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authorAndreas Rottmann <a.rottmann@gmx.at>2009-09-14 12:32:44 +0200
committerAndreas Rottmann <a.rottmann@gmx.at>2009-09-14 12:32:44 +0200
commitfa095a4504cbe668e4244547e2c141597bea4ecf (patch)
tree06135820a286ffec47804e75fbf8a147e92acd2e /gnulib-m4/exponentf.m4
Imported Upstream version 0.9.1upstream/0.9.1
Diffstat (limited to 'gnulib-m4/exponentf.m4')
-rw-r--r--gnulib-m4/exponentf.m491
1 files changed, 91 insertions, 0 deletions
diff --git a/gnulib-m4/exponentf.m4 b/gnulib-m4/exponentf.m4
new file mode 100644
index 00000000..7ff34131
--- /dev/null
+++ b/gnulib-m4/exponentf.m4
@@ -0,0 +1,91 @@
+# exponentf.m4 serial 1
+dnl Copyright (C) 2007-2008 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+AC_DEFUN([gl_FLOAT_EXPONENT_LOCATION],
+[
+ AC_CACHE_CHECK([where to find the exponent in a 'float'],
+ [gl_cv_cc_float_expbit0],
+ [
+ AC_TRY_RUN([
+#include <float.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#define NWORDS \
+ ((sizeof (float) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
+typedef union { float value; unsigned int word[NWORDS]; } memory_float;
+static unsigned int ored_words[NWORDS];
+static unsigned int anded_words[NWORDS];
+static void add_to_ored_words (float x)
+{
+ memory_float m;
+ size_t i;
+ /* Clear it first, in case
+ sizeof (float) < sizeof (memory_float). */
+ memset (&m, 0, sizeof (memory_float));
+ m.value = x;
+ for (i = 0; i < NWORDS; i++)
+ {
+ ored_words[i] |= m.word[i];
+ anded_words[i] &= m.word[i];
+ }
+}
+int main ()
+{
+ size_t j;
+ FILE *fp = fopen ("conftest.out", "w");
+ if (fp == NULL)
+ return 1;
+ for (j = 0; j < NWORDS; j++)
+ anded_words[j] = ~ (unsigned int) 0;
+ add_to_ored_words (0.25f);
+ add_to_ored_words (0.5f);
+ add_to_ored_words (1.0f);
+ add_to_ored_words (2.0f);
+ add_to_ored_words (4.0f);
+ /* Remove bits that are common (e.g. if representation of the first mantissa
+ bit is explicit). */
+ for (j = 0; j < NWORDS; j++)
+ ored_words[j] &= ~anded_words[j];
+ /* Now find the nonzero word. */
+ for (j = 0; j < NWORDS; j++)
+ if (ored_words[j] != 0)
+ break;
+ if (j < NWORDS)
+ {
+ size_t i;
+ for (i = j + 1; i < NWORDS; i++)
+ if (ored_words[i] != 0)
+ {
+ fprintf (fp, "unknown");
+ return (fclose (fp) != 0);
+ }
+ for (i = 0; ; i++)
+ if ((ored_words[j] >> i) & 1)
+ {
+ fprintf (fp, "word %d bit %d", (int) j, (int) i);
+ return (fclose (fp) != 0);
+ }
+ }
+ fprintf (fp, "unknown");
+ return (fclose (fp) != 0);
+}
+ ],
+ [gl_cv_cc_float_expbit0=`cat conftest.out`],
+ [gl_cv_cc_float_expbit0="unknown"],
+ [gl_cv_cc_float_expbit0="word 0 bit 23"])
+ rm -f conftest.out
+ ])
+ case "$gl_cv_cc_float_expbit0" in
+ word*bit*)
+ word=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word //' -e 's/ bit.*//'`
+ bit=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word.*bit //'`
+ AC_DEFINE_UNQUOTED([FLT_EXPBIT0_WORD], [$word],
+ [Define as the word index where to find the exponent of 'float'.])
+ AC_DEFINE_UNQUOTED([FLT_EXPBIT0_BIT], [$bit],
+ [Define as the bit index in the word where to find bit 0 of the exponent of 'float'.])
+ ;;
+ esac
+])