a55df2793
Denys Vlasenko
2013-01-15
Subject
sha3: code shrink
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libbb/hash_md5_sha.c+18 -13
| @@ -988,24 +988,29 @@ static void KeccakF(uint64_t *state) | |
| for (round = 0; round < cKeccakNumberOfRounds; ++round) { | |
| /* Theta */ | |
| { | |
| - | uint64_t BC[5]; |
| + | uint64_t BC[10]; |
| for (x = 0; x < 5; ++x) { | |
| - | BC[x] = state[x] ^ state[5 + x] ^ state[10 + x] ^ |
| - | state[15 + x] ^ state[20 + x]; |
| + | BC[x + 5] = BC[x] = state[x] |
| + | ^ state[x + 5] ^ state[x + 10] |
| + | ^ state[x + 15] ^ state[x + 20]; |
| } | |
| + | /* Using 2x5 vector above eliminates the need to use |
| + | * [Mod5[x+N]] index trick below to calculate (x+N) % 5, |
| + | * and the code is a bit _smaller_. |
| + | */ |
| for (x = 0; x < 5; ++x) { | |
| - | uint64_t temp = BC[KeccakF_Mod5[x + 4]] ^ |
| - | rotl64(BC[KeccakF_Mod5[x + 1]], 1); |
| + | uint64_t temp = BC[x + 4] ^ rotl64(BC[x + 1], 1); |
| if (SHA3_SMALL && !ARCH_IS_64BIT) { | |
| for (y = 0; y <= 20; y += 5) | |
| - | state[y + x] ^= temp; |
| + | state[x + y] ^= temp; |
| } else { | |
| - | /* on 64-bit arch, this is actually smaller too */ |
| - | state[0 + x] ^= temp; |
| - | state[5 + x] ^= temp; |
| - | state[10 + x] ^= temp; |
| - | state[15 + x] ^= temp; |
| - | state[20 + x] ^= temp; |
| + | /* On 64-bit, this is also smaller, |
| + | * not only faster, than loop */ |
| + | state[x] ^= temp; |
| + | state[x + 5] ^= temp; |
| + | state[x + 10] ^= temp; |
| + | state[x + 15] ^= temp; |
| + | state[x + 20] ^= temp; |
| } | |
| } | |
| } | |
| @@ -1019,7 +1024,7 @@ static void KeccakF(uint64_t *state) | |
| t1 = t0; | |
| } | |
| } else { | |
| - | /* Especially large benefit for 32-bit arch: |
| + | /* Especially large benefit for 32-bit arch (75% faster): |
| * 64-bit rotations by non-constant usually are SLOW on those. | |
| * We resort to unrolling here. | |
| * This optimizes out KeccakF_PiLane[] and KeccakF_RotationConstants[], | |