cpython/Python/assemble.c at 362cd2680b45a36c3467b9721ff7fc0ceb338452 · python/cpython · GitHub

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#include <stdbool.h>

#include "Python.h"

#include "pycore_code.h" // write_location_entry_start()

#include "pycore_compile.h"

#include "pycore_instruction_sequence.h"

#include "pycore_opcode_utils.h" // IS_BACKWARDS_JUMP_OPCODE

#include "pycore_opcode_metadata.h" // is_pseudo_target, _PyOpcode_Caches

#include "pycore_symtable.h" // _Py_SourceLocation

#define DEFAULT_CODE_SIZE 128

#define DEFAULT_LNOTAB_SIZE 16

#define DEFAULT_CNOTAB_SIZE 32

#undef SUCCESS

#undef ERROR

#define SUCCESS 0

#define ERROR -1

#define RETURN_IF_ERROR(X) \

if ((X) < 0) { \

return ERROR; \

}

typedef _Py_SourceLocation location;

typedef _PyInstruction instruction;

typedef _PyInstructionSequence instr_sequence;

static inline bool

same_location(location a, location b)

{

return a.lineno == b.lineno &&

a.end_lineno == b.end_lineno &&

a.col_offset == b.col_offset &&

a.end_col_offset == b.end_col_offset;

}

static int

instr_size(instruction *instr)

{

int opcode = instr->i_opcode;

int oparg = instr->i_oparg;

assert(!IS_PSEUDO_INSTR(opcode));

assert(OPCODE_HAS_ARG(opcode) || oparg == 0);

int extended_args = (0xFFFFFF < oparg) + (0xFFFF < oparg) + (0xFF < oparg);

int caches = _PyOpcode_Caches[opcode];

return extended_args + 1 + caches;

}

struct assembler {

PyObject *a_bytecode; /* bytes containing bytecode */

int a_offset; /* offset into bytecode */

PyObject *a_except_table; /* bytes containing exception table */

int a_except_table_off; /* offset into exception table */

/* Location Info */

int a_lineno; /* lineno of last emitted instruction */

PyObject* a_linetable; /* bytes containing location info */

int a_location_off; /* offset of last written location info frame */

};

static int

assemble_init(struct assembler *a, int firstlineno)

{

memset(a, 0, sizeof(struct assembler));

a->a_lineno = firstlineno;

a->a_linetable = NULL;

a->a_location_off = 0;

a->a_except_table = NULL;

a->a_bytecode = PyBytes_FromStringAndSize(NULL, DEFAULT_CODE_SIZE);

if (a->a_bytecode == NULL) {

goto error;

}

a->a_linetable = PyBytes_FromStringAndSize(NULL, DEFAULT_CNOTAB_SIZE);

if (a->a_linetable == NULL) {

goto error;

}

a->a_except_table = PyBytes_FromStringAndSize(NULL, DEFAULT_LNOTAB_SIZE);

if (a->a_except_table == NULL) {

goto error;

}

return SUCCESS;

error:

Py_XDECREF(a->a_bytecode);

Py_XDECREF(a->a_linetable);

Py_XDECREF(a->a_except_table);

return ERROR;

}

static void

assemble_free(struct assembler *a)

{

Py_XDECREF(a->a_bytecode);

Py_XDECREF(a->a_linetable);

Py_XDECREF(a->a_except_table);

}

static inline void

write_except_byte(struct assembler *a, int byte) {

unsigned char *p = (unsigned char *) PyBytes_AS_STRING(a->a_except_table);

p[a->a_except_table_off++] = byte;

}

#define CONTINUATION_BIT 64

static void

assemble_emit_exception_table_item(struct assembler *a, int value, int msb)

{

assert ((msb | 128) == 128);

assert(value >= 0 && value < (1 << 30));

if (value >= 1 << 24) {

write_except_byte(a, (value >> 24) | CONTINUATION_BIT | msb);

msb = 0;

}

if (value >= 1 << 18) {

write_except_byte(a, ((value >> 18)&0x3f) | CONTINUATION_BIT | msb);

msb = 0;

}

if (value >= 1 << 12) {

write_except_byte(a, ((value >> 12)&0x3f) | CONTINUATION_BIT | msb);

msb = 0;

}

if (value >= 1 << 6) {

write_except_byte(a, ((value >> 6)&0x3f) | CONTINUATION_BIT | msb);

msb = 0;

}

write_except_byte(a, (value&0x3f) | msb);

}

/* See Objects/exception_handling_notes.txt for details of layout */

#define MAX_SIZE_OF_ENTRY 20

static int

assemble_emit_exception_table_entry(struct assembler *a, int start, int end,

int handler_offset,

_PyExceptHandlerInfo *handler)

{

Py_ssize_t len = PyBytes_GET_SIZE(a->a_except_table);

if (a->a_except_table_off + MAX_SIZE_OF_ENTRY >= len) {

RETURN_IF_ERROR(_PyBytes_Resize(&a->a_except_table, len * 2));

}

int size = end-start;

assert(end > start);

int target = handler_offset;

int depth = handler->h_startdepth - 1;

if (handler->h_preserve_lasti > 0) {

depth -= 1;

}

assert(depth >= 0);

int depth_lasti = (depth<<1) | handler->h_preserve_lasti;

assemble_emit_exception_table_item(a, start, (1<<7));

assemble_emit_exception_table_item(a, size, 0);

assemble_emit_exception_table_item(a, target, 0);

assemble_emit_exception_table_item(a, depth_lasti, 0);

return SUCCESS;

}

static int

assemble_exception_table(struct assembler *a, instr_sequence *instrs)

{

int ioffset = 0;

_PyExceptHandlerInfo handler;

handler.h_label = -1;

handler.h_startdepth = -1;

handler.h_preserve_lasti = -1;

int start = -1;

for (int i = 0; i < instrs->s_used; i++) {

instruction *instr = &instrs->s_instrs[i];

if (instr->i_except_handler_info.h_label != handler.h_label) {

if (handler.h_label >= 0) {

int handler_offset = instrs->s_instrs[handler.h_label].i_offset;

RETURN_IF_ERROR(

assemble_emit_exception_table_entry(a, start, ioffset,

handler_offset,

&handler));

}

start = ioffset;

handler = instr->i_except_handler_info;

}

ioffset += instr_size(instr);

}

if (handler.h_label >= 0) {

int handler_offset = instrs->s_instrs[handler.h_label].i_offset;

RETURN_IF_ERROR(assemble_emit_exception_table_entry(a, start, ioffset,

handler_offset,

&handler));

}

return SUCCESS;

}

/* Code location emitting code. See locations.md for a description of the format. */

#define MSB 0x80

static void

write_location_byte(struct assembler* a, int val)

{

PyBytes_AS_STRING(a->a_linetable)[a->a_location_off] = val&255;

a->a_location_off++;

}

static uint8_t *

location_pointer(struct assembler* a)

{

return (uint8_t *)PyBytes_AS_STRING(a->a_linetable) +

a->a_location_off;

}

static void

write_location_first_byte(struct assembler* a, int code, int length)

{

a->a_location_off += write_location_entry_start(

location_pointer(a), code, length);

}

static void

write_location_varint(struct assembler* a, unsigned int val)

{

uint8_t *ptr = location_pointer(a);

a->a_location_off += write_varint(ptr, val);

}

static void

write_location_signed_varint(struct assembler* a, int val)

{

uint8_t *ptr = location_pointer(a);

a->a_location_off += write_signed_varint(ptr, val);

}

static void

write_location_info_short_form(struct assembler* a, int length, int column, int end_column)

{

assert(length > 0 && length <= 8);

int column_low_bits = column & 7;

int column_group = column >> 3;

assert(column < 80);

assert(end_column >= column);

assert(end_column - column < 16);

write_location_first_byte(a, PY_CODE_LOCATION_INFO_SHORT0 + column_group, length);

write_location_byte(a, (column_low_bits << 4) | (end_column - column));

}

static void

write_location_info_oneline_form(struct assembler* a, int length, int line_delta, int column, int end_column)

{

assert(length > 0 && length <= 8);

assert(line_delta >= 0 && line_delta < 3);

assert(column < 128);

assert(end_column < 128);

write_location_first_byte(a, PY_CODE_LOCATION_INFO_ONE_LINE0 + line_delta, length);

write_location_byte(a, column);

write_location_byte(a, end_column);

}

static void

write_location_info_long_form(struct assembler* a, location loc, int length)

{

assert(length > 0 && length <= 8);

write_location_first_byte(a, PY_CODE_LOCATION_INFO_LONG, length);

write_location_signed_varint(a, loc.lineno - a->a_lineno);

assert(loc.end_lineno >= loc.lineno);

write_location_varint(a, loc.end_lineno - loc.lineno);

write_location_varint(a, loc.col_offset + 1);

write_location_varint(a, loc.end_col_offset + 1);

}

static void

write_location_info_none(struct assembler* a, int length)

{

write_location_first_byte(a, PY_CODE_LOCATION_INFO_NONE, length);

}

static void

write_location_info_no_column(struct assembler* a, int length, int line_delta)

{

write_location_first_byte(a, PY_CODE_LOCATION_INFO_NO_COLUMNS, length);

write_location_signed_varint(a, line_delta);

}

#define THEORETICAL_MAX_ENTRY_SIZE 25 /* 1 + 6 + 6 + 6 + 6 */

static int

write_location_info_entry(struct assembler* a, location loc, int isize)

{

Py_ssize_t len = PyBytes_GET_SIZE(a->a_linetable);

if (a->a_location_off + THEORETICAL_MAX_ENTRY_SIZE >= len) {

assert(len > THEORETICAL_MAX_ENTRY_SIZE);

RETURN_IF_ERROR(_PyBytes_Resize(&a->a_linetable, len*2));

}

if (loc.lineno < 0) {

write_location_info_none(a, isize);

return SUCCESS;

}

int line_delta = loc.lineno - a->a_lineno;

int column = loc.col_offset;

int end_column = loc.end_col_offset;

assert(column >= -1);

assert(end_column >= -1);

if (column < 0 || end_column < 0) {

if (loc.end_lineno == loc.lineno || loc.end_lineno == -1) {

write_location_info_no_column(a, isize, line_delta);

a->a_lineno = loc.lineno;

return SUCCESS;

}

else if (loc.end_lineno == loc.lineno) {

if (line_delta == 0 && column < 80 && end_column - column < 16 && end_column >= column) {

write_location_info_short_form(a, isize, column, end_column);

return SUCCESS;

}

if (line_delta >= 0 && line_delta < 3 && column < 128 && end_column < 128) {

write_location_info_oneline_form(a, isize, line_delta, column, end_column);

a->a_lineno = loc.lineno;

return SUCCESS;

}

write_location_info_long_form(a, loc, isize);

a->a_lineno = loc.lineno;

return SUCCESS;

}

static int

assemble_emit_location(struct assembler* a, location loc, int isize)

{

if (isize == 0) {

return SUCCESS;

}

while (isize > 8) {

RETURN_IF_ERROR(write_location_info_entry(a, loc, 8));

isize -= 8;

}

return write_location_info_entry(a, loc, isize);

}

static int

assemble_location_info(struct assembler *a, instr_sequence *instrs,

int firstlineno)

{

a->a_lineno = firstlineno;

location loc = NO_LOCATION;

int size = 0;

for (int i = 0; i < instrs->s_used; i++) {

instruction *instr = &instrs->s_instrs[i];

if (!same_location(loc, instr->i_loc)) {

RETURN_IF_ERROR(assemble_emit_location(a, loc, size));

loc = instr->i_loc;

size = 0;

}

size += instr_size(instr);

}

RETURN_IF_ERROR(assemble_emit_location(a, loc, size));

return SUCCESS;

}

static void

write_instr(_Py_CODEUNIT *codestr, instruction *instr, int ilen)

{

int opcode = instr->i_opcode;

assert(!IS_PSEUDO_INSTR(opcode));

int oparg = instr->i_oparg;

assert(OPCODE_HAS_ARG(opcode) || oparg == 0);

int caches = _PyOpcode_Caches[opcode];

switch (ilen - caches) {

case 4:

codestr->op.code = EXTENDED_ARG;

codestr->op.arg = (oparg >> 24) & 0xFF;

codestr++;

/* fall through */

case 3:

codestr->op.code = EXTENDED_ARG;

codestr->op.arg = (oparg >> 16) & 0xFF;

codestr++;

/* fall through */

case 2:

codestr->op.code = EXTENDED_ARG;

codestr->op.arg = (oparg >> 8) & 0xFF;

codestr++;

/* fall through */

case 1:

codestr->op.code = opcode;

codestr->op.arg = oparg & 0xFF;

codestr++;

break;

default:

Py_UNREACHABLE();

}

while (caches--) {

codestr->op.code = CACHE;

codestr->op.arg = 0;

codestr++;

}

/* assemble_emit_instr()

Extend the bytecode with a new instruction.

Update lnotab if necessary.

static int

assemble_emit_instr(struct assembler *a, instruction *instr)

{

Py_ssize_t len = PyBytes_GET_SIZE(a->a_bytecode);

_Py_CODEUNIT *code;

int size = instr_size(instr);

if (a->a_offset + size >= len / (int)sizeof(_Py_CODEUNIT)) {

if (len > PY_SSIZE_T_MAX / 2) {

return ERROR;

}

RETURN_IF_ERROR(_PyBytes_Resize(&a->a_bytecode, len * 2));

}

code = (_Py_CODEUNIT *)PyBytes_AS_STRING(a->a_bytecode) + a->a_offset;

a->a_offset += size;

write_instr(code, instr, size);

return SUCCESS;

}

static int

assemble_emit(struct assembler *a, instr_sequence *instrs,

int first_lineno, PyObject *const_cache)

{

RETURN_IF_ERROR(assemble_init(a, first_lineno));

for (int i = 0; i < instrs->s_used; i++) {

instruction *instr = &instrs->s_instrs[i];

RETURN_IF_ERROR(assemble_emit_instr(a, instr));

}

RETURN_IF_ERROR(assemble_location_info(a, instrs, a->a_lineno));

RETURN_IF_ERROR(assemble_exception_table(a, instrs));

RETURN_IF_ERROR(_PyBytes_Resize(&a->a_except_table, a->a_except_table_off));

RETURN_IF_ERROR(_PyCompile_ConstCacheMergeOne(const_cache, &a->a_except_table));

RETURN_IF_ERROR(_PyBytes_Resize(&a->a_linetable, a->a_location_off));

RETURN_IF_ERROR(_PyCompile_ConstCacheMergeOne(const_cache, &a->a_linetable));

RETURN_IF_ERROR(_PyBytes_Resize(&a->a_bytecode, a->a_offset * sizeof(_Py_CODEUNIT)));

RETURN_IF_ERROR(_PyCompile_ConstCacheMergeOne(const_cache, &a->a_bytecode));

return SUCCESS;

}

static PyObject *

dict_keys_inorder(PyObject *dict, Py_ssize_t offset)

{

PyObject *tuple, *k, *v;

Py_ssize_t pos = 0, size = PyDict_GET_SIZE(dict);

tuple = PyTuple_New(size);

if (tuple == NULL)

return NULL;

while (PyDict_Next(dict, &pos, &k, &v)) {

Py_ssize_t i = PyLong_AsSsize_t(v);

if (i == -1 && PyErr_Occurred()) {

Py_DECREF(tuple);

return NULL;

}

assert((i - offset) < size);

assert((i - offset) >= 0);

PyTuple_SET_ITEM(tuple, i - offset, Py_NewRef(k));

}

return tuple;

}

// This is in codeobject.c.

extern void _Py_set_localsplus_info(int, PyObject *, unsigned char,

PyObject *, PyObject *);

static int

compute_localsplus_info(_PyCompile_CodeUnitMetadata *umd, int nlocalsplus,

PyObject *names, PyObject *kinds)

{

PyObject *k, *v;

Py_ssize_t pos = 0;

while (PyDict_Next(umd->u_varnames, &pos, &k, &v)) {

int offset = PyLong_AsInt(v);

if (offset == -1 && PyErr_Occurred()) {

return ERROR;

}

assert(offset >= 0);

assert(offset < nlocalsplus);

// For now we do not distinguish arg kinds.

_PyLocals_Kind kind = CO_FAST_LOCAL;

int has_key = PyDict_Contains(umd->u_fasthidden, k);

RETURN_IF_ERROR(has_key);

if (has_key) {

kind |= CO_FAST_HIDDEN;

}

has_key = PyDict_Contains(umd->u_cellvars, k);

RETURN_IF_ERROR(has_key);

if (has_key) {

kind |= CO_FAST_CELL;

}

_Py_set_localsplus_info(offset, k, kind, names, kinds);

}

int nlocals = (int)PyDict_GET_SIZE(umd->u_varnames);

// This counter mirrors the fix done in fix_cell_offsets().

int numdropped = 0;

pos = 0;

while (PyDict_Next(umd->u_cellvars, &pos, &k, &v)) {

int has_name = PyDict_Contains(umd->u_varnames, k);

RETURN_IF_ERROR(has_name);

if (has_name) {

// Skip cells that are already covered by locals.

numdropped += 1;

continue;

}

int offset = PyLong_AsInt(v);

if (offset == -1 && PyErr_Occurred()) {

return ERROR;

}

assert(offset >= 0);

offset += nlocals - numdropped;

assert(offset < nlocalsplus);

_Py_set_localsplus_info(offset, k, CO_FAST_CELL, names, kinds);

}

pos = 0;

while (PyDict_Next(umd->u_freevars, &pos, &k, &v)) {

int offset = PyLong_AsInt(v);

if (offset == -1 && PyErr_Occurred()) {

return ERROR;

}

assert(offset >= 0);

offset += nlocals - numdropped;

assert(offset < nlocalsplus);

_Py_set_localsplus_info(offset, k, CO_FAST_FREE, names, kinds);

}

return SUCCESS;

}

static PyCodeObject *

makecode(_PyCompile_CodeUnitMetadata *umd, struct assembler *a, PyObject *const_cache,

PyObject *constslist, int maxdepth, int nlocalsplus, int code_flags,

PyObject *filename)

{

PyCodeObject *co = NULL;

PyObject *names = NULL;

PyObject *consts = NULL;

PyObject *localsplusnames = NULL;

PyObject *localspluskinds = NULL;

names = dict_keys_inorder(umd->u_names, 0);

if (!names) {

goto error;

}

if (_PyCompile_ConstCacheMergeOne(const_cache, &names) < 0) {

goto error;

}

consts = PyList_AsTuple(constslist); /* PyCode_New requires a tuple */

if (consts == NULL) {

goto error;

}

if (_PyCompile_ConstCacheMergeOne(const_cache, &consts) < 0) {

goto error;

}

assert(umd->u_posonlyargcount < INT_MAX);

assert(umd->u_argcount < INT_MAX);

assert(umd->u_kwonlyargcount < INT_MAX);

int posonlyargcount = (int)umd->u_posonlyargcount;

int posorkwargcount = (int)umd->u_argcount;

assert(INT_MAX - posonlyargcount - posorkwargcount > 0);

int kwonlyargcount = (int)umd->u_kwonlyargcount;

localsplusnames = PyTuple_New(nlocalsplus);

if (localsplusnames == NULL) {

goto error;

}

localspluskinds = PyBytes_FromStringAndSize(NULL, nlocalsplus);

if (localspluskinds == NULL) {

goto error;

}

if (compute_localsplus_info(umd, nlocalsplus,

localsplusnames, localspluskinds) == ERROR) {

goto error;

}

struct _PyCodeConstructor con = {

.filename = filename,

.name = umd->u_name,

.qualname = umd->u_qualname ? umd->u_qualname : umd->u_name,

.flags = code_flags,

.code = a->a_bytecode,

.firstlineno = umd->u_firstlineno,

.linetable = a->a_linetable,

.consts = consts,

.names = names,

.localsplusnames = localsplusnames,

.localspluskinds = localspluskinds,

.argcount = posonlyargcount + posorkwargcount,

.posonlyargcount = posonlyargcount,

.kwonlyargcount = kwonlyargcount,

.stacksize = maxdepth,

.exceptiontable = a->a_except_table,

};

if (_PyCode_Validate(&con) < 0) {

goto error;

}

if (_PyCompile_ConstCacheMergeOne(const_cache, &localsplusnames) < 0) {

goto error;

}

con.localsplusnames = localsplusnames;

co = _PyCode_New(&con);

if (co == NULL) {

goto error;

}

error:

Py_XDECREF(names);

Py_XDECREF(consts);

Py_XDECREF(localsplusnames);

Py_XDECREF(localspluskinds);

return co;

}

static int

resolve_jump_offsets(instr_sequence *instrs)

{

/* Compute the size of each instruction and fixup jump args.

* Replace instruction index with position in bytecode.

for (int i = 0; i < instrs->s_used; i++) {

instruction *instr = &instrs->s_instrs[i];

if (OPCODE_HAS_JUMP(instr->i_opcode)) {

instr->i_target = instr->i_oparg;

}

int extended_arg_recompile;

do {

int totsize = 0;

for (int i = 0; i < instrs->s_used; i++) {

instruction *instr = &instrs->s_instrs[i];

instr->i_offset = totsize;

int isize = instr_size(instr);

totsize += isize;

}

extended_arg_recompile = 0;

int offset = 0;

for (int i = 0; i < instrs->s_used; i++) {

instruction *instr = &instrs->s_instrs[i];

int isize = instr_size(instr);

/* jump offsets are computed relative to

* the instruction pointer after fetching

* the jump instruction.

offset += isize;

if (OPCODE_HAS_JUMP(instr->i_opcode)) {

instruction *target = &instrs->s_instrs[instr->i_target];

instr->i_oparg = target->i_offset;

if (instr->i_oparg < offset) {

assert(IS_BACKWARDS_JUMP_OPCODE(instr->i_opcode));

instr->i_oparg = offset - instr->i_oparg;

}

else {

assert(!IS_BACKWARDS_JUMP_OPCODE(instr->i_opcode));

instr->i_oparg = instr->i_oparg - offset;

}

if (instr_size(instr) != isize) {

extended_arg_recompile = 1;

}

/* XXX: This is an awful hack that could hurt performance, but

on the bright side it should work until we come up

with a better solution.

The issue is that in the first loop instr_size() is

called, and it requires i_oparg be set appropriately.

There is a bootstrap problem because i_oparg is

calculated in the second loop above.

So we loop until we stop seeing new EXTENDED_ARGs.

The only EXTENDED_ARGs that could be popping up are

ones in jump instructions. So this should converge

fairly quickly.

} while (extended_arg_recompile);

return SUCCESS;

}

static int

resolve_unconditional_jumps(instr_sequence *instrs)

{

/* Resolve directions of unconditional jumps */

for (int i = 0; i < instrs->s_used; i++) {

instruction *instr = &instrs->s_instrs[i];

bool is_forward = (instr->i_oparg > i);

switch(instr->i_opcode) {

case JUMP:

assert(is_pseudo_target(JUMP, JUMP_FORWARD));

assert(is_pseudo_target(JUMP, JUMP_BACKWARD));

instr->i_opcode = is_forward ? JUMP_FORWARD : JUMP_BACKWARD;

break;

case JUMP_NO_INTERRUPT:

assert(is_pseudo_target(JUMP_NO_INTERRUPT, JUMP_FORWARD));

assert(is_pseudo_target(JUMP_NO_INTERRUPT, JUMP_BACKWARD_NO_INTERRUPT));

instr->i_opcode = is_forward ?

JUMP_FORWARD : JUMP_BACKWARD_NO_INTERRUPT;

break;

default:

if (OPCODE_HAS_JUMP(instr->i_opcode) &&

IS_PSEUDO_INSTR(instr->i_opcode)) {

Py_UNREACHABLE();

}

return SUCCESS;

}

PyCodeObject *

_PyAssemble_MakeCodeObject(_PyCompile_CodeUnitMetadata *umd, PyObject *const_cache,

PyObject *consts, int maxdepth, instr_sequence *instrs,

int nlocalsplus, int code_flags, PyObject *filename)

{

if (_PyInstructionSequence_ApplyLabelMap(instrs) < 0) {

return NULL;

}

if (resolve_unconditional_jumps(instrs) < 0) {

return NULL;

}

if (resolve_jump_offsets(instrs) < 0) {

return NULL;

}

PyCodeObject *co = NULL;

struct assembler a;

int res = assemble_emit(&a, instrs, umd->u_firstlineno, const_cache);

if (res == SUCCESS) {

co = makecode(umd, &a, const_cache, consts, maxdepth, nlocalsplus,

code_flags, filename);

}

assemble_free(&a);

return co;

}

cpython/Python/assemble.c at 362cd2680b45a36c3467b9721ff7fc0ceb338452 · python/cpython · GitHub

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