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GH-131798: Optimize cached class attributes and methods in the JIT (GH-134403)

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Brandt Bucher 2025-05-22 11:15:03 -04:00 • committed by GitHub
parent 09e72cf091
commit ec736e7dae
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12 changed files with 365 additions and 130 deletions
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78
Python/optimizer_symbols.c
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@ -13,22 +13,46 @@
#include <stdint.h>
#include <stddef.h>
/* Symbols
=======
/*
See the diagram at
https://github.com/faster-cpython/ideas/blob/main/3.13/redundancy_eliminator.md
Symbols
=======
We represent the nodes in the diagram as follows
(the flag bits are only defined in optimizer_symbols.c):
- Top: no flag bits, typ and const_val are NULL.
- NULL: IS_NULL flag set, type and const_val NULL.
- Not NULL: NOT_NULL flag set, type and const_val NULL.
- None/not None: not used. (None could be represented as any other constant.)
- Known type: NOT_NULL flag set and typ set; const_val is NULL.
- Known constant: NOT_NULL flag set, type set, const_val set.
- Bottom: IS_NULL and NOT_NULL flags set, type and const_val NULL.
*/
https://github.com/faster-cpython/ideas/blob/main/3.13/redundancy_eliminator.md
Logically, all symbols begin as UNKNOWN, and can transition downwards along the
edges of the lattice, but *never* upwards (see the diagram below). The UNKNOWN
state represents no information, and the BOTTOM state represents contradictory
information. Though symbols logically progress through all intermediate nodes,
we often skip in-between states for convenience:
UNKNOWN
| |
NULL |
| | <- Anything below this level is an object.
| NON_NULL
| | | <- Anything below this level has a known type version.
| TYPE_VERSION |
| | | <- Anything below this level has a known type.
| KNOWN_CLASS |
| | | | <- Anything below this level has a known truthiness.
| | | TRUTHINESS
| | | |
| TUPLE | |
| | | | <- Anything below this level is a known constant.
| KNOWN_VALUE
| | <- Anything below this level is unreachable.
BOTTOM
For example, after guarding that the type of an UNKNOWN local is int, we can
narrow the symbol to KNOWN_CLASS (logically progressing though NON_NULL and
TYPE_VERSION to get there). Later, we may learn that it is falsey based on the
result of a truth test, which would allow us to narrow the symbol to KNOWN_VALUE
(with a value of integer zero). If at any point we encounter a float guard on
the same symbol, that would be a contradiction, and the symbol would be set to
BOTTOM (indicating that the code is unreachable).
*/
#ifdef Py_DEBUG
static inline int get_lltrace(void) {
@ -420,7 +444,6 @@ _Py_uop_sym_get_type(JitOptSymbol *sym)
JitSymType tag = sym->tag;
switch(tag) {
case JIT_SYM_NULL_TAG:
case JIT_SYM_TYPE_VERSION_TAG:
case JIT_SYM_BOTTOM_TAG:
case JIT_SYM_NON_NULL_TAG:
case JIT_SYM_UNKNOWN_TAG:
@ -429,6 +452,8 @@ _Py_uop_sym_get_type(JitOptSymbol *sym)
return sym->cls.type;
case JIT_SYM_KNOWN_VALUE_TAG:
return Py_TYPE(sym->value.value);
case JIT_SYM_TYPE_VERSION_TAG:
return _PyType_LookupByVersion(sym->version.version);
case JIT_SYM_TUPLE_TAG:
return &PyTuple_Type;
case JIT_SYM_TRUTHINESS_TAG:
@ -464,21 +489,7 @@ _Py_uop_sym_get_type_version(JitOptSymbol *sym)
bool
_Py_uop_sym_has_type(JitOptSymbol *sym)
{
JitSymType tag = sym->tag;
switch(tag) {
case JIT_SYM_NULL_TAG:
case JIT_SYM_TYPE_VERSION_TAG:
case JIT_SYM_BOTTOM_TAG:
case JIT_SYM_NON_NULL_TAG:
case JIT_SYM_UNKNOWN_TAG:
return false;
case JIT_SYM_KNOWN_CLASS_TAG:
case JIT_SYM_KNOWN_VALUE_TAG:
case JIT_SYM_TUPLE_TAG:
case JIT_SYM_TRUTHINESS_TAG:
return true;
}
Py_UNREACHABLE();
return _Py_uop_sym_get_type(sym) != NULL;
}
bool
@ -576,7 +587,7 @@ _Py_uop_sym_tuple_getitem(JitOptContext *ctx, JitOptSymbol *sym, int item)
else if (sym->tag == JIT_SYM_TUPLE_TAG && item < sym->tuple.length) {
return allocation_base(ctx) + sym->tuple.items[item];
}
return _Py_uop_sym_new_unknown(ctx);
return _Py_uop_sym_new_not_null(ctx);
}
int
@ -863,6 +874,11 @@ _Py_uop_symbols_test(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(ignored))
_Py_uop_sym_get_const(ctx, _Py_uop_sym_tuple_getitem(ctx, sym, 1)) == val_43,
"tuple item does not match value used to create tuple"
);
sym = _Py_uop_sym_new_type(ctx, &PyTuple_Type);
TEST_PREDICATE(
_Py_uop_sym_is_not_null(_Py_uop_sym_tuple_getitem(ctx, sym, 42)),
"Unknown tuple item is not narrowed to non-NULL"
);
JitOptSymbol *value = _Py_uop_sym_new_type(ctx, &PyBool_Type);
sym = _Py_uop_sym_new_truthiness(ctx, value, false);
TEST_PREDICATE(_Py_uop_sym_matches_type(sym, &PyBool_Type), "truthiness is not boolean");