185 lines
7.3 KiB
C
185 lines
7.3 KiB
C
/*
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* Copyright (c) 2017 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_i15_montymul(uint16_t *d, const uint16_t *x, const uint16_t *y,
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const uint16_t *m, uint16_t m0i)
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{
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size_t len, len4, u, v;
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uint32_t dh;
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len = (m[0] + 15) >> 4;
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len4 = len & ~(size_t)3;
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br_i15_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, r, zh;
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xu = x[u + 1];
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f = MUL15((d[1] + MUL15(x[u + 1], y[1])) & 0x7FFF, m0i)
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& 0x7FFF;
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#if BR_ARMEL_CORTEXM_GCC
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if (len4 != 0) {
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uint16_t *limit;
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limit = d + len4;
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asm volatile (
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"\n\
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@ carry: r=r2 \n\
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@ multipliers: xu=r3 f=r4 \n\
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@ base registers: d+v=r5 y+v=r6 m+v=r7 \n\
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@ r8 contains 0x7FFF \n\
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@ r9 contains d+len4 \n\
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ldr r0, %[limit] \n\
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ldr r3, %[xu] \n\
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mov r9, r0 \n\
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ldr r4, %[f] \n\
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eor r2, r2 \n\
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ldr r5, %[d] \n\
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sub r1, r2, #1 \n\
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ldr r6, %[y] \n\
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lsr r1, r1, #17 \n\
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ldr r7, %[m] \n\
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mov r8, r1 \n\
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loop%=: \n\
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ldrh r0, [r6, #2] \n\
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ldrh r1, [r7, #2] \n\
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mul r0, r3 \n\
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mul r1, r4 \n\
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add r2, r0, r2 \n\
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ldrh r0, [r5, #2] \n\
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add r2, r1, r2 \n\
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mov r1, r8 \n\
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add r2, r0, r2 \n\
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and r1, r2 \n\
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lsr r2, r2, #15 \n\
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strh r1, [r5, #0] \n\
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\n\
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ldrh r0, [r6, #4] \n\
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ldrh r1, [r7, #4] \n\
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mul r0, r3 \n\
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mul r1, r4 \n\
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add r2, r0, r2 \n\
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ldrh r0, [r5, #4] \n\
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add r2, r1, r2 \n\
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mov r1, r8 \n\
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add r2, r0, r2 \n\
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and r1, r2 \n\
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lsr r2, r2, #15 \n\
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strh r1, [r5, #2] \n\
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\n\
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ldrh r0, [r6, #6] \n\
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ldrh r1, [r7, #6] \n\
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mul r0, r3 \n\
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mul r1, r4 \n\
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add r2, r0, r2 \n\
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ldrh r0, [r5, #6] \n\
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add r2, r1, r2 \n\
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mov r1, r8 \n\
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add r2, r0, r2 \n\
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and r1, r2 \n\
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lsr r2, r2, #15 \n\
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strh r1, [r5, #4] \n\
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\n\
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ldrh r0, [r6, #8] \n\
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ldrh r1, [r7, #8] \n\
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mul r0, r3 \n\
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mul r1, r4 \n\
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add r2, r0, r2 \n\
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ldrh r0, [r5, #8] \n\
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add r2, r1, r2 \n\
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mov r1, r8 \n\
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add r2, r0, r2 \n\
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and r1, r2 \n\
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lsr r2, r2, #15 \n\
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strh r1, [r5, #6] \n\
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\n\
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add r5, r5, #8 \n\
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add r6, r6, #8 \n\
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add r7, r7, #8 \n\
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cmp r5, r9 \n\
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bne loop%= \n\
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\n\
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str r2, %[carry] \n\
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"
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: [carry] "=m" (r)
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: [xu] "m" (xu), [f] "m" (f), [d] "m" (d), [y] "m" (y),
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[m] "m" (m), [limit] "m" (limit)
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: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r8", "r9" );
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} else {
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r = 0;
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}
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v = len4;
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#else
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r = 0;
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for (v = 0; v < len4; v += 4) {
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uint32_t z;
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z = d[v + 1] + MUL15(xu, y[v + 1])
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+ MUL15(f, m[v + 1]) + r;
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r = z >> 15;
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d[v + 0] = z & 0x7FFF;
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z = d[v + 2] + MUL15(xu, y[v + 2])
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+ MUL15(f, m[v + 2]) + r;
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r = z >> 15;
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d[v + 1] = z & 0x7FFF;
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z = d[v + 3] + MUL15(xu, y[v + 3])
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+ MUL15(f, m[v + 3]) + r;
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r = z >> 15;
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d[v + 2] = z & 0x7FFF;
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z = d[v + 4] + MUL15(xu, y[v + 4])
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+ MUL15(f, m[v + 4]) + r;
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r = z >> 15;
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d[v + 3] = z & 0x7FFF;
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}
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#endif
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for (; v < len; v ++) {
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uint32_t z;
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z = d[v + 1] + MUL15(xu, y[v + 1])
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+ MUL15(f, m[v + 1]) + r;
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r = z >> 15;
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d[v + 0] = z & 0x7FFF;
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}
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zh = dh + r;
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d[len] = zh & 0x7FFF;
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dh = zh >> 15;
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}
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/*
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* Restore the bit length (it was overwritten in the loop above).
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*/
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d[0] = m[0];
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/*
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* d[] may be greater than m[], but it is still lower than twice
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* the modulus.
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*/
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br_i15_sub(d, m, NEQ(dh, 0) | NOT(br_i15_sub(d, m, 0)));
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}
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