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Unified Diff: gcc/gmp/mpf/div_2exp.c

Issue 3050029: [gcc] GCC 4.5.0=>4.5.1 (Closed) Base URL: ssh://git@gitrw.chromium.org:9222/nacl-toolchain.git
Patch Set: Created 10 years, 5 months ago
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Index: gcc/gmp/mpf/div_2exp.c
diff --git a/gcc/gmp/mpf/div_2exp.c b/gcc/gmp/mpf/div_2exp.c
deleted file mode 100644
index eea5de3bc88122f2a0020f109542a7bb709260c6..0000000000000000000000000000000000000000
--- a/gcc/gmp/mpf/div_2exp.c
+++ /dev/null
@@ -1,129 +0,0 @@
-/* mpf_div_2exp -- Divide a float by 2^n.
-
-Copyright 1993, 1994, 1996, 2000, 2001, 2002, 2004 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 "gmp.h"
-#include "gmp-impl.h"
-
-
-/* Multiples of GMP_NUMB_BITS in exp simply mean an amount subtracted from
- EXP(u) to set EXP(r). The remainder exp%GMP_NUMB_BITS is then a right
- shift for the limb data.
-
- If exp%GMP_NUMB_BITS == 0 then there's no shifting, we effectively just
- do an mpz_set with changed EXP(r). Like mpz_set we take prec+1 limbs in
- this case. Although just prec would suffice, it's nice to have
- mpf_div_2exp with exp==0 come out the same as mpz_set.
-
- When shifting we take up to prec many limbs from the input. Our shift is
- cy = mpn_rshift (PTR(r)+1, PTR(u)+k, ...), where k is the number of low
- limbs dropped from u, and the carry out is stored to PTR(r)[0]. We don't
- try to work extra bits from PTR(u)[k-1] (when k>=1 makes it available)
- into that low carry limb. Just prec limbs (with the high non-zero) from
- the input is enough bits for the application requested precision, no need
- to do extra work.
-
- If r==u the shift will have overlapping operands. When k>=1 (ie. when
- usize > prec), the overlap is in the style supported by rshift (ie. dst
- <= src).
-
- But when r==u and k==0 (ie. usize <= prec), we would have an invalid
- overlap (mpn_rshift (rp+1, rp, ...)). In this case we must instead use
- mpn_lshift (PTR(r), PTR(u), size, NUMB-shift). An lshift by NUMB-shift
- bits gives identical data of course, it's just its overlap restrictions
- which differ.
-
- In both shift cases, the resulting data is abs_usize+1 limbs. "adj" is
- used to add +1 to that size if the high is non-zero (it may of course
- have become zero by the shifting). EXP(u) is the exponent just above
- those abs_usize+1 limbs, so it gets -1+adj, which means -1 if the high is
- zero, or no change if the high is non-zero.
-
- Enhancements:
-
- The way mpn_lshift is used means successive mpf_div_2exp calls on the
- same operand will accumulate low zero limbs, until prec+1 limbs is
- reached. This is wasteful for subsequent operations. When abs_usize <=
- prec, we should test the low exp%GMP_NUMB_BITS many bits of PTR(u)[0],
- ie. those which would be shifted out by an mpn_rshift. If they're zero
- then use that mpn_rshift. */
-
-void
-mpf_div_2exp (mpf_ptr r, mpf_srcptr u, unsigned long int exp)
-{
- mp_srcptr up;
- mp_ptr rp = r->_mp_d;
- mp_size_t usize;
- mp_size_t abs_usize;
- mp_size_t prec = r->_mp_prec;
- mp_exp_t uexp = u->_mp_exp;
-
- usize = u->_mp_size;
-
- if (UNLIKELY (usize == 0))
- {
- r->_mp_size = 0;
- r->_mp_exp = 0;
- return;
- }
-
- abs_usize = ABS (usize);
- up = u->_mp_d;
-
- if (exp % GMP_NUMB_BITS == 0)
- {
- prec++; /* retain more precision here as we don't need
- to account for carry-out here */
- if (abs_usize > prec)
- {
- up += abs_usize - prec;
- abs_usize = prec;
- }
- if (rp != up)
- MPN_COPY_INCR (rp, up, abs_usize);
- r->_mp_exp = uexp - exp / GMP_NUMB_BITS;
- }
- else
- {
- mp_limb_t cy_limb;
- mp_size_t adj;
- if (abs_usize > prec)
- {
- up += abs_usize - prec;
- abs_usize = prec;
- /* Use mpn_rshift since mpn_lshift operates downwards, and we
- therefore would clobber part of U before using that part, in case
- R is the same variable as U. */
- cy_limb = mpn_rshift (rp + 1, up, abs_usize, exp % GMP_NUMB_BITS);
- rp[0] = cy_limb;
- adj = rp[abs_usize] != 0;
- }
- else
- {
- cy_limb = mpn_lshift (rp, up, abs_usize,
- GMP_NUMB_BITS - exp % GMP_NUMB_BITS);
- rp[abs_usize] = cy_limb;
- adj = cy_limb != 0;
- }
-
- abs_usize += adj;
- r->_mp_exp = uexp - exp / GMP_NUMB_BITS - 1 + adj;
- }
- r->_mp_size = usize >= 0 ? abs_usize : -abs_usize;
-}
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