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Change hash_hash_t to uint32_t

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This saves a lot of memory and is quite sufficient.  Hash functions
are adapted to produce a hash_hash_t eventually, which eliminates some
useless and information-destroying intermediate hash reduction steps.

We still use EMACS_UINT for most of the actual hashing steps before
producing the final value; this may be slightly wasteful on 32-bit
platforms with 64-bit EMACS_UINT.

* src/lisp.h (hash_hash_t): Change to uint32_t.
* src/fns.c (reduce_emacs_uint_to_hash_hash): New.
(hashfn_eq, hashfn_equal, hashfn_user_defined): Reduce return values
to hash_hash_t.
(sxhash_string): Remove.  Caller changed to hash_string.
(sxhash_float, sxhash_list, sxhash_vector, sxhash_bool_vector)
(sxhash_bignum): Remove wasteful calls to SXHASH_REDUCE.
(hash_hash_to_fixnum): New.
(Fsxhash_eq, Fsxhash_eql, Fsxhash_equal)
(Fsxhash_equal_including_properties): Convert return values to fixnum.
This commit is contained in:
Mattias Engdegård 2023-11-22 14:54:34 +01:00
parent 11e467eb60
commit 1998039f7a
2 changed files with 43 additions and 36 deletions
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77
src/fns.c
View file

@ -4452,6 +4452,16 @@ cmpfn_user_defined (Lisp_Object key1, Lisp_Object key2,
return hash_table_user_defined_call (ARRAYELTS (args), args, h);
}
/* Reduce an EMACS_UINT hash value to hash_hash_t. */
static inline hash_hash_t
reduce_emacs_uint_to_hash_hash (EMACS_UINT x)
{
verify (sizeof x <= 2 * sizeof (hash_hash_t));
return (sizeof x == sizeof (hash_hash_t)
? x
: x ^ (x >> (8 * (sizeof x - sizeof (hash_hash_t)))));
}
/* Ignore H and return a hash code for KEY which uses 'eq' to compare keys. */
static hash_hash_t
@ -4459,21 +4469,18 @@ hashfn_eq (Lisp_Object key, struct Lisp_Hash_Table *h)
{
if (symbols_with_pos_enabled && SYMBOL_WITH_POS_P (key))
key = SYMBOL_WITH_POS_SYM (key);
return XHASH (key) ^ XTYPE (key);
return reduce_emacs_uint_to_hash_hash (XHASH (key) ^ XTYPE (key));
}
/* Ignore H and return a hash code for KEY which uses 'equal' to compare keys.
The hash code is at most INTMASK. */
/* Ignore H and return a hash code for KEY which uses 'equal' to
compare keys. */
static hash_hash_t
hashfn_equal (Lisp_Object key, struct Lisp_Hash_Table *h)
{
return sxhash (key);
return reduce_emacs_uint_to_hash_hash (sxhash (key));
}
/* Ignore H and return a hash code for KEY which uses 'eql' to compare keys.
The hash code is at most INTMASK. */
/* Ignore H and return a hash code for KEY which uses 'eql' to compare keys. */
static hash_hash_t
hashfn_eql (Lisp_Object key, struct Lisp_Hash_Table *h)
{
@ -4489,7 +4496,8 @@ hashfn_user_defined (Lisp_Object key, struct Lisp_Hash_Table *h)
{
Lisp_Object args[] = { h->test->user_hash_function, key };
Lisp_Object hash = hash_table_user_defined_call (ARRAYELTS (args), args, h);
return FIXNUMP (hash) ? XUFIXNUM(hash) : sxhash (hash);
return reduce_emacs_uint_to_hash_hash (FIXNUMP (hash)
? XUFIXNUM(hash) : sxhash (hash));
}
struct hash_table_test const
@ -5061,16 +5069,6 @@ hash_string (char const *ptr, ptrdiff_t len)
return hash;
}
/* Return a hash for string PTR which has length LEN. The hash
code returned is at most INTMASK. */
static EMACS_UINT
sxhash_string (char const *ptr, ptrdiff_t len)
{
EMACS_UINT hash = hash_string (ptr, len);
return SXHASH_REDUCE (hash);
}
/* Return a hash for the floating point value VAL. */
static EMACS_UINT
@ -5080,7 +5078,7 @@ sxhash_float (double val)
union double_and_words u = { .val = val };
for (int i = 0; i < WORDS_PER_DOUBLE; i++)
hash = sxhash_combine (hash, u.word[i]);
return SXHASH_REDUCE (hash);
return hash;
}
/* Return a hash for list LIST. DEPTH is the current depth in the
@ -5107,7 +5105,7 @@ sxhash_list (Lisp_Object list, int depth)
hash = sxhash_combine (hash, hash2);
}
return SXHASH_REDUCE (hash);
return hash;
}
@ -5127,7 +5125,7 @@ sxhash_vector (Lisp_Object vec, int depth)
hash = sxhash_combine (hash, hash2);
}
return SXHASH_REDUCE (hash);
return hash;
}
/* Return a hash for bool-vector VECTOR. */
@ -5143,7 +5141,7 @@ sxhash_bool_vector (Lisp_Object vec)
for (i = 0; i < n; ++i)
hash = sxhash_combine (hash, bool_vector_data (vec)[i]);
return SXHASH_REDUCE (hash);
return hash;
}
/* Return a hash for a bignum. */
@ -5158,19 +5156,18 @@ sxhash_bignum (Lisp_Object bignum)
for (i = 0; i < nlimbs; ++i)
hash = sxhash_combine (hash, mpz_getlimbn (*n, i));
return SXHASH_REDUCE (hash);
return hash;
}
/* Return a hash code for OBJ. DEPTH is the current depth in the Lisp
structure. Value is an unsigned integer clipped to INTMASK. */
EMACS_UINT
sxhash (Lisp_Object obj)
{
return sxhash_obj (obj, 0);
}
/* Return a hash code for OBJ. DEPTH is the current depth in the Lisp
structure. */
static EMACS_UINT
sxhash_obj (Lisp_Object obj, int depth)
{
@ -5186,7 +5183,7 @@ sxhash_obj (Lisp_Object obj, int depth)
return XHASH (obj);
case Lisp_String:
return sxhash_string (SSDATA (obj), SBYTES (obj));
return hash_string (SSDATA (obj), SBYTES (obj));
case Lisp_Vectorlike:
{
@ -5213,7 +5210,7 @@ sxhash_obj (Lisp_Object obj, int depth)
= XMARKER (obj)->buffer ? XMARKER (obj)->bytepos : 0;
EMACS_UINT hash
= sxhash_combine ((intptr_t) XMARKER (obj)->buffer, bytepos);
return SXHASH_REDUCE (hash);
return hash;
}
else if (pvec_type == PVEC_BOOL_VECTOR)
return sxhash_bool_vector (obj);
@ -5222,7 +5219,7 @@ sxhash_obj (Lisp_Object obj, int depth)
EMACS_UINT hash = OVERLAY_START (obj);
hash = sxhash_combine (hash, OVERLAY_END (obj));
hash = sxhash_combine (hash, sxhash_obj (XOVERLAY (obj)->plist, depth));
return SXHASH_REDUCE (hash);
return hash;
}
else if (symbols_with_pos_enabled && pvec_type == PVEC_SYMBOL_WITH_POS)
return sxhash_obj (XSYMBOL_WITH_POS (obj)->sym, depth + 1);
@ -5258,6 +5255,15 @@ collect_interval (INTERVAL interval, Lisp_Object collector)
Lisp Interface
***********************************************************************/
/* Reduce X to a Lisp fixnum. */
static inline Lisp_Object
hash_hash_to_fixnum (hash_hash_t x)
{
return make_ufixnum (FIXNUM_BITS < 8 * sizeof x
? (x ^ x >> (8 * sizeof x - FIXNUM_BITS)) & INTMASK
: x);
}
DEFUN ("sxhash-eq", Fsxhash_eq, Ssxhash_eq, 1, 1, 0,
doc: /* Return an integer hash code for OBJ suitable for `eq'.
If (eq A B), then (= (sxhash-eq A) (sxhash-eq B)).
@ -5265,7 +5271,7 @@ If (eq A B), then (= (sxhash-eq A) (sxhash-eq B)).
Hash codes are not guaranteed to be preserved across Emacs sessions. */)
(Lisp_Object obj)
{
return make_ufixnum (hashfn_eq (obj, NULL));
return hash_hash_to_fixnum (hashfn_eq (obj, NULL));
}
DEFUN ("sxhash-eql", Fsxhash_eql, Ssxhash_eql, 1, 1, 0,
@ -5276,7 +5282,7 @@ isn't necessarily true.
Hash codes are not guaranteed to be preserved across Emacs sessions. */)
(Lisp_Object obj)
{
return make_ufixnum (hashfn_eql (obj, NULL));
return hash_hash_to_fixnum (hashfn_eql (obj, NULL));
}
DEFUN ("sxhash-equal", Fsxhash_equal, Ssxhash_equal, 1, 1, 0,
@ -5287,7 +5293,7 @@ opposite isn't necessarily true.
Hash codes are not guaranteed to be preserved across Emacs sessions. */)
(Lisp_Object obj)
{
return make_ufixnum (hashfn_equal (obj, NULL));
return hash_hash_to_fixnum (hashfn_equal (obj, NULL));
}
DEFUN ("sxhash-equal-including-properties", Fsxhash_equal_including_properties,
@ -5302,6 +5308,7 @@ Hash codes are not guaranteed to be preserved across Emacs sessions. */)
{
if (STRINGP (obj))
{
/* FIXME: This is very wasteful. We needn't cons at all. */
Lisp_Object collector = Fcons (Qnil, Qnil);
traverse_intervals (string_intervals (obj), 0, collect_interval,
collector);
@ -5311,7 +5318,7 @@ Hash codes are not guaranteed to be preserved across Emacs sessions. */)
sxhash (CDR (collector)))));
}
return make_ufixnum (hashfn_equal (obj, NULL));
return hash_hash_to_fixnum (hashfn_equal (obj, NULL));
}

2
src/lisp.h
View file

@ -2387,7 +2387,7 @@ struct Lisp_Hash_Table;
/* The type of a hash value stored in the table.
It's unsigned and a subtype of EMACS_UINT. */
typedef EMACS_UINT hash_hash_t;
typedef uint32_t hash_hash_t;
typedef enum {
Test_eql,