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Add assembly versions of equal() and negative()

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This commit is contained in:
Frank Denis 2024-10-23 19:24:13 +02:00
parent d6dd9c3ce0
commit d0eb23e532
1 changed files with 21 additions and 1 deletions
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22
src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
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@ -609,18 +609,38 @@ ge25519_precomp_0(ge25519_precomp *h)
static unsigned char
equal(signed char b, signed char c)
{
#if defined(HAVE_INLINE_ASM) && defined(__x86_64__)
int32_t b32 = (int32_t) b, c32 = (int32_t) c, q32, z32;
__asm__ ("xorl %0,%0\n movl $1,%1\n cmpb %b3,%b2\n cmovel %1,%0" :
"=&r"(z32), "=&r"(q32) : "q"(b32), "q"(c32) : "cc");
return (unsigned char) z32;
#elif defined(HAVE_INLINE_ASM) && defined(__aarch64__)
unsigned char z;
__asm__ ("and %w0,%w1,255\n cmp %w0,%w2,uxtb\n cset %w0,eq" :
"=&r"(z) : "r"(b), "r"(c) : "cc");
return z;
#else
const unsigned char x = (unsigned char) b ^ (unsigned char) c; /* 0: yes; 1..255: no */
const uint32_t y = (uint32_t) x; /* 0: yes; 1..255: no */
return (((y - 1) >> 29) ^ optblocker_u8) >> 2; /* 1: yes; 0: no */
#endif
}
static unsigned char
negative(signed char b)
{
#if defined(HAVE_INLINE_ASM) && defined(__x86_64__)
__asm__ ("shrb $7,%0" : "+r"(b) : : "cc");
return b;
#elif defined(HAVE_INLINE_ASM) && defined(__aarch64__)
uint8_t x;
__asm__ ("ubfx %w0,%w1,7,1" : "=r"(x) : "r"(b) : );
return x;
#else
const uint8_t x = (uint8_t) b; /* 0..127: no 128..255: yes */
return ((x >> 5) ^ optblocker_u8) >> 2; /* 1: yes; 0: no */
#endif
}
static void