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gh-115999: Refactor LOAD_GLOBAL specializations to avoid reloading {globals, builtins} keys (gh-124953)

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Each of the `LOAD_GLOBAL` specializations is implemented roughly as:

1. Load keys version.
2. Load cached keys version.
3. Deopt if (1) and (2) don't match.
4. Load keys.
5. Load cached index into keys.
6. Load object from (4) at offset from (5).

This is not thread-safe in free-threaded builds; the keys object may be replaced
in between steps (3) and (4).

This change refactors the specializations to avoid reloading the keys object and
instead pass the keys object from guards to be consumed by downstream uops.
This commit is contained in:
mpage 2024-10-09 08:18:25 -07:00 • committed by GitHub
parent b9a8ca0a6a
commit f978fb4f8d
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9 changed files with 379 additions and 162 deletions
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22
Python/generated_cases.c.h generated
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@ -6146,6 +6146,7 @@
next_instr += 5;
INSTRUCTION_STATS(LOAD_GLOBAL_BUILTIN);
static_assert(INLINE_CACHE_ENTRIES_LOAD_GLOBAL == 4, "incorrect cache size");
PyDictKeysObject *builtins_keys;
_PyStackRef res;
_PyStackRef null = PyStackRef_NULL;
/* Skip 1 cache entry */
@ -6157,19 +6158,19 @@
DEOPT_IF(dict->ma_keys->dk_version != version, LOAD_GLOBAL);
assert(DK_IS_UNICODE(dict->ma_keys));
}
// _GUARD_BUILTINS_VERSION
// _GUARD_BUILTINS_VERSION_PUSH_KEYS
{
uint16_t version = read_u16(&this_instr[3].cache);
PyDictObject *dict = (PyDictObject *)BUILTINS();
DEOPT_IF(!PyDict_CheckExact(dict), LOAD_GLOBAL);
DEOPT_IF(dict->ma_keys->dk_version != version, LOAD_GLOBAL);
assert(DK_IS_UNICODE(dict->ma_keys));
builtins_keys = dict->ma_keys;
assert(DK_IS_UNICODE(builtins_keys));
}
// _LOAD_GLOBAL_BUILTINS
// _LOAD_GLOBAL_BUILTINS_FROM_KEYS
{
uint16_t index = read_u16(&this_instr[4].cache);
PyDictObject *bdict = (PyDictObject *)BUILTINS();
PyDictUnicodeEntry *entries = DK_UNICODE_ENTRIES(bdict->ma_keys);
PyDictUnicodeEntry *entries = DK_UNICODE_ENTRIES(builtins_keys);
PyObject *res_o = entries[index].me_value;
DEOPT_IF(res_o == NULL, LOAD_GLOBAL);
Py_INCREF(res_o);
@ -6189,23 +6190,24 @@
next_instr += 5;
INSTRUCTION_STATS(LOAD_GLOBAL_MODULE);
static_assert(INLINE_CACHE_ENTRIES_LOAD_GLOBAL == 4, "incorrect cache size");
PyDictKeysObject *globals_keys;
_PyStackRef res;
_PyStackRef null = PyStackRef_NULL;
/* Skip 1 cache entry */
// _GUARD_GLOBALS_VERSION
// _GUARD_GLOBALS_VERSION_PUSH_KEYS
{
uint16_t version = read_u16(&this_instr[2].cache);
PyDictObject *dict = (PyDictObject *)GLOBALS();
DEOPT_IF(!PyDict_CheckExact(dict), LOAD_GLOBAL);
DEOPT_IF(dict->ma_keys->dk_version != version, LOAD_GLOBAL);
assert(DK_IS_UNICODE(dict->ma_keys));
globals_keys = dict->ma_keys;
assert(DK_IS_UNICODE(globals_keys));
}
/* Skip 1 cache entry */
// _LOAD_GLOBAL_MODULE
// _LOAD_GLOBAL_MODULE_FROM_KEYS
{
uint16_t index = read_u16(&this_instr[4].cache);
PyDictObject *dict = (PyDictObject *)GLOBALS();
PyDictUnicodeEntry *entries = DK_UNICODE_ENTRIES(dict->ma_keys);
PyDictUnicodeEntry *entries = DK_UNICODE_ENTRIES(globals_keys);
PyObject *res_o = entries[index].me_value;
DEOPT_IF(res_o == NULL, LOAD_GLOBAL);
Py_INCREF(res_o);