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#include "Python.h"
#include "opcode.h"
#include "pycore_flowgraph.h"
#include "pycore_compile.h"
#include "pycore_intrinsics.h"
#include "pycore_pymem.h" // _PyMem_IsPtrFreed()
#include "pycore_long.h" // _PY_IS_SMALL_INT()
#include "pycore_opcode_utils.h"
#include "pycore_opcode_metadata.h" // OPCODE_HAS_ARG, etc
#include <stdbool.h>
#undef SUCCESS
#undef ERROR
#define SUCCESS 0
#define ERROR -1
#define RETURN_IF_ERROR(X) \
if ((X) == -1) { \
return ERROR; \
}
#define DEFAULT_BLOCK_SIZE 16
typedef _Py_SourceLocation location;
typedef _PyJumpTargetLabel jump_target_label;
typedef struct _PyCfgInstruction {
int i_opcode;
int i_oparg;
_Py_SourceLocation i_loc;
struct _PyCfgBasicblock *i_target; /* target block (if jump instruction) */
struct _PyCfgBasicblock *i_except; /* target block when exception is raised */
} cfg_instr;
typedef struct _PyCfgBasicblock {
/* Each basicblock in a compilation unit is linked via b_list in the
reverse order that the block are allocated. b_list points to the next
block in this list, not to be confused with b_next, which is next by
control flow. */
struct _PyCfgBasicblock *b_list;
/* The label of this block if it is a jump target, -1 otherwise */
_PyJumpTargetLabel b_label;
/* Exception stack at start of block, used by assembler to create the exception handling table */
struct _PyCfgExceptStack *b_exceptstack;
/* pointer to an array of instructions, initially NULL */
cfg_instr *b_instr;
/* If b_next is non-NULL, it is a pointer to the next
block reached by normal control flow. */
struct _PyCfgBasicblock *b_next;
/* number of instructions used */
int b_iused;
/* length of instruction array (b_instr) */
int b_ialloc;
/* Used by add_checks_for_loads_of_unknown_variables */
uint64_t b_unsafe_locals_mask;
/* Number of predecessors that a block has. */
int b_predecessors;
/* depth of stack upon entry of block, computed by stackdepth() */
int b_startdepth;
/* Basic block is an exception handler that preserves lasti */
unsigned b_preserve_lasti : 1;
/* Used by compiler passes to mark whether they have visited a basic block. */
unsigned b_visited : 1;
/* b_except_handler is used by the cold-detection algorithm to mark exception targets */
unsigned b_except_handler : 1;
/* b_cold is true if this block is not perf critical (like an exception handler) */
unsigned b_cold : 1;
/* b_warm is used by the cold-detection algorithm to mark blocks which are definitely not cold */
unsigned b_warm : 1;
} basicblock;
struct _PyCfgBuilder {
/* The entryblock, at which control flow begins. All blocks of the
CFG are reachable through the b_next links */
struct _PyCfgBasicblock *g_entryblock;
/* Pointer to the most recently allocated block. By following
b_list links, you can reach all allocated blocks. */
struct _PyCfgBasicblock *g_block_list;
/* pointer to the block currently being constructed */
struct _PyCfgBasicblock *g_curblock;
/* label for the next instruction to be placed */
_PyJumpTargetLabel g_current_label;
};
typedef struct _PyCfgBuilder cfg_builder;
#define SAME_LABEL(L1, L2) ((L1).id == (L2).id)
#define IS_LABEL(L) (!SAME_LABEL((L), (NO_LABEL)))
#define LOCATION(LNO, END_LNO, COL, END_COL) \
((const _Py_SourceLocation){(LNO), (END_LNO), (COL), (END_COL)})
static inline int
is_block_push(cfg_instr *i)
{
assert(OPCODE_HAS_ARG(i->i_opcode) || !IS_BLOCK_PUSH_OPCODE(i->i_opcode));
return IS_BLOCK_PUSH_OPCODE(i->i_opcode);
}
static inline int
is_jump(cfg_instr *i)
{
return OPCODE_HAS_JUMP(i->i_opcode);
}
/* One arg*/
#define INSTR_SET_OP1(I, OP, ARG) \
do { \
assert(OPCODE_HAS_ARG(OP)); \
cfg_instr *_instr__ptr_ = (I); \
_instr__ptr_->i_opcode = (OP); \
_instr__ptr_->i_oparg = (ARG); \
} while (0);
/* No args*/
#define INSTR_SET_OP0(I, OP) \
do { \
assert(!OPCODE_HAS_ARG(OP)); \
cfg_instr *_instr__ptr_ = (I); \
_instr__ptr_->i_opcode = (OP); \
_instr__ptr_->i_oparg = 0; \
} while (0);
#define INSTR_SET_LOC(I, LOC) \
do { \
cfg_instr *_instr__ptr_ = (I); \
_instr__ptr_->i_loc = (LOC); \
} while (0);
/***** Blocks *****/
/* Returns the offset of the next instruction in the current block's
b_instr array. Resizes the b_instr as necessary.
Returns -1 on failure.
*/
static int
basicblock_next_instr(basicblock *b)
{
assert(b != NULL);
RETURN_IF_ERROR(
_PyCompile_EnsureArrayLargeEnough(
b->b_iused + 1,
(void**)&b->b_instr,
&b->b_ialloc,
DEFAULT_BLOCK_SIZE,
sizeof(cfg_instr)));
return b->b_iused++;
}
static cfg_instr *
basicblock_last_instr(const basicblock *b) {
assert(b->b_iused >= 0);
if (b->b_iused > 0) {
assert(b->b_instr != NULL);
return &b->b_instr[b->b_iused - 1];
}
return NULL;
}
/* Allocate a new block and return a pointer to it.
Returns NULL on error.
*/
static basicblock *
cfg_builder_new_block(cfg_builder *g)
{
basicblock *b = (basicblock *)PyMem_Calloc(1, sizeof(basicblock));
if (b == NULL) {
PyErr_NoMemory();
return NULL;
}
/* Extend the singly linked list of blocks with new block. */
b->b_list = g->g_block_list;
g->g_block_list = b;
b->b_label = NO_LABEL;
return b;
}
static int
basicblock_addop(basicblock *b, int opcode, int oparg, location loc)
{
assert(IS_WITHIN_OPCODE_RANGE(opcode));
assert(!IS_ASSEMBLER_OPCODE(opcode));
assert(OPCODE_HAS_ARG(opcode) || HAS_TARGET(opcode) || oparg == 0);
assert(0 <= oparg && oparg < (1 << 30));
int off = basicblock_next_instr(b);
if (off < 0) {
return ERROR;
}
cfg_instr *i = &b->b_instr[off];
i->i_opcode = opcode;
i->i_oparg = oparg;
i->i_target = NULL;
i->i_loc = loc;
return SUCCESS;
}
static int
basicblock_add_jump(basicblock *b, int opcode, basicblock *target, location loc)
{
cfg_instr *last = basicblock_last_instr(b);
if (last && is_jump(last)) {
return ERROR;
}
RETURN_IF_ERROR(
basicblock_addop(b, opcode, target->b_label.id, loc));
last = basicblock_last_instr(b);
assert(last && last->i_opcode == opcode);
last->i_target = target;
return SUCCESS;
}
static inline int
basicblock_append_instructions(basicblock *to, basicblock *from)
{
for (int i = 0; i < from->b_iused; i++) {
int n = basicblock_next_instr(to);
if (n < 0) {
return ERROR;
}
to->b_instr[n] = from->b_instr[i];
}
return SUCCESS;
}
static inline int
basicblock_nofallthrough(const basicblock *b) {
cfg_instr *last = basicblock_last_instr(b);
return (last &&
(IS_SCOPE_EXIT_OPCODE(last->i_opcode) ||
IS_UNCONDITIONAL_JUMP_OPCODE(last->i_opcode)));
}
#define BB_NO_FALLTHROUGH(B) (basicblock_nofallthrough(B))
#define BB_HAS_FALLTHROUGH(B) (!basicblock_nofallthrough(B))
static basicblock *
copy_basicblock(cfg_builder *g, basicblock *block)
{
/* Cannot copy a block if it has a fallthrough, since
* a block can only have one fallthrough predecessor.
*/
assert(BB_NO_FALLTHROUGH(block));
basicblock *result = cfg_builder_new_block(g);
if (result == NULL) {
return NULL;
}
if (basicblock_append_instructions(result, block) < 0) {
return NULL;
}
return result;
}
static int
basicblock_insert_instruction(basicblock *block, int pos, cfg_instr *instr) {
RETURN_IF_ERROR(basicblock_next_instr(block));
for (int i = block->b_iused - 1; i > pos; i--) {
block->b_instr[i] = block->b_instr[i-1];
}
block->b_instr[pos] = *instr;
return SUCCESS;
}
/* For debugging purposes only */
#if 0
static void
dump_instr(cfg_instr *i)
{
const char *jump = is_jump(i) ? "jump " : "";
char arg[128];
*arg = '\0';
if (OPCODE_HAS_ARG(i->i_opcode)) {
sprintf(arg, "arg: %d ", i->i_oparg);
}
if (HAS_TARGET(i->i_opcode)) {
sprintf(arg, "target: %p [%d] ", i->i_target, i->i_oparg);
}
fprintf(stderr, "line: %d, %s (%d) %s%s\n",
i->i_loc.lineno, _PyOpcode_OpName[i->i_opcode], i->i_opcode, arg, jump);
}
static inline int
basicblock_returns(const basicblock *b) {
cfg_instr *last = basicblock_last_instr(b);
return last && last->i_opcode == RETURN_VALUE;
}
static void
dump_basicblock(const basicblock *b)
{
const char *b_return = basicblock_returns(b) ? "return " : "";
fprintf(stderr, "%d: [EH=%d CLD=%d WRM=%d NO_FT=%d %p] used: %d, depth: %d, preds: %d %s\n",
b->b_label.id, b->b_except_handler, b->b_cold, b->b_warm, BB_NO_FALLTHROUGH(b), b, b->b_iused,
b->b_startdepth, b->b_predecessors, b_return);
if (b->b_instr) {
int i;
for (i = 0; i < b->b_iused; i++) {
fprintf(stderr, " [%02d] ", i);
dump_instr(b->b_instr + i);
}
}
}
void
_PyCfgBuilder_DumpGraph(const basicblock *entryblock)
{
for (const basicblock *b = entryblock; b != NULL; b = b->b_next) {
dump_basicblock(b);
}
}
#endif
/***** CFG construction and modification *****/
static basicblock *
cfg_builder_use_next_block(cfg_builder *g, basicblock *block)
{
assert(block != NULL);
g->g_curblock->b_next = block;
g->g_curblock = block;
return block;
}
static inline int
basicblock_exits_scope(const basicblock *b) {
cfg_instr *last = basicblock_last_instr(b);
return last && IS_SCOPE_EXIT_OPCODE(last->i_opcode);
}
static inline int
basicblock_has_eval_break(const basicblock *b) {
for (int i = 0; i < b->b_iused; i++) {
if (OPCODE_HAS_EVAL_BREAK(b->b_instr[i].i_opcode)) {
return true;
}
}
return false;
}
static bool
cfg_builder_current_block_is_terminated(cfg_builder *g)
{
cfg_instr *last = basicblock_last_instr(g->g_curblock);
if (last && IS_TERMINATOR_OPCODE(last->i_opcode)) {
return true;
}
if (IS_LABEL(g->g_current_label)) {
if (last || IS_LABEL(g->g_curblock->b_label)) {
return true;
}
else {
/* current block is empty, label it */
g->g_curblock->b_label = g->g_current_label;
g->g_current_label = NO_LABEL;
}
}
return false;
}
static int
cfg_builder_maybe_start_new_block(cfg_builder *g)
{
if (cfg_builder_current_block_is_terminated(g)) {
basicblock *b = cfg_builder_new_block(g);
if (b == NULL) {
return ERROR;
}
b->b_label = g->g_current_label;
g->g_current_label = NO_LABEL;
cfg_builder_use_next_block(g, b);
}
return SUCCESS;
}
#ifndef NDEBUG
static bool
cfg_builder_check(cfg_builder *g)
{
assert(g->g_entryblock->b_iused > 0);
for (basicblock *block = g->g_block_list; block != NULL; block = block->b_list) {
assert(!_PyMem_IsPtrFreed(block));
if (block->b_instr != NULL) {
assert(block->b_ialloc > 0);
assert(block->b_iused >= 0);
assert(block->b_ialloc >= block->b_iused);
}
else {
assert (block->b_iused == 0);
assert (block->b_ialloc == 0);
}
}
return true;
}
#endif
static int
init_cfg_builder(cfg_builder *g)
{
g->g_block_list = NULL;
basicblock *block = cfg_builder_new_block(g);
if (block == NULL) {
return ERROR;
}
g->g_curblock = g->g_entryblock = block;
g->g_current_label = NO_LABEL;
return SUCCESS;
}
cfg_builder *
_PyCfgBuilder_New(void)
{
cfg_builder *g = PyMem_Malloc(sizeof(cfg_builder));
if (g == NULL) {
PyErr_NoMemory();
return NULL;
}
memset(g, 0, sizeof(cfg_builder));
if (init_cfg_builder(g) < 0) {
PyMem_Free(g);
return NULL;
}
return g;
}
void
_PyCfgBuilder_Free(cfg_builder *g)
{
if (g == NULL) {
return;
}
assert(cfg_builder_check(g));
basicblock *b = g->g_block_list;
while (b != NULL) {
if (b->b_instr) {
PyMem_Free((void *)b->b_instr);
}
basicblock *next = b->b_list;
PyMem_Free((void *)b);
b = next;
}
PyMem_Free(g);
}
int
_PyCfgBuilder_CheckSize(cfg_builder *g)
{
int nblocks = 0;
for (basicblock *b = g->g_block_list; b != NULL; b = b->b_list) {
nblocks++;
}
if ((size_t)nblocks > SIZE_MAX / sizeof(basicblock *)) {
PyErr_NoMemory();
return ERROR;
}
return SUCCESS;
}
int
_PyCfgBuilder_UseLabel(cfg_builder *g, jump_target_label lbl)
{
g->g_current_label = lbl;
return cfg_builder_maybe_start_new_block(g);
}
int
_PyCfgBuilder_Addop(cfg_builder *g, int opcode, int oparg, location loc)
{
RETURN_IF_ERROR(cfg_builder_maybe_start_new_block(g));
return basicblock_addop(g->g_curblock, opcode, oparg, loc);
}
static basicblock *
next_nonempty_block(basicblock *b)
{
while (b && b->b_iused == 0) {
b = b->b_next;
}
return b;
}
/***** debugging helpers *****/
#ifndef NDEBUG
static int remove_redundant_nops(cfg_builder *g);
static bool
no_redundant_nops(cfg_builder *g) {
if (remove_redundant_nops(g) != 0) {
return false;
}
return true;
}
static bool
no_redundant_jumps(cfg_builder *g) {
for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
cfg_instr *last = basicblock_last_instr(b);
if (last != NULL) {
if (IS_UNCONDITIONAL_JUMP_OPCODE(last->i_opcode)) {
basicblock *next = next_nonempty_block(b->b_next);
basicblock *jump_target = next_nonempty_block(last->i_target);
if (jump_target == next) {
assert(next);
if (last->i_loc.lineno == next->b_instr[0].i_loc.lineno) {
assert(0);
return false;
}
}
}
}
}
return true;
}
#endif
/***** CFG preprocessing (jump targets and exceptions) *****/
static int
normalize_jumps_in_block(cfg_builder *g, basicblock *b) {
cfg_instr *last = basicblock_last_instr(b);
if (last == NULL || !IS_CONDITIONAL_JUMP_OPCODE(last->i_opcode)) {
return SUCCESS;
}
assert(!IS_ASSEMBLER_OPCODE(last->i_opcode));
bool is_forward = last->i_target->b_visited == 0;
if (is_forward) {
RETURN_IF_ERROR(
basicblock_addop(b, NOT_TAKEN, 0, last->i_loc));
return SUCCESS;
}
int reversed_opcode = 0;
switch(last->i_opcode) {
case POP_JUMP_IF_NOT_NONE:
reversed_opcode = POP_JUMP_IF_NONE;
break;
case POP_JUMP_IF_NONE:
reversed_opcode = POP_JUMP_IF_NOT_NONE;
break;
case POP_JUMP_IF_FALSE:
reversed_opcode = POP_JUMP_IF_TRUE;
break;
case POP_JUMP_IF_TRUE:
reversed_opcode = POP_JUMP_IF_FALSE;
break;
}
/* transform 'conditional jump T' to
* 'reversed_jump b_next' followed by 'jump_backwards T'
*/
basicblock *target = last->i_target;
basicblock *backwards_jump = cfg_builder_new_block(g);
if (backwards_jump == NULL) {
return ERROR;
}
RETURN_IF_ERROR(
basicblock_addop(backwards_jump, NOT_TAKEN, 0, last->i_loc));
RETURN_IF_ERROR(
basicblock_add_jump(backwards_jump, JUMP, target, last->i_loc));
last->i_opcode = reversed_opcode;
last->i_target = b->b_next;
backwards_jump->b_cold = b->b_cold;
backwards_jump->b_next = b->b_next;
b->b_next = backwards_jump;
return SUCCESS;
}
static int
normalize_jumps(cfg_builder *g)
{
basicblock *entryblock = g->g_entryblock;
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
b->b_visited = 0;
}
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
b->b_visited = 1;
RETURN_IF_ERROR(normalize_jumps_in_block(g, b));
}
return SUCCESS;
}
static int
check_cfg(cfg_builder *g) {
for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
/* Raise SystemError if jump or exit is not last instruction in the block. */
for (int i = 0; i < b->b_iused; i++) {
int opcode = b->b_instr[i].i_opcode;
assert(!IS_ASSEMBLER_OPCODE(opcode));
if (IS_TERMINATOR_OPCODE(opcode)) {
if (i != b->b_iused - 1) {
PyErr_SetString(PyExc_SystemError, "malformed control flow graph.");
return ERROR;
}
}
}
}
return SUCCESS;
}
static int
get_max_label(basicblock *entryblock)
{
int lbl = -1;
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
if (b->b_label.id > lbl) {
lbl = b->b_label.id;
}
}
return lbl;
}
/* Calculate the actual jump target from the target_label */
static int
translate_jump_labels_to_targets(basicblock *entryblock)
{
int max_label = get_max_label(entryblock);
size_t mapsize = sizeof(basicblock *) * (max_label + 1);
basicblock **label2block = (basicblock **)PyMem_Malloc(mapsize);
if (!label2block) {
PyErr_NoMemory();
return ERROR;
}
memset(label2block, 0, mapsize);
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
if (b->b_label.id >= 0) {
label2block[b->b_label.id] = b;
}
}
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
for (int i = 0; i < b->b_iused; i++) {
cfg_instr *instr = &b->b_instr[i];
assert(instr->i_target == NULL);
if (HAS_TARGET(instr->i_opcode)) {
int lbl = instr->i_oparg;
assert(lbl >= 0 && lbl <= max_label);
instr->i_target = label2block[lbl];
assert(instr->i_target != NULL);
assert(instr->i_target->b_label.id == lbl);
}
}
}
PyMem_Free(label2block);
return SUCCESS;
}
static int
mark_except_handlers(basicblock *entryblock) {
#ifndef NDEBUG
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
assert(!b->b_except_handler);
}
#endif
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
for (int i=0; i < b->b_iused; i++) {
cfg_instr *instr = &b->b_instr[i];
if (is_block_push(instr)) {
instr->i_target->b_except_handler = 1;
}
}
}
return SUCCESS;
}
struct _PyCfgExceptStack {
basicblock *handlers[CO_MAXBLOCKS+2];
int depth;
};
static basicblock *
push_except_block(struct _PyCfgExceptStack *stack, cfg_instr *setup) {
assert(is_block_push(setup));
int opcode = setup->i_opcode;
basicblock * target = setup->i_target;
if (opcode == SETUP_WITH || opcode == SETUP_CLEANUP) {
target->b_preserve_lasti = 1;
}
assert(stack->depth <= CO_MAXBLOCKS);
stack->handlers[++stack->depth] = target;
return target;
}
static basicblock *
pop_except_block(struct _PyCfgExceptStack *stack) {
assert(stack->depth > 0);
return stack->handlers[--stack->depth];
}
static basicblock *
except_stack_top(struct _PyCfgExceptStack *stack) {
return stack->handlers[stack->depth];
}
static struct _PyCfgExceptStack *
make_except_stack(void) {
struct _PyCfgExceptStack *new = PyMem_Malloc(sizeof(struct _PyCfgExceptStack));
if (new == NULL) {
PyErr_NoMemory();
return NULL;
}
new->depth = 0;
new->handlers[0] = NULL;
return new;
}
static struct _PyCfgExceptStack *
copy_except_stack(struct _PyCfgExceptStack *stack) {
struct _PyCfgExceptStack *copy = PyMem_Malloc(sizeof(struct _PyCfgExceptStack));
if (copy == NULL) {
PyErr_NoMemory();
return NULL;
}
memcpy(copy, stack, sizeof(struct _PyCfgExceptStack));
return copy;
}
static basicblock**
make_cfg_traversal_stack(basicblock *entryblock) {
int nblocks = 0;
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
b->b_visited = 0;
nblocks++;
}
basicblock **stack = (basicblock **)PyMem_Malloc(sizeof(basicblock *) * nblocks);
if (!stack) {
PyErr_NoMemory();
}
return stack;
}
/* Compute the stack effects of opcode with argument oparg.
Some opcodes have different stack effect when jump to the target and
when not jump. The 'jump' parameter specifies the case:
* 0 -- when not jump
* 1 -- when jump
* -1 -- maximal
*/
typedef struct {
/* The stack effect of the instruction. */
int net;
/* The maximum stack usage of the instruction. Some instructions may
* temporarily push extra values to the stack while they are executing.
*/
int max;
} stack_effects;
Py_LOCAL(int)
get_stack_effects(int opcode, int oparg, int jump, stack_effects *effects)
{
if (opcode < 0) {
return -1;
}
if ((opcode <= MAX_REAL_OPCODE) && (_PyOpcode_Deopt[opcode] != opcode)) {
// Specialized instructions are not supported.
return -1;
}
int popped = _PyOpcode_num_popped(opcode, oparg);
int pushed = _PyOpcode_num_pushed(opcode, oparg);
if (popped < 0 || pushed < 0) {
return -1;
}
if (IS_BLOCK_PUSH_OPCODE(opcode) && !jump) {
effects->net = 0;
effects->max = 0;
return 0;
}
if (_PyOpcode_max_stack_effect(opcode, oparg, &effects->max) < 0) {
return -1;
}
effects->net = pushed - popped;
assert(effects->max >= effects->net);
return 0;
}
Py_LOCAL_INLINE(int)
stackdepth_push(basicblock ***sp, basicblock *b, int depth)
{
if (!(b->b_startdepth < 0 || b->b_startdepth == depth)) {
PyErr_Format(PyExc_ValueError, "Invalid CFG, inconsistent stackdepth");
return ERROR;
}
if (b->b_startdepth < depth && b->b_startdepth < 100) {
assert(b->b_startdepth < 0);
b->b_startdepth = depth;
*(*sp)++ = b;
}
return SUCCESS;
}
/* Find the flow path that needs the largest stack. We assume that
* cycles in the flow graph have no net effect on the stack depth.
*/
static int
calculate_stackdepth(cfg_builder *g)
{
basicblock *entryblock = g->g_entryblock;
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
b->b_startdepth = INT_MIN;
}
basicblock **stack = make_cfg_traversal_stack(entryblock);
if (!stack) {
return ERROR;
}
int stackdepth = -1;
int maxdepth = 0;
basicblock **sp = stack;
if (stackdepth_push(&sp, entryblock, 0) < 0) {
goto error;
}
while (sp != stack) {
basicblock *b = *--sp;
int depth = b->b_startdepth;
assert(depth >= 0);
basicblock *next = b->b_next;
for (int i = 0; i < b->b_iused; i++) {
cfg_instr *instr = &b->b_instr[i];
stack_effects effects;
if (get_stack_effects(instr->i_opcode, instr->i_oparg, 0, &effects) < 0) {
PyErr_Format(PyExc_SystemError,
"Invalid stack effect for opcode=%d, arg=%i",
instr->i_opcode, instr->i_oparg);
goto error;
}
int new_depth = depth + effects.net;
if (new_depth < 0) {
PyErr_Format(PyExc_ValueError,
"Invalid CFG, stack underflow");
goto error;
}
maxdepth = Py_MAX(maxdepth, depth + effects.max);
if (HAS_TARGET(instr->i_opcode) && instr->i_opcode != END_ASYNC_FOR) {
if (get_stack_effects(instr->i_opcode, instr->i_oparg, 1, &effects) < 0) {
PyErr_Format(PyExc_SystemError,
"Invalid stack effect for opcode=%d, arg=%i",
instr->i_opcode, instr->i_oparg);
goto error;
}
int target_depth = depth + effects.net;
assert(target_depth >= 0); /* invalid code or bug in stackdepth() */
maxdepth = Py_MAX(maxdepth, depth + effects.max);
if (stackdepth_push(&sp, instr->i_target, target_depth) < 0) {
goto error;
}
}
depth = new_depth;
assert(!IS_ASSEMBLER_OPCODE(instr->i_opcode));
if (IS_UNCONDITIONAL_JUMP_OPCODE(instr->i_opcode) ||
IS_SCOPE_EXIT_OPCODE(instr->i_opcode))
{
/* remaining code is dead */
next = NULL;
break;
}
}
if (next != NULL) {
assert(BB_HAS_FALLTHROUGH(b));
if (stackdepth_push(&sp, next, depth) < 0) {
goto error;
}
}
}
stackdepth = maxdepth;
error:
PyMem_Free(stack);
return stackdepth;
}
static int
label_exception_targets(basicblock *entryblock) {
basicblock **todo_stack = make_cfg_traversal_stack(entryblock);
if (todo_stack == NULL) {
return ERROR;
}
struct _PyCfgExceptStack *except_stack = make_except_stack();
if (except_stack == NULL) {
PyMem_Free(todo_stack);
PyErr_NoMemory();
return ERROR;
}
except_stack->depth = 0;
todo_stack[0] = entryblock;
entryblock->b_visited = 1;
entryblock->b_exceptstack = except_stack;
basicblock **todo = &todo_stack[1];
basicblock *handler = NULL;
while (todo > todo_stack) {
todo--;
basicblock *b = todo[0];
assert(b->b_visited == 1);
except_stack = b->b_exceptstack;
assert(except_stack != NULL);
b->b_exceptstack = NULL;
handler = except_stack_top(except_stack);
int last_yield_except_depth = -1;
for (int i = 0; i < b->b_iused; i++) {
cfg_instr *instr = &b->b_instr[i];
if (is_block_push(instr)) {
if (!instr->i_target->b_visited) {
struct _PyCfgExceptStack *copy = copy_except_stack(except_stack);
if (copy == NULL) {
goto error;
}
instr->i_target->b_exceptstack = copy;
todo[0] = instr->i_target;
instr->i_target->b_visited = 1;
todo++;
}
handler = push_except_block(except_stack, instr);
}
else if (instr->i_opcode == POP_BLOCK) {
handler = pop_except_block(except_stack);
INSTR_SET_OP0(instr, NOP);
}
else if (is_jump(instr)) {
instr->i_except = handler;
assert(i == b->b_iused -1);
if (!instr->i_target->b_visited) {
if (BB_HAS_FALLTHROUGH(b)) {
struct _PyCfgExceptStack *copy = copy_except_stack(except_stack);
if (copy == NULL) {
goto error;
}
instr->i_target->b_exceptstack = copy;
}
else {
instr->i_target->b_exceptstack = except_stack;
except_stack = NULL;
}
todo[0] = instr->i_target;
instr->i_target->b_visited = 1;
todo++;
}
}
else if (instr->i_opcode == YIELD_VALUE) {
instr->i_except = handler;
last_yield_except_depth = except_stack->depth;
}
else if (instr->i_opcode == RESUME) {
instr->i_except = handler;
if (instr->i_oparg != RESUME_AT_FUNC_START) {
assert(last_yield_except_depth >= 0);
if (last_yield_except_depth == 1) {
instr->i_oparg |= RESUME_OPARG_DEPTH1_MASK;
}
last_yield_except_depth = -1;
}
}
else {
instr->i_except = handler;
}
}
if (BB_HAS_FALLTHROUGH(b) && !b->b_next->b_visited) {
assert(except_stack != NULL);
b->b_next->b_exceptstack = except_stack;
todo[0] = b->b_next;
b->b_next->b_visited = 1;
todo++;
}
else if (except_stack != NULL) {
PyMem_Free(except_stack);
}
}
#ifdef Py_DEBUG
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
assert(b->b_exceptstack == NULL);
}
#endif
PyMem_Free(todo_stack);
return SUCCESS;
error:
PyMem_Free(todo_stack);
PyMem_Free(except_stack);
return ERROR;
}
/***** CFG optimizations *****/
static int
remove_unreachable(basicblock *entryblock) {
You can’t perform that action at this time.