forked from luck/tmp_suning_uos_patched
ae6ee6ae2b
This patch removes a number of unused variables and marks others
as unused in order to silence compiler warnings about them.
Fixes: a8ea8bdd9d ("lib/mpi: Extend the MPI library")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
518 lines
13 KiB
C
518 lines
13 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/* mpihelp-div.c - MPI helper functions
|
|
* Copyright (C) 1994, 1996 Free Software Foundation, Inc.
|
|
* Copyright (C) 1998, 1999 Free Software Foundation, Inc.
|
|
*
|
|
* This file is part of GnuPG.
|
|
*
|
|
* Note: This code is heavily based on the GNU MP Library.
|
|
* Actually it's the same code with only minor changes in the
|
|
* way the data is stored; this is to support the abstraction
|
|
* of an optional secure memory allocation which may be used
|
|
* to avoid revealing of sensitive data due to paging etc.
|
|
* The GNU MP Library itself is published under the LGPL;
|
|
* however I decided to publish this code under the plain GPL.
|
|
*/
|
|
|
|
#include "mpi-internal.h"
|
|
#include "longlong.h"
|
|
|
|
#ifndef UMUL_TIME
|
|
#define UMUL_TIME 1
|
|
#endif
|
|
#ifndef UDIV_TIME
|
|
#define UDIV_TIME UMUL_TIME
|
|
#endif
|
|
|
|
|
|
mpi_limb_t
|
|
mpihelp_mod_1(mpi_ptr_t dividend_ptr, mpi_size_t dividend_size,
|
|
mpi_limb_t divisor_limb)
|
|
{
|
|
mpi_size_t i;
|
|
mpi_limb_t n1, n0, r;
|
|
mpi_limb_t dummy __maybe_unused;
|
|
|
|
/* Botch: Should this be handled at all? Rely on callers? */
|
|
if (!dividend_size)
|
|
return 0;
|
|
|
|
/* If multiplication is much faster than division, and the
|
|
* dividend is large, pre-invert the divisor, and use
|
|
* only multiplications in the inner loop.
|
|
*
|
|
* This test should be read:
|
|
* Does it ever help to use udiv_qrnnd_preinv?
|
|
* && Does what we save compensate for the inversion overhead?
|
|
*/
|
|
if (UDIV_TIME > (2 * UMUL_TIME + 6)
|
|
&& (UDIV_TIME - (2 * UMUL_TIME + 6)) * dividend_size > UDIV_TIME) {
|
|
int normalization_steps;
|
|
|
|
normalization_steps = count_leading_zeros(divisor_limb);
|
|
if (normalization_steps) {
|
|
mpi_limb_t divisor_limb_inverted;
|
|
|
|
divisor_limb <<= normalization_steps;
|
|
|
|
/* Compute (2**2N - 2**N * DIVISOR_LIMB) / DIVISOR_LIMB. The
|
|
* result is a (N+1)-bit approximation to 1/DIVISOR_LIMB, with the
|
|
* most significant bit (with weight 2**N) implicit.
|
|
*
|
|
* Special case for DIVISOR_LIMB == 100...000.
|
|
*/
|
|
if (!(divisor_limb << 1))
|
|
divisor_limb_inverted = ~(mpi_limb_t)0;
|
|
else
|
|
udiv_qrnnd(divisor_limb_inverted, dummy,
|
|
-divisor_limb, 0, divisor_limb);
|
|
|
|
n1 = dividend_ptr[dividend_size - 1];
|
|
r = n1 >> (BITS_PER_MPI_LIMB - normalization_steps);
|
|
|
|
/* Possible optimization:
|
|
* if (r == 0
|
|
* && divisor_limb > ((n1 << normalization_steps)
|
|
* | (dividend_ptr[dividend_size - 2] >> ...)))
|
|
* ...one division less...
|
|
*/
|
|
for (i = dividend_size - 2; i >= 0; i--) {
|
|
n0 = dividend_ptr[i];
|
|
UDIV_QRNND_PREINV(dummy, r, r,
|
|
((n1 << normalization_steps)
|
|
| (n0 >> (BITS_PER_MPI_LIMB - normalization_steps))),
|
|
divisor_limb, divisor_limb_inverted);
|
|
n1 = n0;
|
|
}
|
|
UDIV_QRNND_PREINV(dummy, r, r,
|
|
n1 << normalization_steps,
|
|
divisor_limb, divisor_limb_inverted);
|
|
return r >> normalization_steps;
|
|
} else {
|
|
mpi_limb_t divisor_limb_inverted;
|
|
|
|
/* Compute (2**2N - 2**N * DIVISOR_LIMB) / DIVISOR_LIMB. The
|
|
* result is a (N+1)-bit approximation to 1/DIVISOR_LIMB, with the
|
|
* most significant bit (with weight 2**N) implicit.
|
|
*
|
|
* Special case for DIVISOR_LIMB == 100...000.
|
|
*/
|
|
if (!(divisor_limb << 1))
|
|
divisor_limb_inverted = ~(mpi_limb_t)0;
|
|
else
|
|
udiv_qrnnd(divisor_limb_inverted, dummy,
|
|
-divisor_limb, 0, divisor_limb);
|
|
|
|
i = dividend_size - 1;
|
|
r = dividend_ptr[i];
|
|
|
|
if (r >= divisor_limb)
|
|
r = 0;
|
|
else
|
|
i--;
|
|
|
|
for ( ; i >= 0; i--) {
|
|
n0 = dividend_ptr[i];
|
|
UDIV_QRNND_PREINV(dummy, r, r,
|
|
n0, divisor_limb, divisor_limb_inverted);
|
|
}
|
|
return r;
|
|
}
|
|
} else {
|
|
if (UDIV_NEEDS_NORMALIZATION) {
|
|
int normalization_steps;
|
|
|
|
normalization_steps = count_leading_zeros(divisor_limb);
|
|
if (normalization_steps) {
|
|
divisor_limb <<= normalization_steps;
|
|
|
|
n1 = dividend_ptr[dividend_size - 1];
|
|
r = n1 >> (BITS_PER_MPI_LIMB - normalization_steps);
|
|
|
|
/* Possible optimization:
|
|
* if (r == 0
|
|
* && divisor_limb > ((n1 << normalization_steps)
|
|
* | (dividend_ptr[dividend_size - 2] >> ...)))
|
|
* ...one division less...
|
|
*/
|
|
for (i = dividend_size - 2; i >= 0; i--) {
|
|
n0 = dividend_ptr[i];
|
|
udiv_qrnnd(dummy, r, r,
|
|
((n1 << normalization_steps)
|
|
| (n0 >> (BITS_PER_MPI_LIMB - normalization_steps))),
|
|
divisor_limb);
|
|
n1 = n0;
|
|
}
|
|
udiv_qrnnd(dummy, r, r,
|
|
n1 << normalization_steps,
|
|
divisor_limb);
|
|
return r >> normalization_steps;
|
|
}
|
|
}
|
|
/* No normalization needed, either because udiv_qrnnd doesn't require
|
|
* it, or because DIVISOR_LIMB is already normalized.
|
|
*/
|
|
i = dividend_size - 1;
|
|
r = dividend_ptr[i];
|
|
|
|
if (r >= divisor_limb)
|
|
r = 0;
|
|
else
|
|
i--;
|
|
|
|
for (; i >= 0; i--) {
|
|
n0 = dividend_ptr[i];
|
|
udiv_qrnnd(dummy, r, r, n0, divisor_limb);
|
|
}
|
|
return r;
|
|
}
|
|
}
|
|
|
|
/* Divide num (NP/NSIZE) by den (DP/DSIZE) and write
|
|
* the NSIZE-DSIZE least significant quotient limbs at QP
|
|
* and the DSIZE long remainder at NP. If QEXTRA_LIMBS is
|
|
* non-zero, generate that many fraction bits and append them after the
|
|
* other quotient limbs.
|
|
* Return the most significant limb of the quotient, this is always 0 or 1.
|
|
*
|
|
* Preconditions:
|
|
* 0. NSIZE >= DSIZE.
|
|
* 1. The most significant bit of the divisor must be set.
|
|
* 2. QP must either not overlap with the input operands at all, or
|
|
* QP + DSIZE >= NP must hold true. (This means that it's
|
|
* possible to put the quotient in the high part of NUM, right after the
|
|
* remainder in NUM.
|
|
* 3. NSIZE >= DSIZE, even if QEXTRA_LIMBS is non-zero.
|
|
*/
|
|
|
|
mpi_limb_t
|
|
mpihelp_divrem(mpi_ptr_t qp, mpi_size_t qextra_limbs,
|
|
mpi_ptr_t np, mpi_size_t nsize, mpi_ptr_t dp, mpi_size_t dsize)
|
|
{
|
|
mpi_limb_t most_significant_q_limb = 0;
|
|
|
|
switch (dsize) {
|
|
case 0:
|
|
/* We are asked to divide by zero, so go ahead and do it! (To make
|
|
the compiler not remove this statement, return the value.) */
|
|
/*
|
|
* existing clients of this function have been modified
|
|
* not to call it with dsize == 0, so this should not happen
|
|
*/
|
|
return 1 / dsize;
|
|
|
|
case 1:
|
|
{
|
|
mpi_size_t i;
|
|
mpi_limb_t n1;
|
|
mpi_limb_t d;
|
|
|
|
d = dp[0];
|
|
n1 = np[nsize - 1];
|
|
|
|
if (n1 >= d) {
|
|
n1 -= d;
|
|
most_significant_q_limb = 1;
|
|
}
|
|
|
|
qp += qextra_limbs;
|
|
for (i = nsize - 2; i >= 0; i--)
|
|
udiv_qrnnd(qp[i], n1, n1, np[i], d);
|
|
qp -= qextra_limbs;
|
|
|
|
for (i = qextra_limbs - 1; i >= 0; i--)
|
|
udiv_qrnnd(qp[i], n1, n1, 0, d);
|
|
|
|
np[0] = n1;
|
|
}
|
|
break;
|
|
|
|
case 2:
|
|
{
|
|
mpi_size_t i;
|
|
mpi_limb_t n1, n0, n2;
|
|
mpi_limb_t d1, d0;
|
|
|
|
np += nsize - 2;
|
|
d1 = dp[1];
|
|
d0 = dp[0];
|
|
n1 = np[1];
|
|
n0 = np[0];
|
|
|
|
if (n1 >= d1 && (n1 > d1 || n0 >= d0)) {
|
|
sub_ddmmss(n1, n0, n1, n0, d1, d0);
|
|
most_significant_q_limb = 1;
|
|
}
|
|
|
|
for (i = qextra_limbs + nsize - 2 - 1; i >= 0; i--) {
|
|
mpi_limb_t q;
|
|
mpi_limb_t r;
|
|
|
|
if (i >= qextra_limbs)
|
|
np--;
|
|
else
|
|
np[0] = 0;
|
|
|
|
if (n1 == d1) {
|
|
/* Q should be either 111..111 or 111..110. Need special
|
|
* treatment of this rare case as normal division would
|
|
* give overflow. */
|
|
q = ~(mpi_limb_t) 0;
|
|
|
|
r = n0 + d1;
|
|
if (r < d1) { /* Carry in the addition? */
|
|
add_ssaaaa(n1, n0, r - d0,
|
|
np[0], 0, d0);
|
|
qp[i] = q;
|
|
continue;
|
|
}
|
|
n1 = d0 - (d0 != 0 ? 1 : 0);
|
|
n0 = -d0;
|
|
} else {
|
|
udiv_qrnnd(q, r, n1, n0, d1);
|
|
umul_ppmm(n1, n0, d0, q);
|
|
}
|
|
|
|
n2 = np[0];
|
|
q_test:
|
|
if (n1 > r || (n1 == r && n0 > n2)) {
|
|
/* The estimated Q was too large. */
|
|
q--;
|
|
sub_ddmmss(n1, n0, n1, n0, 0, d0);
|
|
r += d1;
|
|
if (r >= d1) /* If not carry, test Q again. */
|
|
goto q_test;
|
|
}
|
|
|
|
qp[i] = q;
|
|
sub_ddmmss(n1, n0, r, n2, n1, n0);
|
|
}
|
|
np[1] = n1;
|
|
np[0] = n0;
|
|
}
|
|
break;
|
|
|
|
default:
|
|
{
|
|
mpi_size_t i;
|
|
mpi_limb_t dX, d1, n0;
|
|
|
|
np += nsize - dsize;
|
|
dX = dp[dsize - 1];
|
|
d1 = dp[dsize - 2];
|
|
n0 = np[dsize - 1];
|
|
|
|
if (n0 >= dX) {
|
|
if (n0 > dX
|
|
|| mpihelp_cmp(np, dp, dsize - 1) >= 0) {
|
|
mpihelp_sub_n(np, np, dp, dsize);
|
|
n0 = np[dsize - 1];
|
|
most_significant_q_limb = 1;
|
|
}
|
|
}
|
|
|
|
for (i = qextra_limbs + nsize - dsize - 1; i >= 0; i--) {
|
|
mpi_limb_t q;
|
|
mpi_limb_t n1, n2;
|
|
mpi_limb_t cy_limb;
|
|
|
|
if (i >= qextra_limbs) {
|
|
np--;
|
|
n2 = np[dsize];
|
|
} else {
|
|
n2 = np[dsize - 1];
|
|
MPN_COPY_DECR(np + 1, np, dsize - 1);
|
|
np[0] = 0;
|
|
}
|
|
|
|
if (n0 == dX) {
|
|
/* This might over-estimate q, but it's probably not worth
|
|
* the extra code here to find out. */
|
|
q = ~(mpi_limb_t) 0;
|
|
} else {
|
|
mpi_limb_t r;
|
|
|
|
udiv_qrnnd(q, r, n0, np[dsize - 1], dX);
|
|
umul_ppmm(n1, n0, d1, q);
|
|
|
|
while (n1 > r
|
|
|| (n1 == r
|
|
&& n0 > np[dsize - 2])) {
|
|
q--;
|
|
r += dX;
|
|
if (r < dX) /* I.e. "carry in previous addition?" */
|
|
break;
|
|
n1 -= n0 < d1;
|
|
n0 -= d1;
|
|
}
|
|
}
|
|
|
|
/* Possible optimization: We already have (q * n0) and (1 * n1)
|
|
* after the calculation of q. Taking advantage of that, we
|
|
* could make this loop make two iterations less. */
|
|
cy_limb = mpihelp_submul_1(np, dp, dsize, q);
|
|
|
|
if (n2 != cy_limb) {
|
|
mpihelp_add_n(np, np, dp, dsize);
|
|
q--;
|
|
}
|
|
|
|
qp[i] = q;
|
|
n0 = np[dsize - 1];
|
|
}
|
|
}
|
|
}
|
|
|
|
return most_significant_q_limb;
|
|
}
|
|
|
|
/****************
|
|
* Divide (DIVIDEND_PTR,,DIVIDEND_SIZE) by DIVISOR_LIMB.
|
|
* Write DIVIDEND_SIZE limbs of quotient at QUOT_PTR.
|
|
* Return the single-limb remainder.
|
|
* There are no constraints on the value of the divisor.
|
|
*
|
|
* QUOT_PTR and DIVIDEND_PTR might point to the same limb.
|
|
*/
|
|
|
|
mpi_limb_t
|
|
mpihelp_divmod_1(mpi_ptr_t quot_ptr,
|
|
mpi_ptr_t dividend_ptr, mpi_size_t dividend_size,
|
|
mpi_limb_t divisor_limb)
|
|
{
|
|
mpi_size_t i;
|
|
mpi_limb_t n1, n0, r;
|
|
mpi_limb_t dummy __maybe_unused;
|
|
|
|
if (!dividend_size)
|
|
return 0;
|
|
|
|
/* If multiplication is much faster than division, and the
|
|
* dividend is large, pre-invert the divisor, and use
|
|
* only multiplications in the inner loop.
|
|
*
|
|
* This test should be read:
|
|
* Does it ever help to use udiv_qrnnd_preinv?
|
|
* && Does what we save compensate for the inversion overhead?
|
|
*/
|
|
if (UDIV_TIME > (2 * UMUL_TIME + 6)
|
|
&& (UDIV_TIME - (2 * UMUL_TIME + 6)) * dividend_size > UDIV_TIME) {
|
|
int normalization_steps;
|
|
|
|
normalization_steps = count_leading_zeros(divisor_limb);
|
|
if (normalization_steps) {
|
|
mpi_limb_t divisor_limb_inverted;
|
|
|
|
divisor_limb <<= normalization_steps;
|
|
|
|
/* Compute (2**2N - 2**N * DIVISOR_LIMB) / DIVISOR_LIMB. The
|
|
* result is a (N+1)-bit approximation to 1/DIVISOR_LIMB, with the
|
|
* most significant bit (with weight 2**N) implicit.
|
|
*/
|
|
/* Special case for DIVISOR_LIMB == 100...000. */
|
|
if (!(divisor_limb << 1))
|
|
divisor_limb_inverted = ~(mpi_limb_t)0;
|
|
else
|
|
udiv_qrnnd(divisor_limb_inverted, dummy,
|
|
-divisor_limb, 0, divisor_limb);
|
|
|
|
n1 = dividend_ptr[dividend_size - 1];
|
|
r = n1 >> (BITS_PER_MPI_LIMB - normalization_steps);
|
|
|
|
/* Possible optimization:
|
|
* if (r == 0
|
|
* && divisor_limb > ((n1 << normalization_steps)
|
|
* | (dividend_ptr[dividend_size - 2] >> ...)))
|
|
* ...one division less...
|
|
*/
|
|
for (i = dividend_size - 2; i >= 0; i--) {
|
|
n0 = dividend_ptr[i];
|
|
UDIV_QRNND_PREINV(quot_ptr[i + 1], r, r,
|
|
((n1 << normalization_steps)
|
|
| (n0 >> (BITS_PER_MPI_LIMB - normalization_steps))),
|
|
divisor_limb, divisor_limb_inverted);
|
|
n1 = n0;
|
|
}
|
|
UDIV_QRNND_PREINV(quot_ptr[0], r, r,
|
|
n1 << normalization_steps,
|
|
divisor_limb, divisor_limb_inverted);
|
|
return r >> normalization_steps;
|
|
} else {
|
|
mpi_limb_t divisor_limb_inverted;
|
|
|
|
/* Compute (2**2N - 2**N * DIVISOR_LIMB) / DIVISOR_LIMB. The
|
|
* result is a (N+1)-bit approximation to 1/DIVISOR_LIMB, with the
|
|
* most significant bit (with weight 2**N) implicit.
|
|
*/
|
|
/* Special case for DIVISOR_LIMB == 100...000. */
|
|
if (!(divisor_limb << 1))
|
|
divisor_limb_inverted = ~(mpi_limb_t) 0;
|
|
else
|
|
udiv_qrnnd(divisor_limb_inverted, dummy,
|
|
-divisor_limb, 0, divisor_limb);
|
|
|
|
i = dividend_size - 1;
|
|
r = dividend_ptr[i];
|
|
|
|
if (r >= divisor_limb)
|
|
r = 0;
|
|
else
|
|
quot_ptr[i--] = 0;
|
|
|
|
for ( ; i >= 0; i--) {
|
|
n0 = dividend_ptr[i];
|
|
UDIV_QRNND_PREINV(quot_ptr[i], r, r,
|
|
n0, divisor_limb, divisor_limb_inverted);
|
|
}
|
|
return r;
|
|
}
|
|
} else {
|
|
if (UDIV_NEEDS_NORMALIZATION) {
|
|
int normalization_steps;
|
|
|
|
normalization_steps = count_leading_zeros(divisor_limb);
|
|
if (normalization_steps) {
|
|
divisor_limb <<= normalization_steps;
|
|
|
|
n1 = dividend_ptr[dividend_size - 1];
|
|
r = n1 >> (BITS_PER_MPI_LIMB - normalization_steps);
|
|
|
|
/* Possible optimization:
|
|
* if (r == 0
|
|
* && divisor_limb > ((n1 << normalization_steps)
|
|
* | (dividend_ptr[dividend_size - 2] >> ...)))
|
|
* ...one division less...
|
|
*/
|
|
for (i = dividend_size - 2; i >= 0; i--) {
|
|
n0 = dividend_ptr[i];
|
|
udiv_qrnnd(quot_ptr[i + 1], r, r,
|
|
((n1 << normalization_steps)
|
|
| (n0 >> (BITS_PER_MPI_LIMB - normalization_steps))),
|
|
divisor_limb);
|
|
n1 = n0;
|
|
}
|
|
udiv_qrnnd(quot_ptr[0], r, r,
|
|
n1 << normalization_steps,
|
|
divisor_limb);
|
|
return r >> normalization_steps;
|
|
}
|
|
}
|
|
/* No normalization needed, either because udiv_qrnnd doesn't require
|
|
* it, or because DIVISOR_LIMB is already normalized.
|
|
*/
|
|
i = dividend_size - 1;
|
|
r = dividend_ptr[i];
|
|
|
|
if (r >= divisor_limb)
|
|
r = 0;
|
|
else
|
|
quot_ptr[i--] = 0;
|
|
|
|
for (; i >= 0; i--) {
|
|
n0 = dividend_ptr[i];
|
|
udiv_qrnnd(quot_ptr[i], r, r, n0, divisor_limb);
|
|
}
|
|
return r;
|
|
}
|
|
}
|