diff options
Diffstat (limited to '')
| -rw-r--r-- | libblake_internal_blake2s_output_digest.c | 39 |
1 files changed, 37 insertions, 2 deletions
diff --git a/libblake_internal_blake2s_output_digest.c b/libblake_internal_blake2s_output_digest.c index d7b891c..6b4a5da 100644 --- a/libblake_internal_blake2s_output_digest.c +++ b/libblake_internal_blake2s_output_digest.c @@ -4,8 +4,18 @@ static void encode_uint32_le(unsigned char *out, uint_least32_t value, size_t bytes) { + /* Adding LIKELY to indicate that the default case is the + * expected does not affact the output */ switch (bytes) { default: + /* + * The following optimisation have been tested: + * + * 1) Changing the default case, on amd64, to + * *(uint32_t *)out = (uint32_t)value; + * break; + * result: halved performance + */ out[3] = (unsigned char)((value >> 24) & 255); /* fall through */ case 3: @@ -27,6 +37,31 @@ libblake_internal_blake2s_output_digest(struct libblake_blake2s_state *state, si { size_t i, j; - for (i = 0, j = 0; i < output_len; i += 4, j += 1) - encode_uint32_le(&output[i], state->h[j], output_len - i); +#ifdef LITTLE_ENDIAN + if ((uint_least32_t)(UINT_LEAST32_C(0xFFFFffff) + 1) == 0) { + /* No noticeable performance benefit on amd64, however + * it signficantly reduces the translation size and + * a 37.5x performance benefit was seen on the 64-bit + * version on amd64; + * even though the compiler is smart enough to optimise + * `encode_uint32_le(&output[i], state->h[j], 4);` to a + * movq (on amd64), it is note smart enough to optimise + * the rest */ + memcpy(output, state->h, output_len); + return; + } +#endif + + /* Estimated to have similar performance benefit as above + * on big-endian machines */ + for (i = 0, j = 0; i + 4 < output_len; i += 4, j += 1) + encode_uint32_le(&output[i], state->h[j], 4); + encode_uint32_le(&output[i], state->h[j], output_len - i); + + /* + * Unoptimised code: + * + * for (i = 0, j = 0; i < output_len; i += 4, j += 1) + * encode_uint32_le(&output[i], state->h[j], output_len - i); + */ } |