cpython/Python/optimizer_analysis.c at main · Gentle/cpython

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#ifdef _Py_TIER2

* This file contains the support code for CPython's uops optimizer.

* It also performs some simple optimizations.

* It performs a traditional data-flow analysis[1] over the trace of uops.

* Using the information gained, it chooses to emit, or skip certain instructions

* if possible.

* [1] For information on data-flow analysis, please see

* https://clang.llvm.org/docs/DataFlowAnalysisIntro.html

* */

#include "Python.h"

#include "opcode.h"

#include "pycore_dict.h"

#include "pycore_interp.h"

#include "pycore_opcode_metadata.h"

#include "pycore_opcode_utils.h"

#include "pycore_pystate.h" // _PyInterpreterState_GET()

#include "pycore_uop_metadata.h"

#include "pycore_long.h"

#include "pycore_interpframe.h" // _PyFrame_GetCode

#include "pycore_optimizer.h"

#include "pycore_object.h"

#include "pycore_function.h"

#include "pycore_uop_ids.h"

#include "pycore_range.h"

#include "pycore_unicodeobject.h"

#include "pycore_ceval.h"

#include "pycore_floatobject.h"

#include <stdarg.h>

#include <stdbool.h>

#include <stdint.h>

#include <stddef.h>

#ifdef Py_DEBUG

extern const char *_PyUOpName(int index);

extern void _PyUOpPrint(const _PyUOpInstruction *uop);

static const char *const DEBUG_ENV = "PYTHON_OPT_DEBUG";

static inline int get_lltrace(void) {

char *uop_debug = Py_GETENV(DEBUG_ENV);

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 int

get_mutations(PyObject* dict) {

assert(PyDict_CheckExact(dict));

PyDictObject *d = (PyDictObject *)dict;

return (d->_ma_watcher_tag >> DICT_MAX_WATCHERS) & ((1 << DICT_WATCHED_MUTATION_BITS)-1);

}

static void

increment_mutations(PyObject* dict) {

assert(PyDict_CheckExact(dict));

PyDictObject *d = (PyDictObject *)dict;

d->_ma_watcher_tag += (1 << DICT_MAX_WATCHERS);

}

/* The first two dict watcher IDs are reserved for CPython,

* so we don't need to check that they haven't been used */

#define BUILTINS_WATCHER_ID 0

#define GLOBALS_WATCHER_ID 1

#define TYPE_WATCHER_ID 0

static int

globals_watcher_callback(PyDict_WatchEvent event, PyObject* dict,

PyObject* key, PyObject* new_value)

{

RARE_EVENT_STAT_INC(watched_globals_modification);

assert(get_mutations(dict) < _Py_MAX_ALLOWED_GLOBALS_MODIFICATIONS);

_Py_Executors_InvalidateDependency(_PyInterpreterState_GET(), dict, 1);

increment_mutations(dict);

PyDict_Unwatch(GLOBALS_WATCHER_ID, dict);

return 0;

}

static int

type_watcher_callback(PyTypeObject* type)

{

_Py_Executors_InvalidateDependency(_PyInterpreterState_GET(), type, 1);

PyType_Unwatch(TYPE_WATCHER_ID, (PyObject *)type);

return 0;

}

static PyObject *

convert_global_to_const(_PyUOpInstruction *inst, PyObject *obj, bool pop)

{

assert(inst->opcode == _LOAD_GLOBAL_MODULE || inst->opcode == _LOAD_GLOBAL_BUILTINS || inst->opcode == _LOAD_ATTR_MODULE);

assert(PyDict_CheckExact(obj));

PyDictObject *dict = (PyDictObject *)obj;

assert(dict->ma_keys->dk_kind == DICT_KEYS_UNICODE);

PyDictUnicodeEntry *entries = DK_UNICODE_ENTRIES(dict->ma_keys);

int64_t index = inst->operand1;

assert(index <= UINT16_MAX);

if ((int)index >= dict->ma_keys->dk_nentries) {

return NULL;

}

PyDictKeysObject *keys = dict->ma_keys;

if (keys->dk_version != inst->operand0) {

return NULL;

}

PyObject *res = entries[index].me_value;

if (res == NULL) {

return NULL;

}

if (_Py_IsImmortal(res)) {

inst->opcode = pop ? _POP_TOP_LOAD_CONST_INLINE_BORROW : _LOAD_CONST_INLINE_BORROW;

}

else {

inst->opcode = pop ? _POP_TOP_LOAD_CONST_INLINE : _LOAD_CONST_INLINE;

}

if (inst->oparg & 1) {

assert(inst[1].opcode == _PUSH_NULL_CONDITIONAL);

assert(inst[1].oparg & 1);

}

inst->operand0 = (uint64_t)res;

return res;

}

static bool

incorrect_keys(PyObject *obj, uint32_t version)

{

if (!PyDict_CheckExact(obj)) {

return true;

}

PyDictObject *dict = (PyDictObject *)obj;

return dict->ma_keys->dk_version != version;

}

#define STACK_LEVEL() ((int)(stack_pointer - ctx->frame->stack))

#define STACK_SIZE() ((int)(ctx->frame->stack_len))

#define WITHIN_STACK_BOUNDS() \

(STACK_LEVEL() >= 0 && STACK_LEVEL() <= STACK_SIZE())

#define GETLOCAL(idx) ((ctx->frame->locals[idx]))

#define REPLACE_OP(INST, OP, ARG, OPERAND) \

(INST)->opcode = OP; \

(INST)->oparg = ARG; \

(INST)->operand0 = OPERAND;

/* Shortened forms for convenience, used in optimizer_bytecodes.c */

#define sym_is_not_null _Py_uop_sym_is_not_null

#define sym_is_const _Py_uop_sym_is_const

#define sym_is_safe_const _Py_uop_sym_is_safe_const

#define sym_get_const _Py_uop_sym_get_const

#define sym_new_const_steal _Py_uop_sym_new_const_steal

#define sym_get_const_as_stackref _Py_uop_sym_get_const_as_stackref

#define sym_new_unknown _Py_uop_sym_new_unknown

#define sym_new_not_null _Py_uop_sym_new_not_null

#define sym_new_type _Py_uop_sym_new_type

#define sym_is_null _Py_uop_sym_is_null

#define sym_new_const _Py_uop_sym_new_const

#define sym_new_null _Py_uop_sym_new_null

#define sym_has_type _Py_uop_sym_has_type

#define sym_get_type _Py_uop_sym_get_type

#define sym_matches_type _Py_uop_sym_matches_type

#define sym_matches_type_version _Py_uop_sym_matches_type_version

#define sym_set_null(SYM) _Py_uop_sym_set_null(ctx, SYM)

#define sym_set_non_null(SYM) _Py_uop_sym_set_non_null(ctx, SYM)

#define sym_set_type(SYM, TYPE) _Py_uop_sym_set_type(ctx, SYM, TYPE)

#define sym_set_type_version(SYM, VERSION) _Py_uop_sym_set_type_version(ctx, SYM, VERSION)

#define sym_set_const(SYM, CNST) _Py_uop_sym_set_const(ctx, SYM, CNST)

#define sym_set_compact_int(SYM) _Py_uop_sym_set_compact_int(ctx, SYM)

#define sym_is_bottom _Py_uop_sym_is_bottom

#define sym_truthiness _Py_uop_sym_truthiness

#define frame_new _Py_uop_frame_new

#define frame_pop _Py_uop_frame_pop

#define sym_new_tuple _Py_uop_sym_new_tuple

#define sym_tuple_getitem _Py_uop_sym_tuple_getitem

#define sym_tuple_length _Py_uop_sym_tuple_length

#define sym_is_immortal _Py_uop_symbol_is_immortal

#define sym_is_compact_int _Py_uop_sym_is_compact_int

#define sym_new_compact_int _Py_uop_sym_new_compact_int

#define sym_new_truthiness _Py_uop_sym_new_truthiness

#define JUMP_TO_LABEL(label) goto label;

static int

optimize_to_bool(

_PyUOpInstruction *this_instr,

JitOptContext *ctx,

JitOptRef value,

JitOptRef *result_ptr)

{

if (sym_matches_type(value, &PyBool_Type)) {

REPLACE_OP(this_instr, _NOP, 0, 0);

*result_ptr = value;

return 1;

}

int truthiness = sym_truthiness(ctx, value);

if (truthiness >= 0) {

PyObject *load = truthiness ? Py_True : Py_False;

REPLACE_OP(this_instr, _POP_TOP_LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)load);

*result_ptr = sym_new_const(ctx, load);

return 1;

}

return 0;

}

static void

eliminate_pop_guard(_PyUOpInstruction *this_instr, bool exit)

{

REPLACE_OP(this_instr, _POP_TOP, 0, 0);

if (exit) {

REPLACE_OP((this_instr+1), _EXIT_TRACE, 0, 0);

this_instr[1].target = this_instr->target;

}

static JitOptRef

lookup_attr(JitOptContext *ctx, _PyUOpInstruction *this_instr,

PyTypeObject *type, PyObject *name, uint16_t immortal,

uint16_t mortal)

{

// The cached value may be dead, so we need to do the lookup again... :(

if (type && PyType_Check(type)) {

PyObject *lookup = _PyType_Lookup(type, name);

if (lookup) {

int opcode = _Py_IsImmortal(lookup) ? immortal : mortal;

REPLACE_OP(this_instr, opcode, 0, (uintptr_t)lookup);

return sym_new_const(ctx, lookup);

}

return sym_new_not_null(ctx);

}

static PyCodeObject *

get_code_with_logging(_PyUOpInstruction *op)

{

PyCodeObject *co = NULL;

uint64_t push_operand = op->operand0;

if (push_operand & 1) {

co = (PyCodeObject *)(push_operand & ~1);

DPRINTF(3, "code=%p ", co);

assert(PyCode_Check(co));

}

else {

PyFunctionObject *func = (PyFunctionObject *)push_operand;

DPRINTF(3, "func=%p ", func);

if (func == NULL) {

DPRINTF(3, "\n");

DPRINTF(1, "Missing function\n");

return NULL;

}

co = (PyCodeObject *)func->func_code;

DPRINTF(3, "code=%p ", co);

}

return co;

}

static

PyCodeObject *

get_current_code_object(JitOptContext *ctx)

{

return (PyCodeObject *)ctx->frame->func->func_code;

}

static PyObject *

get_co_name(JitOptContext *ctx, int index)

{

return PyTuple_GET_ITEM(get_current_code_object(ctx)->co_names, index);

}

// TODO (gh-134584) generate most of this table automatically

const uint16_t op_without_decref_inputs[MAX_UOP_ID + 1] = {

[_BINARY_OP_MULTIPLY_FLOAT] = _BINARY_OP_MULTIPLY_FLOAT__NO_DECREF_INPUTS,

[_BINARY_OP_ADD_FLOAT] = _BINARY_OP_ADD_FLOAT__NO_DECREF_INPUTS,

[_BINARY_OP_SUBTRACT_FLOAT] = _BINARY_OP_SUBTRACT_FLOAT__NO_DECREF_INPUTS,

};

/* >0 (length) for success, 0 for not ready, clears all possible errors. */

static int

optimize_uops(

PyFunctionObject *func,

_PyUOpInstruction *trace,

int trace_len,

int curr_stacklen,

_PyBloomFilter *dependencies

)

{

assert(!PyErr_Occurred());

JitOptContext context;

JitOptContext *ctx = &context;

uint32_t opcode = UINT16_MAX;

int curr_space = 0;

int max_space = 0;

_PyUOpInstruction *first_valid_check_stack = NULL;

_PyUOpInstruction *corresponding_check_stack = NULL;

// Make sure that watchers are set up

PyInterpreterState *interp = _PyInterpreterState_GET();

if (interp->dict_state.watchers[GLOBALS_WATCHER_ID] == NULL) {

interp->dict_state.watchers[GLOBALS_WATCHER_ID] = globals_watcher_callback;

interp->type_watchers[TYPE_WATCHER_ID] = type_watcher_callback;

}

_Py_uop_abstractcontext_init(ctx);

_Py_UOpsAbstractFrame *frame = _Py_uop_frame_new(ctx, (PyCodeObject *)func->func_code, curr_stacklen, NULL, 0);

if (frame == NULL) {

return 0;

}

frame->func = func;

ctx->curr_frame_depth++;

ctx->frame = frame;

_PyUOpInstruction *this_instr = NULL;

for (int i = 0; !ctx->done; i++) {

assert(i < trace_len);

this_instr = &trace[i];

int oparg = this_instr->oparg;

opcode = this_instr->opcode;

JitOptRef *stack_pointer = ctx->frame->stack_pointer;

#ifdef Py_DEBUG

if (get_lltrace() >= 3) {

printf("%4d abs: ", (int)(this_instr - trace));

_PyUOpPrint(this_instr);

printf(" ");

}

#endif

switch (opcode) {

#include "optimizer_cases.c.h"

default:

DPRINTF(1, "\nUnknown opcode in abstract interpreter\n");

Py_UNREACHABLE();

}

assert(ctx->frame != NULL);

DPRINTF(3, " stack_level %d\n", STACK_LEVEL());

ctx->frame->stack_pointer = stack_pointer;

assert(STACK_LEVEL() >= 0);

}

if (ctx->out_of_space) {

DPRINTF(3, "\n");

DPRINTF(1, "Out of space in abstract interpreter\n");

}

if (ctx->contradiction) {

// Attempted to push a "bottom" (contradiction) symbol onto the stack.

// This means that the abstract interpreter has hit unreachable code.

// We *could* generate an _EXIT_TRACE or _FATAL_ERROR here, but hitting

// bottom indicates type instability, so we are probably better off

// retrying later.

DPRINTF(3, "\n");

DPRINTF(1, "Hit bottom in abstract interpreter\n");

_Py_uop_abstractcontext_fini(ctx);

return 0;

}

/* Either reached the end or cannot optimize further, but there

* would be no benefit in retrying later */

_Py_uop_abstractcontext_fini(ctx);

if (first_valid_check_stack != NULL) {

assert(first_valid_check_stack->opcode == _CHECK_STACK_SPACE);

assert(max_space > 0);

assert(max_space <= INT_MAX);

assert(max_space <= INT32_MAX);

first_valid_check_stack->opcode = _CHECK_STACK_SPACE_OPERAND;

first_valid_check_stack->operand0 = max_space;

}

return trace_len;

error:

DPRINTF(3, "\n");

DPRINTF(1, "Encountered error in abstract interpreter\n");

if (opcode <= MAX_UOP_ID) {

OPT_ERROR_IN_OPCODE(opcode);

}

_Py_uop_abstractcontext_fini(ctx);

assert(PyErr_Occurred());

PyErr_Clear();

return 0;

}

const uint16_t op_without_push[MAX_UOP_ID + 1] = {

[_COPY] = _NOP,

[_LOAD_CONST_INLINE] = _NOP,

[_LOAD_CONST_INLINE_BORROW] = _NOP,

[_LOAD_CONST_UNDER_INLINE] = _POP_TOP_LOAD_CONST_INLINE,

[_LOAD_CONST_UNDER_INLINE_BORROW] = _POP_TOP_LOAD_CONST_INLINE_BORROW,

[_LOAD_FAST] = _NOP,

[_LOAD_FAST_BORROW] = _NOP,

[_LOAD_SMALL_INT] = _NOP,

[_POP_TOP_LOAD_CONST_INLINE] = _POP_TOP,

[_POP_TOP_LOAD_CONST_INLINE_BORROW] = _POP_TOP,

[_POP_TWO_LOAD_CONST_INLINE_BORROW] = _POP_TWO,

[_POP_CALL_TWO_LOAD_CONST_INLINE_BORROW] = _POP_CALL_TWO,

};

const bool op_skip[MAX_UOP_ID + 1] = {

[_NOP] = true,

[_CHECK_VALIDITY] = true,

[_CHECK_PERIODIC] = true,

[_SET_IP] = true,

};

const uint16_t op_without_pop[MAX_UOP_ID + 1] = {

[_POP_TOP] = _NOP,

[_POP_TOP_LOAD_CONST_INLINE] = _LOAD_CONST_INLINE,

[_POP_TOP_LOAD_CONST_INLINE_BORROW] = _LOAD_CONST_INLINE_BORROW,

[_POP_TWO] = _POP_TOP,

[_POP_TWO_LOAD_CONST_INLINE_BORROW] = _POP_TOP_LOAD_CONST_INLINE_BORROW,

[_POP_CALL_TWO_LOAD_CONST_INLINE_BORROW] = _POP_CALL_ONE_LOAD_CONST_INLINE_BORROW,

[_POP_CALL_ONE_LOAD_CONST_INLINE_BORROW] = _POP_CALL_LOAD_CONST_INLINE_BORROW,

[_POP_CALL_TWO] = _POP_CALL_ONE,

[_POP_CALL_ONE] = _POP_CALL,

};

const uint16_t op_without_pop_null[MAX_UOP_ID + 1] = {

[_POP_CALL] = _POP_TOP,

[_POP_CALL_LOAD_CONST_INLINE_BORROW] = _POP_TOP_LOAD_CONST_INLINE_BORROW,

};

static int

remove_unneeded_uops(_PyUOpInstruction *buffer, int buffer_size)

{

/* Remove _SET_IP and _CHECK_VALIDITY where possible.

* _SET_IP is needed if the following instruction escapes or

* could error. _CHECK_VALIDITY is needed if the previous

* instruction could have escaped. */

int last_set_ip = -1;

bool may_have_escaped = true;

for (int pc = 0; pc < buffer_size; pc++) {

int opcode = buffer[pc].opcode;

switch (opcode) {

case _START_EXECUTOR:

may_have_escaped = false;

break;

case _SET_IP:

buffer[pc].opcode = _NOP;

last_set_ip = pc;

break;

case _CHECK_VALIDITY:

if (may_have_escaped) {

may_have_escaped = false;

}

else {

buffer[pc].opcode = _NOP;

}

break;

default:

{

// Cancel out pushes and pops, repeatedly. So:

// _LOAD_FAST + _POP_TWO_LOAD_CONST_INLINE_BORROW + _POP_TOP

// ...becomes:

// _NOP + _POP_TOP + _NOP

while (op_without_pop[opcode] || op_without_pop_null[opcode]) {

_PyUOpInstruction *last = &buffer[pc - 1];

while (op_skip[last->opcode]) {

last--;

}

if (op_without_push[last->opcode] && op_without_pop[opcode]) {

last->opcode = op_without_push[last->opcode];

opcode = buffer[pc].opcode = op_without_pop[opcode];

if (op_without_pop[last->opcode]) {

opcode = last->opcode;

pc = (int)(last - buffer);

}

else if (last->opcode == _PUSH_NULL) {

// Handle _POP_CALL and _POP_CALL_LOAD_CONST_INLINE_BORROW separately.

// This looks for a preceding _PUSH_NULL instruction and

// simplifies to _POP_TOP(_LOAD_CONST_INLINE_BORROW).

last->opcode = _NOP;

opcode = buffer[pc].opcode = op_without_pop_null[opcode];

assert(opcode);

}

else {

break;

}

/* _PUSH_FRAME doesn't escape or error, but it

* does need the IP for the return address */

bool needs_ip = opcode == _PUSH_FRAME;

if (_PyUop_Flags[opcode] & HAS_ESCAPES_FLAG) {

needs_ip = true;

may_have_escaped = true;

}

if (needs_ip && last_set_ip >= 0) {

assert(buffer[last_set_ip].opcode == _NOP);

buffer[last_set_ip].opcode = _SET_IP;

last_set_ip = -1;

}

break;

}

case _JUMP_TO_TOP:

case _EXIT_TRACE:

return pc + 1;

}

Py_UNREACHABLE();

}

// 0 - failure, no error raised, just fall back to Tier 1

// -1 - failure, and raise error

// > 0 - length of optimized trace

int

_Py_uop_analyze_and_optimize(

_PyInterpreterFrame *frame,

_PyUOpInstruction *buffer,

int length,

int curr_stacklen,

_PyBloomFilter *dependencies

)

{

OPT_STAT_INC(optimizer_attempts);

length = optimize_uops(

_PyFrame_GetFunction(frame), buffer,

length, curr_stacklen, dependencies);

if (length == 0) {

return length;

}

assert(length > 0);

length = remove_unneeded_uops(buffer, length);

assert(length > 0);

OPT_STAT_INC(optimizer_successes);

return length;

}

#endif /* _Py_TIER2 */

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