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-rw-r--r--gnulib_m4/exponentl.m4112
1 files changed, 112 insertions, 0 deletions
diff --git a/gnulib_m4/exponentl.m4 b/gnulib_m4/exponentl.m4
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+# exponentl.m4 serial 5
+dnl Copyright (C) 2007-2023 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_LONG_DOUBLE_EXPONENT_LOCATION],
+[
+ AC_REQUIRE([gl_BIGENDIAN])
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CACHE_CHECK([where to find the exponent in a 'long double'],
+ [gl_cv_cc_long_double_expbit0],
+ [
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#include <float.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#define NWORDS \
+ ((sizeof (long double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
+typedef union { long double value; unsigned int word[NWORDS]; }
+ memory_long_double;
+static unsigned int ored_words[NWORDS];
+static unsigned int anded_words[NWORDS];
+static void add_to_ored_words (long double *x)
+{
+ memory_long_double m;
+ size_t i;
+ /* Clear it first, in case
+ sizeof (long double) < sizeof (memory_long_double). */
+ memset (&m, 0, sizeof (memory_long_double));
+ m.value = *x;
+ for (i = 0; i < NWORDS; i++)
+ {
+ ored_words[i] |= m.word[i];
+ anded_words[i] &= m.word[i];
+ }
+}
+int main ()
+{
+ static long double samples[5] = { 0.25L, 0.5L, 1.0L, 2.0L, 4.0L };
+ 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;
+ for (j = 0; j < 5; j++)
+ add_to_ored_words (&samples[j]);
+ /* 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_long_double_expbit0=`cat conftest.out`],
+ [gl_cv_cc_long_double_expbit0="unknown"],
+ [
+ dnl When cross-compiling, in general we don't know. It depends on the
+ dnl ABI and compiler version. There are too many cases.
+ gl_cv_cc_long_double_expbit0="unknown"
+ case "$host_os" in
+ mingw*) # On native Windows (little-endian), we know the result
+ # in two cases: mingw, MSVC.
+ AC_EGREP_CPP([Known], [
+#ifdef __MINGW32__
+ Known
+#endif
+ ], [gl_cv_cc_long_double_expbit0="word 2 bit 0"])
+ AC_EGREP_CPP([Known], [
+#ifdef _MSC_VER
+ Known
+#endif
+ ], [gl_cv_cc_long_double_expbit0="word 1 bit 20"])
+ ;;
+ esac
+ ])
+ rm -f conftest.out
+ ])
+ case "$gl_cv_cc_long_double_expbit0" in
+ word*bit*)
+ word=`echo "$gl_cv_cc_long_double_expbit0" | sed -e 's/word //' -e 's/ bit.*//'`
+ bit=`echo "$gl_cv_cc_long_double_expbit0" | sed -e 's/word.*bit //'`
+ AC_DEFINE_UNQUOTED([LDBL_EXPBIT0_WORD], [$word],
+ [Define as the word index where to find the exponent of 'long double'.])
+ AC_DEFINE_UNQUOTED([LDBL_EXPBIT0_BIT], [$bit],
+ [Define as the bit index in the word where to find bit 0 of the exponent of 'long double'.])
+ ;;
+ esac
+])