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Improve mbedtls_xor for IAR

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2024-01-19 14:02:08 +00:00
parent 4d4891e18a
commit 69b5a86064
1 changed files with 21 additions and 4 deletions
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25
library/common.h
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@ -191,21 +191,30 @@ inline void mbedtls_xor(unsigned char *r, const unsigned char *a, const unsigned
uint8x16_t x = veorq_u8(v1, v2);
vst1q_u8(r + i, x);
}
// This if statement helps some compilers (e.g., IAR) optimise out the byte-by-byte tail case
// where n is a constant multiple of 16.
// It makes no difference for others (e.g. recent gcc and clang) if n is a compile-time
// constant, and very little difference if n is not a compile-time constant.
if (n % 16 != 0)
#elif defined(MBEDTLS_ARCH_IS_X64) || defined(MBEDTLS_ARCH_IS_ARM64)
/* This codepath probably only makes sense on architectures with 64-bit registers */
for (; (i + 8) <= n; i += 8) {
uint64_t x = mbedtls_get_unaligned_uint64(a + i) ^ mbedtls_get_unaligned_uint64(b + i);
mbedtls_put_unaligned_uint64(r + i, x);
}
if (n % 8 != 0)
#else
for (; (i + 4) <= n; i += 4) {
uint32_t x = mbedtls_get_unaligned_uint32(a + i) ^ mbedtls_get_unaligned_uint32(b + i);
mbedtls_put_unaligned_uint32(r + i, x);
}
if (n % 4 != 0)
#endif
#endif
for (; i < n; i++) {
r[i] = a[i] ^ b[i];
{
for (; i < n; i++) {
r[i] = a[i] ^ b[i];
}
}
}
@ -236,15 +245,23 @@ static inline void mbedtls_xor_no_simd(unsigned char *r,
uint64_t x = mbedtls_get_unaligned_uint64(a + i) ^ mbedtls_get_unaligned_uint64(b + i);
mbedtls_put_unaligned_uint64(r + i, x);
}
// This if statement helps some compilers (e.g., IAR) optimise out the byte-by-byte tail case
// where n is a constant multiple of 8.
// It makes no difference for others (e.g. recent gcc and clang) if n is a compile-time
// constant, and very little difference if n is not a compile-time constant.
if (n % 8 != 0)
#else
for (; (i + 4) <= n; i += 4) {
uint32_t x = mbedtls_get_unaligned_uint32(a + i) ^ mbedtls_get_unaligned_uint32(b + i);
mbedtls_put_unaligned_uint32(r + i, x);
}
if (n % 4 != 0)
#endif
#endif
for (; i < n; i++) {
r[i] = a[i] ^ b[i];
{
for (; i < n; i++) {
r[i] = a[i] ^ b[i];
}
}
}