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cpython/Python/optimizer_symbols.c

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#include "Python.h"
#include "cpython/optimizer.h"
#include "pycore_code.h"
#include "pycore_frame.h"
#include "pycore_long.h"
#include "pycore_optimizer.h"
#include <stdbool.h>
#include <stdint.h>
#include <stddef.h>
/* Symbols
=======
See the diagram at
https://github.com/faster-cpython/ideas/blob/main/3.13/redundancy_eliminator.md
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.
*/
// Flags for below.
#define IS_NULL 1 << 0
#define NOT_NULL 1 << 1
#ifdef Py_DEBUG
static inline int get_lltrace(void) {
char *uop_debug = Py_GETENV("PYTHON_OPT_DEBUG");
int lltrace = 0;
if (uop_debug != NULL && *uop_debug >= '0') {
lltrace = *uop_debug - '0'; // TODO: Parse an int and all that
}
return lltrace;
}
#define DPRINTF(level, ...) \
if (get_lltrace() >= (level)) { printf(__VA_ARGS__); }
#else
#define DPRINTF(level, ...)
#endif
static _Py_UopsSymbol *
sym_new(_Py_UOpsContext *ctx)
{
_Py_UopsSymbol *self = &ctx->t_arena.arena[ctx->t_arena.ty_curr_number];
if (ctx->t_arena.ty_curr_number >= ctx->t_arena.ty_max_number) {
OPT_STAT_INC(optimizer_failure_reason_no_memory);
DPRINTF(1, "out of space for symbolic expression type\n");
return NULL;
}
ctx->t_arena.ty_curr_number++;
self->flags = 0;
self->typ = NULL;
self->const_val = NULL;
return self;
}
static inline void
sym_set_flag(_Py_UopsSymbol *sym, int flag)
{
sym->flags |= flag;
}
static inline void
sym_set_bottom(_Py_UopsSymbol *sym)
{
sym_set_flag(sym, IS_NULL | NOT_NULL);
sym->typ = NULL;
Py_CLEAR(sym->const_val);
}
bool
_Py_uop_sym_is_bottom(_Py_UopsSymbol *sym)
{
if ((sym->flags & IS_NULL) && (sym->flags & NOT_NULL)) {
assert(sym->flags == (IS_NULL | NOT_NULL));
assert(sym->typ == NULL);
assert(sym->const_val == NULL);
return true;
}
return false;
}
bool
_Py_uop_sym_is_not_null(_Py_UopsSymbol *sym)
{
return sym->flags == NOT_NULL;
}
bool
_Py_uop_sym_is_null(_Py_UopsSymbol *sym)
{
return sym->flags == IS_NULL;
}
bool
_Py_uop_sym_is_const(_Py_UopsSymbol *sym)
{
return sym->const_val != NULL;
}
PyObject *
_Py_uop_sym_get_const(_Py_UopsSymbol *sym)
{
return sym->const_val;
}
bool
_Py_uop_sym_set_type(_Py_UopsSymbol *sym, PyTypeObject *typ)
{
assert(typ != NULL && PyType_Check(typ));
if (sym->flags & IS_NULL) {
sym_set_bottom(sym);
return false;
}
if (sym->typ != NULL) {
if (sym->typ != typ) {
sym_set_bottom(sym);
return false;
}
}
else {
sym_set_flag(sym, NOT_NULL);
sym->typ = typ;
}
return true;
}
bool
_Py_uop_sym_set_const(_Py_UopsSymbol *sym, PyObject *const_val)
{
assert(const_val != NULL);
if (sym->flags & IS_NULL) {
sym_set_bottom(sym);
return false;
}
PyTypeObject *typ = Py_TYPE(const_val);
if (sym->typ != NULL && sym->typ != typ) {
sym_set_bottom(sym);
return false;
}
if (sym->const_val != NULL) {
if (sym->const_val != const_val) {
// TODO: What if they're equal?
sym_set_bottom(sym);
return false;
}
}
else {
sym_set_flag(sym, NOT_NULL);
sym->typ = typ;
sym->const_val = Py_NewRef(const_val);
}
return true;
}
bool
_Py_uop_sym_set_null(_Py_UopsSymbol *sym)
{
sym_set_flag(sym, IS_NULL);
return !_Py_uop_sym_is_bottom(sym);
}
bool
_Py_uop_sym_set_non_null(_Py_UopsSymbol *sym)
{
sym_set_flag(sym, NOT_NULL);
return !_Py_uop_sym_is_bottom(sym);
}
_Py_UopsSymbol *
_Py_uop_sym_new_unknown(_Py_UOpsContext *ctx)
{
return sym_new(ctx);
}
_Py_UopsSymbol *
_Py_uop_sym_new_not_null(_Py_UOpsContext *ctx)
{
_Py_UopsSymbol *res = _Py_uop_sym_new_unknown(ctx);
if (res == NULL) {
return NULL;
}
sym_set_flag(res, NOT_NULL);
return res;
}
_Py_UopsSymbol *
_Py_uop_sym_new_type(_Py_UOpsContext *ctx, PyTypeObject *typ)
{
_Py_UopsSymbol *res = sym_new(ctx);
if (res == NULL) {
return NULL;
}
_Py_uop_sym_set_type(res, typ);
return res;
}
// Adds a new reference to const_val, owned by the symbol.
_Py_UopsSymbol *
_Py_uop_sym_new_const(_Py_UOpsContext *ctx, PyObject *const_val)
{
assert(const_val != NULL);
_Py_UopsSymbol *res = sym_new(ctx);
if (res == NULL) {
return NULL;
}
_Py_uop_sym_set_const(res, const_val);
return res;
}
_Py_UopsSymbol *
_Py_uop_sym_new_null(_Py_UOpsContext *ctx)
{
_Py_UopsSymbol *null_sym = _Py_uop_sym_new_unknown(ctx);
if (null_sym == NULL) {
return NULL;
}
_Py_uop_sym_set_null(null_sym);
return null_sym;
}
bool
_Py_uop_sym_has_type(_Py_UopsSymbol *sym)
{
if (_Py_uop_sym_is_bottom(sym)) {
return false;
}
return sym->typ != NULL;
}
bool
_Py_uop_sym_matches_type(_Py_UopsSymbol *sym, PyTypeObject *typ)
{
assert(typ != NULL && PyType_Check(typ));
if (_Py_uop_sym_is_bottom(sym)) {
return false;
}
return sym->typ == typ;
}
int
_Py_uop_sym_truthiness(_Py_UopsSymbol *sym)
{
/* There are some non-constant values for
* which `bool(val)` always evaluates to
* True or False, such as tuples with known
* length, but unknown contents, or bound-methods.
* This function will need updating
* should we support those values.
*/
if (_Py_uop_sym_is_bottom(sym)) {
return -1;
}
if (!_Py_uop_sym_is_const(sym)) {
return -1;
}
PyObject *value = _Py_uop_sym_get_const(sym);
if (value == Py_None) {
return 0;
}
/* Only handle a few known safe types */
PyTypeObject *tp = Py_TYPE(value);
if (tp == &PyLong_Type) {
return !_PyLong_IsZero((PyLongObject *)value);
}
if (tp == &PyUnicode_Type) {
return value != &_Py_STR(empty);
}
if (tp == &PyBool_Type) {
return value == Py_True;
}
return -1;
}
// 0 on success, -1 on error.
_Py_UOpsAbstractFrame *
_Py_uop_frame_new(
_Py_UOpsContext *ctx,
PyCodeObject *co,
_Py_UopsSymbol **localsplus_start,
int n_locals_already_filled,
int curr_stackentries)
{
assert(ctx->curr_frame_depth < MAX_ABSTRACT_FRAME_DEPTH);
_Py_UOpsAbstractFrame *frame = &ctx->frames[ctx->curr_frame_depth];
frame->stack_len = co->co_stacksize;
frame->locals_len = co->co_nlocalsplus;
frame->locals = localsplus_start;
frame->stack = frame->locals + co->co_nlocalsplus;
frame->stack_pointer = frame->stack + curr_stackentries;
ctx->n_consumed = localsplus_start + (co->co_nlocalsplus + co->co_stacksize);
if (ctx->n_consumed >= ctx->limit) {
return NULL;
}
// Initialize with the initial state of all local variables
for (int i = n_locals_already_filled; i < co->co_nlocalsplus; i++) {
_Py_UopsSymbol *local = _Py_uop_sym_new_unknown(ctx);
if (local == NULL) {
return NULL;
}
frame->locals[i] = local;
}
// Initialize the stack as well
for (int i = 0; i < curr_stackentries; i++) {
_Py_UopsSymbol *stackvar = _Py_uop_sym_new_unknown(ctx);
if (stackvar == NULL) {
return NULL;
}
frame->stack[i] = stackvar;
}
return frame;
}
void
_Py_uop_abstractcontext_fini(_Py_UOpsContext *ctx)
{
if (ctx == NULL) {
return;
}
ctx->curr_frame_depth = 0;
int tys = ctx->t_arena.ty_curr_number;
for (int i = 0; i < tys; i++) {
Py_CLEAR(ctx->t_arena.arena[i].const_val);
}
}
int
_Py_uop_abstractcontext_init(_Py_UOpsContext *ctx)
{
ctx->limit = ctx->locals_and_stack + MAX_ABSTRACT_INTERP_SIZE;
ctx->n_consumed = ctx->locals_and_stack;
#ifdef Py_DEBUG // Aids debugging a little. There should never be NULL in the abstract interpreter.
for (int i = 0 ; i < MAX_ABSTRACT_INTERP_SIZE; i++) {
ctx->locals_and_stack[i] = NULL;
}
#endif
// Setup the arena for sym expressions.
ctx->t_arena.ty_curr_number = 0;
ctx->t_arena.ty_max_number = TY_ARENA_SIZE;
// Frame setup
ctx->curr_frame_depth = 0;
return 0;
}
int
_Py_uop_frame_pop(_Py_UOpsContext *ctx)
{
_Py_UOpsAbstractFrame *frame = ctx->frame;
ctx->n_consumed = frame->locals;
ctx->curr_frame_depth--;
assert(ctx->curr_frame_depth >= 1);
ctx->frame = &ctx->frames[ctx->curr_frame_depth - 1];
return 0;
}
#define TEST_PREDICATE(PRED, MSG) \
do { \
if (!(PRED)) { \
PyErr_SetString( \
PyExc_AssertionError, \
(MSG)); \
goto fail; \
} \
} while (0)
static _Py_UopsSymbol *
make_bottom(_Py_UOpsContext *ctx)
{
_Py_UopsSymbol *sym = _Py_uop_sym_new_unknown(ctx);
_Py_uop_sym_set_null(sym);
_Py_uop_sym_set_non_null(sym);
return sym;
}
PyObject *
_Py_uop_symbols_test(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(ignored))
{
_Py_UOpsContext context;
_Py_UOpsContext *ctx = &context;
_Py_uop_abstractcontext_init(ctx);
PyObject *val_42 = NULL;
PyObject *val_43 = NULL;
// Use a single 'sym' variable so copy-pasting tests is easier.
_Py_UopsSymbol *sym = _Py_uop_sym_new_unknown(ctx);
if (sym == NULL) {
goto fail;
}
TEST_PREDICATE(!_Py_uop_sym_is_null(sym), "top is NULL");
TEST_PREDICATE(!_Py_uop_sym_is_not_null(sym), "top is not NULL");
TEST_PREDICATE(!_Py_uop_sym_matches_type(sym, &PyLong_Type), "top matches a type");
TEST_PREDICATE(!_Py_uop_sym_is_const(sym), "top is a constant");
TEST_PREDICATE(_Py_uop_sym_get_const(sym) == NULL, "top as constant is not NULL");
TEST_PREDICATE(!_Py_uop_sym_is_bottom(sym), "top is bottom");
sym = make_bottom(ctx);
if (sym == NULL) {
goto fail;
}
TEST_PREDICATE(!_Py_uop_sym_is_null(sym), "bottom is NULL is not false");
TEST_PREDICATE(!_Py_uop_sym_is_not_null(sym), "bottom is not NULL is not false");
TEST_PREDICATE(!_Py_uop_sym_matches_type(sym, &PyLong_Type), "bottom matches a type");
TEST_PREDICATE(!_Py_uop_sym_is_const(sym), "bottom is a constant is not false");
TEST_PREDICATE(_Py_uop_sym_get_const(sym) == NULL, "bottom as constant is not NULL");
TEST_PREDICATE(_Py_uop_sym_is_bottom(sym), "bottom isn't bottom");
sym = _Py_uop_sym_new_type(ctx, &PyLong_Type);
if (sym == NULL) {
goto fail;
}
TEST_PREDICATE(!_Py_uop_sym_is_null(sym), "int is NULL");
TEST_PREDICATE(_Py_uop_sym_is_not_null(sym), "int isn't not NULL");
TEST_PREDICATE(_Py_uop_sym_matches_type(sym, &PyLong_Type), "int isn't int");
TEST_PREDICATE(!_Py_uop_sym_matches_type(sym, &PyFloat_Type), "int matches float");
TEST_PREDICATE(!_Py_uop_sym_is_const(sym), "int is a constant");
TEST_PREDICATE(_Py_uop_sym_get_const(sym) == NULL, "int as constant is not NULL");
_Py_uop_sym_set_type(sym, &PyLong_Type); // Should be a no-op
TEST_PREDICATE(_Py_uop_sym_matches_type(sym, &PyLong_Type), "(int and int) isn't int");
_Py_uop_sym_set_type(sym, &PyFloat_Type); // Should make it bottom
TEST_PREDICATE(_Py_uop_sym_is_bottom(sym), "(int and float) isn't bottom");
val_42 = PyLong_FromLong(42);
assert(val_42 != NULL);
assert(_Py_IsImmortal(val_42));
val_43 = PyLong_FromLong(43);
assert(val_43 != NULL);
assert(_Py_IsImmortal(val_43));
sym = _Py_uop_sym_new_type(ctx, &PyLong_Type);
if (sym == NULL) {
goto fail;
}
_Py_uop_sym_set_const(sym, val_42);
TEST_PREDICATE(_Py_uop_sym_truthiness(sym) == 1, "bool(42) is not True");
TEST_PREDICATE(!_Py_uop_sym_is_null(sym), "42 is NULL");
TEST_PREDICATE(_Py_uop_sym_is_not_null(sym), "42 isn't not NULL");
TEST_PREDICATE(_Py_uop_sym_matches_type(sym, &PyLong_Type), "42 isn't an int");
TEST_PREDICATE(!_Py_uop_sym_matches_type(sym, &PyFloat_Type), "42 matches float");
TEST_PREDICATE(_Py_uop_sym_is_const(sym), "42 is not a constant");
TEST_PREDICATE(_Py_uop_sym_get_const(sym) != NULL, "42 as constant is NULL");
TEST_PREDICATE(_Py_uop_sym_get_const(sym) == val_42, "42 as constant isn't 42");
_Py_uop_sym_set_type(sym, &PyLong_Type); // Should be a no-op
TEST_PREDICATE(_Py_uop_sym_matches_type(sym, &PyLong_Type), "(42 and 42) isn't an int");
TEST_PREDICATE(_Py_uop_sym_get_const(sym) == val_42, "(42 and 42) as constant isn't 42");
_Py_uop_sym_set_type(sym, &PyFloat_Type); // Should make it bottom
TEST_PREDICATE(_Py_uop_sym_is_bottom(sym), "(42 and float) isn't bottom");
sym = _Py_uop_sym_new_type(ctx, &PyLong_Type);
if (sym == NULL) {
goto fail;
}
_Py_uop_sym_set_const(sym, val_42);
_Py_uop_sym_set_const(sym, val_43); // Should make it bottom
TEST_PREDICATE(_Py_uop_sym_is_bottom(sym), "(42 and 43) isn't bottom");
sym = _Py_uop_sym_new_const(ctx, Py_None);
TEST_PREDICATE(_Py_uop_sym_truthiness(sym) == 0, "bool(None) is not False");
sym = _Py_uop_sym_new_const(ctx, Py_False);
TEST_PREDICATE(_Py_uop_sym_truthiness(sym) == 0, "bool(False) is not False");
sym = _Py_uop_sym_new_const(ctx, PyLong_FromLong(0));
TEST_PREDICATE(_Py_uop_sym_truthiness(sym) == 0, "bool(0) is not False");
_Py_uop_abstractcontext_fini(ctx);
Py_DECREF(val_42);
Py_DECREF(val_43);
Py_RETURN_NONE;
fail:
_Py_uop_abstractcontext_fini(ctx);
Py_XDECREF(val_42);
Py_XDECREF(val_43);
return NULL;
}
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