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tls: P256: x86-64 optimized sp_256_sub_8_p256_mod

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function                                             old     new   delta
sp_256_sub_8_p256_mod                                  -      53     +53
sp_256_mont_reduce_8                                 223     217      -6
sp_256_mont_dbl_8                                     38      32      -6
sp_256_ecc_mulmod_8                                 1535    1529      -6
sp_256_proj_point_dbl_8                              469     454     -15
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/4 up/down: 53/-33)             Total: 20 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2021-10-06 19:59:39 +02:00
parent 911344a998
commit 87e3f2e9f8
1 changed files with 31 additions and 1 deletions
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32
networking/tls_sp_c32.c
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@ -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