diff options
Diffstat (limited to 'libbb/hash_md5_sha.c')
| -rw-r--r-- | libbb/hash_md5_sha.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/libbb/hash_md5_sha.c b/libbb/hash_md5_sha.c index 053ebe2..faf485d 100644 --- a/libbb/hash_md5_sha.c +++ b/libbb/hash_md5_sha.c @@ -509,6 +509,27 @@ static void FAST_FUNC sha1_process_block64(sha1_ctx_t *ctx) d = ctx->hash[3]; e = ctx->hash[4]; +/* From kernel source comments: + * """ + * If you have 32 registers or more, the compiler can (and should) + * try to change the array[] accesses into registers. However, on + * machines with less than ~25 registers, that won't really work, + * and at least gcc will make an unholy mess of it. + * + * So to avoid that mess which just slows things down, we force + * the stores to memory to actually happen (we might be better off + * with a 'W(t)=(val);asm("":"+m" (W(t))' there instead, as + * suggested by Artur Skawina - that will also make gcc unable to + * try to do the silly "optimize away loads" part because it won't + * see what the value will be). + * """ + */ +#if defined(__i386__) +# define DO_NOT_TRY_PROPAGATING(m) asm("":"+m"(m)) +#else +# define DO_NOT_TRY_PROPAGATING(m) ((void)0) +#endif + #undef OP #define OP(A,B,C,D,E, n) \ do { \ @@ -517,6 +538,7 @@ static void FAST_FUNC sha1_process_block64(sha1_ctx_t *ctx) work += W[n & 15] = SWAP_BE32(((uint32_t*)ctx->wbuffer)[n]); \ if (n >= 16) \ work += W[n & 15] = rotl32(W[(n+13) & 15] ^ W[(n+8) & 15] ^ W[(n+2) & 15] ^ W[n & 15], 1); \ + DO_NOT_TRY_PROPAGATING(W[n & 15]); \ E += work + rotl32(A, 5) + rconsts[n / 20]; \ B = rotl32(B, 30); \ } while (0) |