bbd723ebe
Denys Vlasenko
2021-10-05
Subject
tls: optimize sp_256_mul_8 in P256
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networking/tls_sp_c32.c+82 -2
| @@ -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. */ | |