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Improve code clarity for the set lookup logic #20028

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merged 2 commits into from
May 10, 2020
Merged

Improve code clarity for the set lookup logic #20028

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37f079e
Improve code clarity for the set lookup logic
rhettinger May 10, 2020
e650fef
Improve variable name
rhettinger May 10, 2020
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180 changes: 55 additions & 125 deletions Objects/setobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -57,77 +57,43 @@ set_lookkey(PySetObject *so, PyObject *key, Py_hash_t hash)
{
setentry *table;
setentry *entry;
size_t perturb;
size_t perturb = hash;
size_t mask = so->mask;
size_t i = (size_t)hash & mask; /* Unsigned for defined overflow behavior */
size_t j;
int probes;
int cmp;

entry = &so->table[i];
if (entry->key == NULL)
return entry;

perturb = hash;

while (1) {
if (entry->hash == hash) {
PyObject *startkey = entry->key;
/* startkey cannot be a dummy because the dummy hash field is -1 */
assert(startkey != dummy);
if (startkey == key)
return entry;
if (PyUnicode_CheckExact(startkey)
&& PyUnicode_CheckExact(key)
&& _PyUnicode_EQ(startkey, key))
return entry;
table = so->table;
Py_INCREF(startkey);
cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
Py_DECREF(startkey);
if (cmp < 0) /* unlikely */
return NULL;
if (table != so->table || entry->key != startkey) /* unlikely */
return set_lookkey(so, key, hash);
if (cmp > 0) /* likely */
entry = &so->table[i];
probes = (i + LINEAR_PROBES <= mask) ? LINEAR_PROBES: 0;
do {
if (entry->hash == 0 && entry->key == NULL)
return entry;
mask = so->mask; /* help avoid a register spill */
}

if (i + LINEAR_PROBES <= mask) {
for (j = 0 ; j < LINEAR_PROBES ; j++) {
entry++;
if (entry->hash == 0 && entry->key == NULL)
if (entry->hash == hash) {
PyObject *startkey = entry->key;
assert(startkey != dummy);
if (startkey == key)
return entry;
if (entry->hash == hash) {
PyObject *startkey = entry->key;
assert(startkey != dummy);
if (startkey == key)
return entry;
if (PyUnicode_CheckExact(startkey)
&& PyUnicode_CheckExact(key)
&& _PyUnicode_EQ(startkey, key))
return entry;
table = so->table;
Py_INCREF(startkey);
cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
Py_DECREF(startkey);
if (cmp < 0)
return NULL;
if (table != so->table || entry->key != startkey)
return set_lookkey(so, key, hash);
if (cmp > 0)
return entry;
mask = so->mask;
}
if (PyUnicode_CheckExact(startkey)
&& PyUnicode_CheckExact(key)
&& _PyUnicode_EQ(startkey, key))
return entry;
table = so->table;
Py_INCREF(startkey);
cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
Py_DECREF(startkey);
if (cmp < 0)
return NULL;
if (table != so->table || entry->key != startkey)
return set_lookkey(so, key, hash);
if (cmp > 0)
return entry;
mask = so->mask;
}
}

entry++;
} while (probes--);
perturb >>= PERTURB_SHIFT;
i = (i * 5 + 1 + perturb) & mask;

entry = &so->table[i];
if (entry->key == NULL)
return entry;
}
}

Expand All @@ -141,7 +107,7 @@ set_add_entry(PySetObject *so, PyObject *key, Py_hash_t hash)
size_t perturb;
size_t mask;
size_t i; /* Unsigned for defined overflow behavior */
size_t j;
int probes;
int cmp;

/* Pre-increment is necessary to prevent arbitrary code in the rich
Expand All @@ -152,75 +118,39 @@ set_add_entry(PySetObject *so, PyObject *key, Py_hash_t hash)

mask = so->mask;
i = (size_t)hash & mask;

entry = &so->table[i];
if (entry->key == NULL)
goto found_unused;

perturb = hash;

while (1) {
if (entry->hash == hash) {
PyObject *startkey = entry->key;
/* startkey cannot be a dummy because the dummy hash field is -1 */
assert(startkey != dummy);
if (startkey == key)
goto found_active;
if (PyUnicode_CheckExact(startkey)
&& PyUnicode_CheckExact(key)
&& _PyUnicode_EQ(startkey, key))
goto found_active;
table = so->table;
Py_INCREF(startkey);
cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
Py_DECREF(startkey);
if (cmp > 0) /* likely */
goto found_active;
if (cmp < 0)
goto comparison_error;
/* Continuing the search from the current entry only makes
sense if the table and entry are unchanged; otherwise,
we have to restart from the beginning */
if (table != so->table || entry->key != startkey)
goto restart;
mask = so->mask; /* help avoid a register spill */
}

if (i + LINEAR_PROBES <= mask) {
for (j = 0 ; j < LINEAR_PROBES ; j++) {
entry++;
if (entry->hash == 0 && entry->key == NULL)
goto found_unused;
if (entry->hash == hash) {
PyObject *startkey = entry->key;
assert(startkey != dummy);
if (startkey == key)
goto found_active;
if (PyUnicode_CheckExact(startkey)
&& PyUnicode_CheckExact(key)
&& _PyUnicode_EQ(startkey, key))
goto found_active;
table = so->table;
Py_INCREF(startkey);
cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
Py_DECREF(startkey);
if (cmp > 0)
goto found_active;
if (cmp < 0)
goto comparison_error;
if (table != so->table || entry->key != startkey)
goto restart;
mask = so->mask;
}
entry = &so->table[i];
probes = (i + LINEAR_PROBES <= mask) ? LINEAR_PROBES: 0;
do {
if (entry->hash == 0 && entry->key == NULL)
goto found_unused;
if (entry->hash == hash) {
PyObject *startkey = entry->key;
assert(startkey != dummy);
if (startkey == key)
goto found_active;
if (PyUnicode_CheckExact(startkey)
&& PyUnicode_CheckExact(key)
&& _PyUnicode_EQ(startkey, key))
goto found_active;
table = so->table;
Py_INCREF(startkey);
cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
Py_DECREF(startkey);
if (cmp > 0)
goto found_active;
if (cmp < 0)
goto comparison_error;
if (table != so->table || entry->key != startkey)
goto restart;
mask = so->mask;
}
}

entry++;
} while (probes--);
perturb >>= PERTURB_SHIFT;
i = (i * 5 + 1 + perturb) & mask;

entry = &so->table[i];
if (entry->key == NULL)
goto found_unused;
}

found_unused:
Expand Down