1 files changed, 107 insertions, 0 deletions
diff --git a/sysdeps/ieee754/dbl2mpn.c b/sysdeps/ieee754/dbl2mpn.c
new file mode 100644
index 0000000000..6b690f711e
--- /dev/null
+++ b/sysdeps/ieee754/dbl2mpn.c
@@ -0,0 +1,107 @@
+/* Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+#include "ieee754.h"
+#include <float.h>
+#include <stdlib.h>
+
+/* Convert a `double' in IEEE754 standard double-precision format to a
+   multi-precision integer representing the significand scaled up by its
+   number of bits (52 for double) and an integral power of two (MPN frexp). */
+
+mp_size_t
+__mpn_extract_double (mp_ptr res_ptr, mp_size_t size,
+		      int *expt, int *is_neg,
+		      double value)
+{
+  union ieee754_double u;
+  u.d = value;
+
+  *is_neg = u.ieee.negative;
+  *expt = (int) u.ieee.exponent - IEEE754_DOUBLE_BIAS;
+
+#if BITS_PER_MP_LIMB == 32
+  res_ptr[0] = u.ieee.mantissa1; /* Low-order 32 bits of fraction.  */
+  res_ptr[1] = u.ieee.mantissa0; /* High-order 20 bits.  */
+  #define N 2
+#elif BITS_PER_MP_LIMB == 64
+  /* Hopefully the compiler will combine the two bitfield extracts
+     and this composition into just the original quadword extract.  */
+  res_ptr[0] = (u.ieee.mantissa0 << 32) | u.ieee.mantissa1;
+  #define N 1
+#else
+  #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
+#endif
+/* The format does not fill the last limb.  There are some zeros.  */
+#define NUM_LEADING_ZEROS (BITS_PER_MP_LIMB \
+			   - (DBL_MANT_DIG - ((N - 1) * BITS_PER_MP_LIMB)))
+
+  if (u.ieee.exponent == 0)
+    {
+      /* A biased exponent of zero is a special case.
+	 Either it is a zero or it is a denormal number.  */
+      if (res_ptr[0] == 0 && res_ptr[N - 1] == 0) /* Assumes N<=2.  */
+	/* It's zero.  */
+	*expt = 0;
+      else
+	{
+          /* It is a denormal number, meaning it has no implicit leading
+	     one bit, and its exponent is in fact the format minimum.  */
+	  int cnt;
+
+	  if (res_ptr[N - 1] != 0)
+	    {
+	      count_leading_zeros (cnt, res_ptr[N - 1]);
+	      cnt -= NUM_LEADING_ZEROS;
+#if N == 2
+	      res_ptr[N - 1] = res_ptr[1] << cnt
+			       | (N - 1)
+			         * (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt));
+	      res_ptr[0] <<= cnt;
+#else
+	      res_ptr[N - 1] <<= cnt;
+#endif
+	      *expt = DBL_MIN_EXP - 1 - cnt;
+	    }
+	  else
+	    {
+	      count_leading_zeros (cnt, res_ptr[0]);
+	      if (cnt >= NUM_LEADING_ZEROS)
+		{
+		  res_ptr[N - 1] = res_ptr[0] << (cnt - NUM_LEADING_ZEROS);
+		  res_ptr[0] = 0; 
+		}
+	      else
+		{
+		  res_ptr[N - 1] = res_ptr[0] >> (NUM_LEADING_ZEROS - cnt);
+		  res_ptr[0] <<= BITS_PER_MP_LIMB - (NUM_LEADING_ZEROS - cnt);
+		}
+	      *expt = DBL_MIN_EXP - 1
+		      - (BITS_PER_MP_LIMB - NUM_LEADING_ZEROS) - cnt;
+	    }
+	}
+    }
+  else
+    /* Add the implicit leading one bit for a normalized number.  */
+    res_ptr[N - 1] |= 1 << (DBL_MANT_DIG - 1 - ((N - 1) * BITS_PER_MP_LIMB));
+
+  return N;
+}