annotate m4/exponentf.m4 @ 15857:6b8400199763

New module 'sqrtf'. * lib/math.in.h (sqrtf): New declaration. * lib/sqrtf.c: New file. * m4/sqrtf.m4: New file. * m4/math_h.m4 (gl_MATH_H): Test whether sqrtf is declared. (gl_MATH_H_DEFAULTS): Initialize GNULIB_SQRTF, HAVE_SQRTF. * modules/math (Makefile.am): Substitute GNULIB_SQRTF, HAVE_SQRTF. * modules/sqrtf: New file. * tests/test-math-c++.cc: Check the declaration of sqrtf. * doc/posix-functions/sqrtf.texi: Mention the new module.
author Bruno Haible <bruno@clisp.org>
date Sat, 08 Oct 2011 21:16:48 +0200
parents 97fc9a21a8fb
children 8250f2777afc
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1 # exponentf.m4 serial 2
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2 dnl Copyright (C) 2007-2008, 2010-2011 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_FLOAT_EXPONENT_LOCATION],
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7 [
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8 AC_CACHE_CHECK([where to find the exponent in a 'float'],
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9 [gl_cv_cc_float_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 (float) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
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19 typedef union { float value; unsigned int word[NWORDS]; } memory_float;
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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 (float x)
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23 {
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24 memory_float m;
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25 size_t i;
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26 /* Clear it first, in case
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27 sizeof (float) < sizeof (memory_float). */
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28 memset (&m, 0, sizeof (memory_float));
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29 m.value = x;
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30 for (i = 0; i < NWORDS; i++)
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31 {
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32 ored_words[i] |= m.word[i];
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33 anded_words[i] &= m.word[i];
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34 }
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35 }
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36 int main ()
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37 {
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38 size_t j;
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39 FILE *fp = fopen ("conftest.out", "w");
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40 if (fp == NULL)
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41 return 1;
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42 for (j = 0; j < NWORDS; j++)
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43 anded_words[j] = ~ (unsigned int) 0;
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44 add_to_ored_words (0.25f);
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45 add_to_ored_words (0.5f);
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46 add_to_ored_words (1.0f);
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47 add_to_ored_words (2.0f);
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48 add_to_ored_words (4.0f);
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49 /* Remove bits that are common (e.g. if representation of the first mantissa
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50 bit is explicit). */
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51 for (j = 0; j < NWORDS; j++)
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52 ored_words[j] &= ~anded_words[j];
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53 /* Now find the nonzero word. */
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54 for (j = 0; j < NWORDS; j++)
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55 if (ored_words[j] != 0)
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56 break;
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57 if (j < NWORDS)
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58 {
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59 size_t i;
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60 for (i = j + 1; i < NWORDS; i++)
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61 if (ored_words[i] != 0)
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62 {
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63 fprintf (fp, "unknown");
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64 return (fclose (fp) != 0);
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65 }
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66 for (i = 0; ; i++)
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67 if ((ored_words[j] >> i) & 1)
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68 {
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69 fprintf (fp, "word %d bit %d", (int) j, (int) i);
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70 return (fclose (fp) != 0);
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71 }
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72 }
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73 fprintf (fp, "unknown");
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74 return (fclose (fp) != 0);
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75 }
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76 ]])],
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77 [gl_cv_cc_float_expbit0=`cat conftest.out`],
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78 [gl_cv_cc_float_expbit0="unknown"],
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79 [gl_cv_cc_float_expbit0="word 0 bit 23"])
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80 rm -f conftest.out
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81 ])
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82 case "$gl_cv_cc_float_expbit0" in
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83 word*bit*)
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84 word=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word //' -e 's/ bit.*//'`
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85 bit=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word.*bit //'`
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86 AC_DEFINE_UNQUOTED([FLT_EXPBIT0_WORD], [$word],
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87 [Define as the word index where to find the exponent of 'float'.])
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88 AC_DEFINE_UNQUOTED([FLT_EXPBIT0_BIT], [$bit],
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89 [Define as the bit index in the word where to find bit 0 of the exponent of 'float'.])
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90 ;;
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91 esac
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92 ])