Commit | Line | Data |
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2e65b52f | 1 | # exponentf.m4 serial 2 |
af07e104 | 2 | dnl Copyright (C) 2007-2008, 2010-2013 Free Software Foundation, Inc. |
2e65b52f LC |
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_FLOAT_EXPONENT_LOCATION], | |
7 | [ | |
8 | AC_CACHE_CHECK([where to find the exponent in a 'float'], | |
9 | [gl_cv_cc_float_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 (float) + sizeof (unsigned int) - 1) / sizeof (unsigned int)) | |
19 | typedef union { float value; unsigned int word[NWORDS]; } memory_float; | |
20 | static unsigned int ored_words[NWORDS]; | |
21 | static unsigned int anded_words[NWORDS]; | |
22 | static void add_to_ored_words (float x) | |
23 | { | |
24 | memory_float m; | |
25 | size_t i; | |
26 | /* Clear it first, in case | |
27 | sizeof (float) < sizeof (memory_float). */ | |
28 | memset (&m, 0, sizeof (memory_float)); | |
29 | m.value = x; | |
30 | for (i = 0; i < NWORDS; i++) | |
31 | { | |
32 | ored_words[i] |= m.word[i]; | |
33 | anded_words[i] &= m.word[i]; | |
34 | } | |
35 | } | |
36 | int main () | |
37 | { | |
38 | size_t j; | |
39 | FILE *fp = fopen ("conftest.out", "w"); | |
40 | if (fp == NULL) | |
41 | return 1; | |
42 | for (j = 0; j < NWORDS; j++) | |
43 | anded_words[j] = ~ (unsigned int) 0; | |
44 | add_to_ored_words (0.25f); | |
45 | add_to_ored_words (0.5f); | |
46 | add_to_ored_words (1.0f); | |
47 | add_to_ored_words (2.0f); | |
48 | add_to_ored_words (4.0f); | |
49 | /* Remove bits that are common (e.g. if representation of the first mantissa | |
50 | bit is explicit). */ | |
51 | for (j = 0; j < NWORDS; j++) | |
52 | ored_words[j] &= ~anded_words[j]; | |
53 | /* Now find the nonzero word. */ | |
54 | for (j = 0; j < NWORDS; j++) | |
55 | if (ored_words[j] != 0) | |
56 | break; | |
57 | if (j < NWORDS) | |
58 | { | |
59 | size_t i; | |
60 | for (i = j + 1; i < NWORDS; i++) | |
61 | if (ored_words[i] != 0) | |
62 | { | |
63 | fprintf (fp, "unknown"); | |
64 | return (fclose (fp) != 0); | |
65 | } | |
66 | for (i = 0; ; i++) | |
67 | if ((ored_words[j] >> i) & 1) | |
68 | { | |
69 | fprintf (fp, "word %d bit %d", (int) j, (int) i); | |
70 | return (fclose (fp) != 0); | |
71 | } | |
72 | } | |
73 | fprintf (fp, "unknown"); | |
74 | return (fclose (fp) != 0); | |
75 | } | |
76 | ]])], | |
77 | [gl_cv_cc_float_expbit0=`cat conftest.out`], | |
78 | [gl_cv_cc_float_expbit0="unknown"], | |
79 | [gl_cv_cc_float_expbit0="word 0 bit 23"]) | |
80 | rm -f conftest.out | |
81 | ]) | |
82 | case "$gl_cv_cc_float_expbit0" in | |
83 | word*bit*) | |
84 | word=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word //' -e 's/ bit.*//'` | |
85 | bit=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word.*bit //'` | |
86 | AC_DEFINE_UNQUOTED([FLT_EXPBIT0_WORD], [$word], | |
87 | [Define as the word index where to find the exponent of 'float'.]) | |
88 | AC_DEFINE_UNQUOTED([FLT_EXPBIT0_BIT], [$bit], | |
89 | [Define as the bit index in the word where to find bit 0 of the exponent of 'float'.]) | |
90 | ;; | |
91 | esac | |
92 | ]) |