70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
/*
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* Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "inner.h"
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/* see inner.h */
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void
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br_i32_montymul(uint32_t *d, const uint32_t *x, const uint32_t *y,
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const uint32_t *m, uint32_t m0i)
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{
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size_t len, u, v;
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uint64_t dh;
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len = (m[0] + 31) >> 5;
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br_i32_zero(d, m[0]);
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dh = 0;
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for (u = 0; u < len; u ++) {
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uint32_t f, xu;
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uint64_t r1, r2, zh;
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xu = x[u + 1];
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f = (d[1] + x[u + 1] * y[1]) * m0i;
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r1 = 0;
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r2 = 0;
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for (v = 0; v < len; v ++) {
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uint64_t z;
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uint32_t t;
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z = (uint64_t)d[v + 1] + MUL(xu, y[v + 1]) + r1;
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r1 = z >> 32;
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t = (uint32_t)z;
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z = (uint64_t)t + MUL(f, m[v + 1]) + r2;
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r2 = z >> 32;
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if (v != 0) {
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d[v] = (uint32_t)z;
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}
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}
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zh = dh + r1 + r2;
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d[len] = (uint32_t)zh;
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dh = zh >> 32;
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}
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/*
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* d[] may still be greater than m[] at that point; notably, the
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* 'dh' word may be non-zero.
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*/
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br_i32_sub(d, m, NEQ(dh, 0) | NOT(br_i32_sub(d, m, 0)));
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}
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