diff options
| -rw-r--r-- | erts/emulator/beam/utils.c | 43 |
1 files changed, 6 insertions, 37 deletions
diff --git a/erts/emulator/beam/utils.c b/erts/emulator/beam/utils.c index 9263798a28..cdf766b206 100644 --- a/erts/emulator/beam/utils.c +++ b/erts/emulator/beam/utils.c @@ -1581,9 +1581,6 @@ Uint32 make_internal_hash(Eterm term) { Uint32 hash; - Uint32 hash_xor_pairs; - - ERTS_UNDEF(hash_xor_pairs, 0); /* Optimization. Simple cases before declaration of estack. */ if (primary_tag(term) == TAG_PRIMARY_IMMED1) { @@ -1664,6 +1661,11 @@ make_internal_hash(Eterm term) Eterm* ptr = boxed_val(term) + 1; Uint size; int i; + + /* + * We rely on key-value iteration order being constant + * for identical maps (in this VM instance). + */ switch (hdr & _HEADER_MAP_SUBTAG_MASK) { case HAMT_SUBTAG_HEAD_FLATMAP: { @@ -1675,26 +1677,10 @@ make_internal_hash(Eterm term) if (size == 0) goto pop_next; - /* We want a hash function that is *independent* of - * the order in which keys and values are encountered. - * We therefore calculate context independent hashes for all . - * key-value pairs and then xor them together. - * - * We *do* need to use an initial seed for each pair, i.e. the - * hash value, so the hash value is reset for each pair with 'hash'. - * If we don't, no additional entropy is given to the system and the - * hash collision resolution in maps:from_list/1 would fail. - */ - ESTACK_PUSH(s, hash_xor_pairs); - ESTACK_PUSH(s, hash); - ESTACK_PUSH(s, HASH_MAP_TAIL); for (i = size - 1; i >= 0; i--) { - ESTACK_PUSH(s, hash); /* initial seed for all pairs */ - ESTACK_PUSH(s, HASH_MAP_PAIR); ESTACK_PUSH(s, vs[i]); ESTACK_PUSH(s, ks[i]); } - hash_xor_pairs = 0; goto pop_next; } case HAMT_SUBTAG_HEAD_ARRAY: @@ -1703,10 +1689,6 @@ make_internal_hash(Eterm term) UINT32_HASH(size, HCONST_16); if (size == 0) goto pop_next; - ESTACK_PUSH(s, hash_xor_pairs); - ESTACK_PUSH(s, hash); - ESTACK_PUSH(s, HASH_MAP_TAIL); - hash_xor_pairs = 0; } switch (hdr & _HEADER_MAP_SUBTAG_MASK) { case HAMT_SUBTAG_HEAD_ARRAY: @@ -1722,8 +1704,6 @@ make_internal_hash(Eterm term) while (i) { if (is_list(*ptr)) { Eterm* cons = list_val(*ptr); - ESTACK_PUSH(s, hash); /* initial seed for all pairs */ - ESTACK_PUSH(s, HASH_MAP_PAIR); ESTACK_PUSH(s, CDR(cons)); ESTACK_PUSH(s, CAR(cons)); } @@ -1739,7 +1719,7 @@ make_internal_hash(Eterm term) case EXPORT_SUBTAG: { Export* ep = *((Export **) (export_val(term) + 1)); - /* Assumes Export entries never moves */ + /* Assumes Export entries never move */ POINTER_HASH(ep, HCONST_14); goto pop_next; } @@ -1919,17 +1899,6 @@ make_internal_hash(Eterm term) term = ESTACK_POP(s); switch (term) { - case HASH_MAP_TAIL: { - hash = (Uint32) ESTACK_POP(s); - UINT32_HASH(hash_xor_pairs, HCONST_19); - hash_xor_pairs = (Uint32) ESTACK_POP(s); - goto pop_next; - } - case HASH_MAP_PAIR: - hash_xor_pairs ^= hash; - hash = (Uint32) ESTACK_POP(s); /* initial seed for all pairs */ - goto pop_next; - case HASH_CDR: CONST_HASH(HCONST_18); /* Hash CDR i cons cell */ goto pop_next; |