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authorJakub Jelinek <jakub@redhat.com>2007-07-12 18:26:36 +0000
committerJakub Jelinek <jakub@redhat.com>2007-07-12 18:26:36 +0000
commit0ecb606cb6cf65de1d9fc8a919bceb4be476c602 (patch)
tree2ea1f8305970753e4a657acb2ccc15ca3eec8e2c /sysdeps/ieee754/ldbl-128ibm/ldbl2mpn.c
parent7d58530341304d403a6626d7f7a1913165fe2f32 (diff)
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2.5-18.1
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/ldbl2mpn.c')
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diff --git a/sysdeps/ieee754/ldbl-128ibm/ldbl2mpn.c b/sysdeps/ieee754/ldbl-128ibm/ldbl2mpn.c
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index 0000000000..18a2e671ad
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+++ b/sysdeps/ieee754/ldbl-128ibm/ldbl2mpn.c
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+/* Copyright (C) 1995,1996,1997,1998,1999,2002,2003,2006
+ 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 Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; 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 <math.h>
+#include <stdlib.h>
+
+/* Convert a `long double' in IBM extended format to a multi-precision
+ integer representing the significand scaled up by its number of
+ bits (106 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 ibm_extended_long_double u;
+ unsigned long long hi, lo;
+ int ediff;
+ u.d = value;
+
+ *is_neg = u.ieee.negative;
+ *expt = (int) u.ieee.exponent - IBM_EXTENDED_LONG_DOUBLE_BIAS;
+
+ lo = ((long long) u.ieee.mantissa2 << 32) | u.ieee.mantissa3;
+ hi = ((long long) u.ieee.mantissa0 << 32) | u.ieee.mantissa1;
+ /* If the lower double is not a denomal or zero then set the hidden
+ 53rd bit. */
+ if (u.ieee.exponent2 > 0)
+ {
+ lo |= 1LL << 52;
+
+ /* The lower double is normalized separately from the upper. We may
+ need to adjust the lower manitissa to reflect this. */
+ ediff = u.ieee.exponent - u.ieee.exponent2;
+ if (ediff > 53)
+ lo = lo >> (ediff-53);
+ }
+ /* The high double may be rounded and the low double reflects the
+ difference between the long double and the rounded high double
+ value. This is indicated by a differnce between the signs of the
+ high and low doubles. */
+ if ((u.ieee.negative != u.ieee.negative2)
+ && ((u.ieee.exponent2 != 0) && (lo != 0L)))
+ {
+ lo = (1ULL << 53) - lo;
+ if (hi == 0LL)
+ {
+ /* we have a borrow from the hidden bit, so shift left 1. */
+ hi = 0x0ffffffffffffeLL | (lo >> 51);
+ lo = 0x1fffffffffffffLL & (lo << 1);
+ (*expt)--;
+ }
+ else
+ hi--;
+ }
+#if BITS_PER_MP_LIMB == 32
+ /* Combine the mantissas to be contiguous. */
+ res_ptr[0] = lo;
+ res_ptr[1] = (hi << (53 - 32)) | (lo >> 32);
+ res_ptr[2] = hi >> 11;
+ res_ptr[3] = hi >> (32 + 11);
+ #define N 4
+#elif BITS_PER_MP_LIMB == 64
+ /* Combine the two mantissas to be contiguous. */
+ res_ptr[0] = (hi << 53) | lo;
+ res_ptr[1] = hi >> 11;
+ #define N 2
+#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 \
+ - (LDBL_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[1] == 0
+ && res_ptr[N - 2] == 0 && res_ptr[N - 1] == 0) /* Assumes N<=4. */
+ /* 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 N == 2
+ if (res_ptr[N - 1] != 0)
+ {
+ count_leading_zeros (cnt, res_ptr[N - 1]);
+ cnt -= NUM_LEADING_ZEROS;
+ res_ptr[N - 1] = res_ptr[N - 1] << cnt
+ | (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt));
+ res_ptr[0] <<= cnt;
+ *expt = LDBL_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 = LDBL_MIN_EXP - 1
+ - (BITS_PER_MP_LIMB - NUM_LEADING_ZEROS) - cnt;
+ }
+#else
+ int j, k, l;
+
+ for (j = N - 1; j > 0; j--)
+ if (res_ptr[j] != 0)
+ break;
+
+ count_leading_zeros (cnt, res_ptr[j]);
+ cnt -= NUM_LEADING_ZEROS;
+ l = N - 1 - j;
+ if (cnt < 0)
+ {
+ cnt += BITS_PER_MP_LIMB;
+ l--;
+ }
+ if (!cnt)
+ for (k = N - 1; k >= l; k--)
+ res_ptr[k] = res_ptr[k-l];
+ else
+ {
+ for (k = N - 1; k > l; k--)
+ res_ptr[k] = res_ptr[k-l] << cnt
+ | res_ptr[k-l-1] >> (BITS_PER_MP_LIMB - cnt);
+ res_ptr[k--] = res_ptr[0] << cnt;
+ }
+
+ for (; k >= 0; k--)
+ res_ptr[k] = 0;
+ *expt = LDBL_MIN_EXP - 1 - l * BITS_PER_MP_LIMB - cnt;
+#endif
+ }
+ }
+ else
+ /* Add the implicit leading one bit for a normalized number. */
+ res_ptr[N - 1] |= (mp_limb_t) 1 << (LDBL_MANT_DIG - 1
+ - ((N - 1) * BITS_PER_MP_LIMB));
+
+ return N;
+}