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/*
* Copyright (c) 2017 Thomas Pornin <[email protected]>
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "inner.h"
/* see inner.h */
void
br_i15_montymul(uint16_t *d, const uint16_t *x, const uint16_t *y,
const uint16_t *m, uint16_t m0i)
{
size_t len, len4, u, v;
uint32_t dh;
len = (m[0] + 15) >> 4;
len4 = len & ~(size_t)3;
br_i15_zero(d, m[0]);
dh = 0;
for (u = 0; u < len; u ++) {
uint32_t f, xu, r, zh;
xu = x[u + 1];
f = MUL15((d[1] + MUL15(x[u + 1], y[1])) & 0x7FFF, m0i)
& 0x7FFF;
#if BR_ARMEL_CORTEXM_GCC
if (len4 != 0) {
uint16_t *limit;
limit = d + len4;
asm volatile (
"\n\
@ carry: r=r2 \n\
@ multipliers: xu=r3 f=r4 \n\
@ base registers: d+v=r5 y+v=r6 m+v=r7 \n\
@ r8 contains 0x7FFF \n\
@ r9 contains d+len4 \n\
ldr r0, %[limit] \n\
ldr r3, %[xu] \n\
mov r9, r0 \n\
ldr r4, %[f] \n\
eor r2, r2 \n\
ldr r5, %[d] \n\
sub r1, r2, #1 \n\
ldr r6, %[y] \n\
lsr r1, r1, #17 \n\
ldr r7, %[m] \n\
mov r8, r1 \n\
loop%=: \n\
ldrh r0, [r6, #2] \n\
ldrh r1, [r7, #2] \n\
mul r0, r3 \n\
mul r1, r4 \n\
add r2, r0, r2 \n\
ldrh r0, [r5, #2] \n\
add r2, r1, r2 \n\
mov r1, r8 \n\
add r2, r0, r2 \n\
and r1, r2 \n\
lsr r2, r2, #15 \n\
strh r1, [r5, #0] \n\
\n\
ldrh r0, [r6, #4] \n\
ldrh r1, [r7, #4] \n\
mul r0, r3 \n\
mul r1, r4 \n\
add r2, r0, r2 \n\
ldrh r0, [r5, #4] \n\
add r2, r1, r2 \n\
mov r1, r8 \n\
add r2, r0, r2 \n\
and r1, r2 \n\
lsr r2, r2, #15 \n\
strh r1, [r5, #2] \n\
\n\
ldrh r0, [r6, #6] \n\
ldrh r1, [r7, #6] \n\
mul r0, r3 \n\
mul r1, r4 \n\
add r2, r0, r2 \n\
ldrh r0, [r5, #6] \n\
add r2, r1, r2 \n\
mov r1, r8 \n\
add r2, r0, r2 \n\
and r1, r2 \n\
lsr r2, r2, #15 \n\
strh r1, [r5, #4] \n\
\n\
ldrh r0, [r6, #8] \n\
ldrh r1, [r7, #8] \n\
mul r0, r3 \n\
mul r1, r4 \n\
add r2, r0, r2 \n\
ldrh r0, [r5, #8] \n\
add r2, r1, r2 \n\
mov r1, r8 \n\
add r2, r0, r2 \n\
and r1, r2 \n\
lsr r2, r2, #15 \n\
strh r1, [r5, #6] \n\
\n\
add r5, r5, #8 \n\
add r6, r6, #8 \n\
add r7, r7, #8 \n\
cmp r5, r9 \n\
bne loop%= \n\
\n\
str r2, %[carry] \n\
"
: [carry] "=m" (r)
: [xu] "m" (xu), [f] "m" (f), [d] "m" (d), [y] "m" (y),
[m] "m" (m), [limit] "m" (limit)
: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r8", "r9" );
} else {
r = 0;
}
v = len4;
#else
r = 0;
for (v = 0; v < len4; v += 4) {
uint32_t z;
z = d[v + 1] + MUL15(xu, y[v + 1])
+ MUL15(f, m[v + 1]) + r;
r = z >> 15;
d[v + 0] = z & 0x7FFF;
z = d[v + 2] + MUL15(xu, y[v + 2])
+ MUL15(f, m[v + 2]) + r;
r = z >> 15;
d[v + 1] = z & 0x7FFF;
z = d[v + 3] + MUL15(xu, y[v + 3])
+ MUL15(f, m[v + 3]) + r;
r = z >> 15;
d[v + 2] = z & 0x7FFF;
z = d[v + 4] + MUL15(xu, y[v + 4])
+ MUL15(f, m[v + 4]) + r;
r = z >> 15;
d[v + 3] = z & 0x7FFF;
}
#endif
for (; v < len; v ++) {
uint32_t z;
z = d[v + 1] + MUL15(xu, y[v + 1])
+ MUL15(f, m[v + 1]) + r;
r = z >> 15;
d[v + 0] = z & 0x7FFF;
}
zh = dh + r;
d[len] = zh & 0x7FFF;
dh = zh >> 15;
}
/*
* Restore the bit length (it was overwritten in the loop above).
*/
d[0] = m[0];
/*
* d[] may be greater than m[], but it is still lower than twice
* the modulus.
*/
br_i15_sub(d, m, NEQ(dh, 0) | NOT(br_i15_sub(d, m, 0)));
}
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