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diff --git a/m4/exponentf.m4 b/m4/exponentf.m4
new file mode 100644
index 0000000..7ff3413
--- /dev/null
+++ b/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
+])