87e3f2e9f
Denys Vlasenko
2021-10-06
Subject
tls: P256: x86-64 optimized sp_256_sub_8_p256_mod
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networking/tls_sp_c32.c+31 -1
| @@ -346,8 +346,8 @@ static int sp_256_sub_8(sp_digit* r, const sp_digit* a, const sp_digit* b) | |
| #endif | |
| } | |
| - | #if ALLOW_ASM && defined(__GNUC__) && defined(__i386__) |
| /* Sub p256_mod from a into r. (r = a - p256_mod). */ | |
| + | #if ALLOW_ASM && defined(__GNUC__) && defined(__i386__) |
| static void sp_256_sub_8_p256_mod(sp_digit* r, const sp_digit* a) | |
| { | |
| sp_digit reg; | |
| @@ -390,6 +390,36 @@ static void sp_256_sub_8_p256_mod(sp_digit* r, const sp_digit* a) | |
| : "memory" | |
| ); | |
| } | |
| + | #elif ALLOW_ASM && defined(__GNUC__) && defined(__x86_64__) |
| + | static void sp_256_sub_8_p256_mod(sp_digit* r, const sp_digit* a) |
| + | { |
| + | uint64_t reg; |
| + | uint64_t ooff; |
| + | //p256_mod[3..0] = ffffffff00000001 0000000000000000 00000000ffffffff ffffffffffffffff |
| + | asm volatile ( |
| + | "\n movq (%0), %3" |
| + | "\n addq $1, %3" // adding 1 is the same as subtracting ffffffffffffffff |
| + | "\n movq %3, (%1)" // |
| + | "\n cmc" // only carry bit needs inverting |
| + | "\n" |
| + | "\n movq 1*8(%0), %3" |
| + | "\n sbbq %2, %3" // %2 holds 00000000ffffffff |
| + | "\n movq %3, 1*8(%1)" |
| + | "\n" |
| + | "\n movq 2*8(%0), %3" |
| + | "\n sbbq $0, %3" |
| + | "\n movq %3, 2*8(%1)" |
| + | "\n" |
| + | "\n movq 3*8(%0), %3" |
| + | "\n sbbq $0, %3" // adding 00000000ffffffff (in %2) |
| + | "\n addq %2, %3" // is the same as subtracting ffffffff00000001 |
| + | "\n movq %3, 3*8(%1)" |
| + | "\n" |
| + | : "=r" (a), "=r" (r), "=r" (ooff), "=r" (reg) |
| + | : "0" (a), "1" (r), "2" (0x00000000ffffffff) |
| + | : "memory" |
| + | ); |
| + | } |
| #else | |
| # define sp_256_sub_8_p256_mod(r, a) sp_256_sub_8((r), (a), p256_mod) | |
| #endif | |