Imported gcc-4.4.3

[msp430-gcc.git] / gmp / mpf / set_q.c

diff --git a/gmp/mpf/set_q.c b/gmp/mpf/set_q.c
new file mode 100644 (file)
index 0000000..a54aa3b
--- /dev/null
+++ b/gmp/mpf/set_q.c
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+/* mpf_set_q (mpf_t rop, mpq_t op) -- Convert the rational op to the float rop.
+
+Copyright 1996, 1999, 2001, 2002, 2004, 2005 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP 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 3 of the License, or (at your
+option) any later version.
+
+The GNU MP 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 MP Library.  If not, see http://www.gnu.org/licenses/.  */
+
+#include <stdio.h>  /* for NULL */
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+/* As usual the aim is to produce PREC(r) limbs, with the high non-zero.
+   The basic mpn_tdiv_qr produces a quotient of nsize-dsize+1 limbs, with
+   either the high or second highest limb non-zero.  We arrange for
+   nsize-dsize+1 to equal prec+1, hence giving either prec or prec+1 result
+   limbs at PTR(r).
+
+   nsize-dsize+1 == prec+1 is achieved by adjusting num(q), either dropping
+   low limbs if it's too big, or padding with low zeros if it's too small.
+   The full given den(q) is always used.
+
+   We cannot truncate den(q), because even when it's much bigger than prec
+   the last limbs can still influence the final quotient.  Often they don't,
+   but we leave optimization of that to a prospective quotient-only mpn
+   division.
+
+   Not done:
+
+   If den(q) is a power of 2 then we may end up with low zero limbs on the
+   result.  But nothing is done about this, since it should be unlikely on
+   random data, and can be left to an application to call mpf_div_2exp if it
+   might occur with any frequency.
+
+   Enhancements:
+
+   The high quotient limb is non-zero when high{np,dsize} >= {dp,dsize}.  We
+   could make that comparison and use qsize==prec instead of qsize==prec+1,
+   to save one limb in the division.
+
+   Future:
+
+   If/when mpn_tdiv_qr supports its qxn parameter we can use that instead of
+   padding n with zeros in temporary space.
+
+   If/when a quotient-only division exists it can be used here immediately.
+   remp is only to satisfy mpn_tdiv_qr, the remainder is not used.  */
+
+void
+mpf_set_q (mpf_t r, mpq_srcptr q)
+{
+  mp_srcptr np, dp;
+  mp_size_t prec, nsize, dsize, qsize, prospective_qsize, tsize, zeros;
+  mp_size_t sign_quotient, high_zero;
+  mp_ptr qp, tp, remp;
+  mp_exp_t exp;
+  TMP_DECL;
+
+  ASSERT (SIZ(&q->_mp_den) > 0);  /* canonical q */
+
+  nsize = SIZ (&q->_mp_num);
+  dsize = SIZ (&q->_mp_den);
+
+  if (UNLIKELY (nsize == 0))
+    {
+      SIZ (r) = 0;
+      EXP (r) = 0;
+      return;
+    }
+
+  TMP_MARK;
+
+  prec = PREC (r);
+  qp = PTR (r);
+
+  sign_quotient = nsize;
+  nsize = ABS (nsize);
+  np = PTR (&q->_mp_num);
+  dp = PTR (&q->_mp_den);
+
+  prospective_qsize = nsize - dsize + 1;  /* q from using given n,d sizes */
+  exp = prospective_qsize;                /* ie. number of integer limbs */
+  qsize = prec + 1;                       /* desired q */
+
+  zeros = qsize - prospective_qsize;   /* n zeros to get desired qsize */
+  tsize = nsize + zeros;               /* possible copy of n */
+
+  if (WANT_TMP_DEBUG)
+    {
+      /* separate alloc blocks, for malloc debugging */
+      remp = TMP_ALLOC_LIMBS (dsize);
+      tp = NULL;
+      if (zeros > 0)
+        tp = TMP_ALLOC_LIMBS (tsize);
+    }
+  else
+    {
+      /* one alloc with a conditionalized size, for efficiency */
+      mp_size_t size = dsize + (zeros > 0 ? tsize : 0);
+      remp = TMP_ALLOC_LIMBS (size);
+      tp = remp + dsize;
+    }
+
+  if (zeros > 0)
+    {
+      /* pad n with zeros into temporary space */
+      MPN_ZERO (tp, zeros);
+      MPN_COPY (tp+zeros, np, nsize);
+      np = tp;
+      nsize = tsize;
+    }
+  else
+    {
+      /* shorten n to get desired qsize */
+      nsize += zeros;
+      np -= zeros;
+    }
+
+  ASSERT (nsize-dsize+1 == qsize);
+  mpn_tdiv_qr (qp, remp, (mp_size_t) 0, np, nsize, dp, dsize);
+
+  /* strip possible zero high limb */
+  high_zero = (qp[qsize-1] == 0);
+  qsize -= high_zero;
+  exp -= high_zero;
+
+  EXP (r) = exp;
+  SIZ (r) = sign_quotient >= 0 ? qsize : -qsize;
+
+  TMP_FREE;
+}