Improve code clarity for the set lookup logic (GH-20028)

Author: rhettinger

Objects/setobject.c

@@ -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;
  }
 }
 
@@ -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
@@ -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: