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tls: optimize sp_256_mul_8 in P256

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function                                             old     new   delta
sp_256_mont_mul_8                                    151     150      -1

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2021-10-05 23:19:18 +02:00
parent 3b411ebbfc
commit bbd723ebec
1 changed files with 82 additions and 2 deletions
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84
networking/tls_sp_c32.c
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@ -294,6 +294,85 @@ static int sp_256_sub_8(sp_digit* r, const sp_digit* a, const sp_digit* b)
/* Multiply a and b into r. (r = a * b) */
static void sp_256_mul_8(sp_digit* r, const sp_digit* a, const sp_digit* b)
{
#if ALLOW_ASM && defined(__GNUC__) && defined(__i386__)
sp_digit rr[15]; /* in case r coincides with a or b */
int k;
uint32_t accl;
uint32_t acch;
acch = accl = 0;
for (k = 0; k < 15; k++) {
int i, j;
uint32_t acc_hi;
i = k - 7;
if (i < 0)
i = 0;
j = k - i;
acc_hi = 0;
do {
////////////////////////
// uint64_t m = ((uint64_t)a[i]) * b[j];
// acc_hi:acch:accl += m;
asm volatile (
// a[i] is already loaded in %%eax
"\n mull %7"
"\n addl %%eax, %0"
"\n adcl %%edx, %1"
"\n adcl $0, %2"
: "=rm" (accl), "=rm" (acch), "=rm" (acc_hi)
: "0" (accl), "1" (acch), "2" (acc_hi), "a" (a[i]), "m" (b[j])
: "cc", "dx"
);
////////////////////////
j--;
i++;
} while (i != 8 && i <= k);
rr[k] = accl;
accl = acch;
acch = acc_hi;
}
r[15] = accl;
memcpy(r, rr, sizeof(rr));
#elif 0
//TODO: arm assembly (untested)
sp_digit tmp[16];
asm volatile (
"\n mov r5, #0"
"\n mov r6, #0"
"\n mov r7, #0"
"\n mov r8, #0"
"\n 1:"
"\n subs r3, r5, #28"
"\n movcc r3, #0"
"\n sub r4, r5, r3"
"\n 2:"
"\n ldr r14, [%[a], r3]"
"\n ldr r12, [%[b], r4]"
"\n umull r9, r10, r14, r12"
"\n adds r6, r6, r9"
"\n adcs r7, r7, r10"
"\n adc r8, r8, #0"
"\n add r3, r3, #4"
"\n sub r4, r4, #4"
"\n cmp r3, #32"
"\n beq 3f"
"\n cmp r3, r5"
"\n ble 2b"
"\n 3:"
"\n str r6, [%[r], r5]"
"\n mov r6, r7"
"\n mov r7, r8"
"\n mov r8, #0"
"\n add r5, r5, #4"
"\n cmp r5, #56"
"\n ble 1b"
"\n str r6, [%[r], r5]"
: [r] "r" (tmp), [a] "r" (a), [b] "r" (b)
: "memory", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10", "r14", "r12"
);
memcpy(r, tmp, sizeof(tmp));
#else
sp_digit rr[15]; /* in case r coincides with a or b */
int i, j, k;
uint64_t acc;
@ -306,19 +385,20 @@ static void sp_256_mul_8(sp_digit* r, const sp_digit* a, const sp_digit* b)
i = 0;
j = k - i;
acc_hi = 0;
while (i != 8 && i <= k) {
do {
uint64_t m = ((uint64_t)a[i]) * b[j];
acc += m;
if (acc < m)
acc_hi++;
j--;
i++;
}
} while (i != 8 && i <= k);
rr[k] = acc;
acc = (acc >> 32) | ((uint64_t)acc_hi << 32);
}
r[15] = acc;
memcpy(r, rr, sizeof(rr));
#endif
}
/* Shift number right one bit. Bottom bit is lost. */