBL_EXPBIT0_BIT], [$bit], | |
109 | [Define as the bit index in the word where to find bit 0 of the exponent of 'long double'.]) | |
110 | ;; | |
111 | esac | |
112 | ]) |