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-rw-r--r--sysdeps/ieee754/ldbl2mpn.c93
1 files changed, 93 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl2mpn.c b/sysdeps/ieee754/ldbl2mpn.c
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+/* Copyright (C) 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 `long double' in IEEE854 standard double-precision format to a
+ multi-precision integer representing the significand scaled up by its
+ number of bits (64 for long double) and an integral power of two
+ (MPN frexpl). */
+
+mp_size_t
+__mpn_extract_long_double (mp_ptr res_ptr, mp_size_t size,
+ int *expt, int *is_neg,
+ long double value)
+{
+ union ieee854_long_double u;
+ u.d = value;
+
+ *is_neg = u.ieee.negative;
+ *expt = (int) u.ieee.exponent - IEEE854_LONG_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 32 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
+
+ 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]);
+ if (cnt != 0)
+ {
+#if N == 2
+ res_ptr[N - 1] = res_ptr[N - 1] << cnt
+ | (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt));
+ res_ptr[0] <<= cnt;
+#else
+ res_ptr[N - 1] <<= cnt;
+#endif
+ }
+ *expt = LDBL_MIN_EXP - 2 - cnt;
+ }
+ else
+ {
+ count_leading_zeros (cnt, res_ptr[0]);
+ res_ptr[N - 1] = res_ptr[0] << cnt;
+ res_ptr[0] = 0;
+ *expt = LDBL_MIN_EXP - 2 - BITS_PER_MP_LIMB - cnt;
+ }
+ }
+ }
+
+ return N;
+}