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-rw-r--r--sysdeps/ieee754/dbl-64/dbl2mpn.c107
1 files changed, 107 insertions, 0 deletions
diff --git a/sysdeps/ieee754/dbl-64/dbl2mpn.c b/sysdeps/ieee754/dbl-64/dbl2mpn.c
new file mode 100644
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+++ b/sysdeps/ieee754/dbl-64/dbl2mpn.c
@@ -0,0 +1,107 @@
+/* Copyright (C) 1993, 1994, 1995, 1996, 1997 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., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, 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] = ((unsigned long int) 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] |= 1L << (DBL_MANT_DIG - 1 - ((N - 1) * BITS_PER_MP_LIMB));
+
+ return N;
+}