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gh-114265: move line number propagation before cfg optimization, remove guarantee_lineno_for_exits (#114267)

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Irit Katriel 2024-01-19 14:49:26 +00:00 • committed by GitHub
parent efb81a60f5
commit 7e49f27b41
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4 changed files with 61 additions and 64 deletions
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3
Lib/importlib/_bootstrap_external.py
View file

@ -463,6 +463,7 @@ def _write_atomic(path, data, mode=0o666):
# Python 3.13a1 3564 (Removed oparg from YIELD_VALUE, changed oparg values of RESUME)
# Python 3.13a1 3565 (Oparg of YIELD_VALUE indicates whether it is in a yield-from)
# Python 3.13a1 3566 (Emit JUMP_NO_INTERRUPT instead of JUMP for non-loop no-lineno cases)
# Python 3.13a1 3567 (Reimplement line number propagation by the compiler)
# Python 3.14 will start with 3600
@ -479,7 +480,7 @@ def _write_atomic(path, data, mode=0o666):
# Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
# in PC/launcher.c must also be updated.
MAGIC_NUMBER = (3566).to_bytes(2, 'little') + b'\r\n'
MAGIC_NUMBER = (3567).to_bytes(2, 'little') + b'\r\n'
_RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little') # For import.c

14
Lib/test/test_dis.py
View file

@ -577,14 +577,10 @@ async def _asyncwith(c):
RETURN_CONST 0 (None)
%4d L12: CLEANUP_THROW
-- L13: JUMP_BACKWARD_NO_INTERRUPT 25 (to L5)
%4d L14: CLEANUP_THROW
-- L15: JUMP_BACKWARD_NO_INTERRUPT 9 (to L11)
%4d L16: PUSH_EXC_INFO
L13: JUMP_BACKWARD_NO_INTERRUPT 25 (to L5)
L14: CLEANUP_THROW
L15: JUMP_BACKWARD_NO_INTERRUPT 9 (to L11)
L16: PUSH_EXC_INFO
WITH_EXCEPT_START
GET_AWAITABLE 2
LOAD_CONST 0 (None)
@ -630,8 +626,6 @@ async def _asyncwith(c):
_asyncwith.__code__.co_firstlineno + 1,
_asyncwith.__code__.co_firstlineno + 3,
_asyncwith.__code__.co_firstlineno + 1,
_asyncwith.__code__.co_firstlineno + 1,
_asyncwith.__code__.co_firstlineno + 1,
_asyncwith.__code__.co_firstlineno + 3,
)

1
Misc/NEWS.d/next/Core and Builtins/2024-01-19-13-18-13.gh-issue-114265.7HAi--.rst Normal file
View file

@ -0,0 +1 @@
Compiler propagates line numbers before optimization, leading to more optimization opportunities and removing the need for the ``guarantee_lineno_for_exits`` hack.

99
Python/flowgraph.c
View file

@ -29,6 +29,7 @@ typedef struct _PyCfgInstruction {
int i_opcode;
int i_oparg;
_PyCompilerSrcLocation i_loc;
unsigned i_loc_propagated : 1; /* location was set by propagate_line_numbers */
struct _PyCfgBasicblock *i_target; /* target block (if jump instruction) */
struct _PyCfgBasicblock *i_except; /* target block when exception is raised */
} cfg_instr;
@ -504,6 +505,21 @@ no_redundant_jumps(cfg_builder *g) {
return true;
}
static bool
all_exits_have_lineno(basicblock *entryblock) {
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 (instr->i_opcode == RETURN_VALUE) {
if (instr->i_loc.lineno < 0) {
assert(0);
return false;
}
}
}
}
return true;
}
#endif
/***** CFG preprocessing (jump targets and exceptions) *****/
@ -940,7 +956,10 @@ label_exception_targets(basicblock *entryblock) {
/***** CFG optimizations *****/
static int
mark_reachable(basicblock *entryblock) {
remove_unreachable(basicblock *entryblock) {
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
b->b_predecessors = 0;
}
basicblock **stack = make_cfg_traversal_stack(entryblock);
if (stack == NULL) {
return ERROR;
@ -972,6 +991,14 @@ mark_reachable(basicblock *entryblock) {
}
}
PyMem_Free(stack);
/* Delete unreachable instructions */
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
if (b->b_predecessors == 0) {
b->b_iused = 0;
b->b_except_handler = 0;
}
}
return SUCCESS;
}
@ -1149,13 +1176,15 @@ jump_thread(cfg_instr *inst, cfg_instr *target, int opcode)
assert(is_jump(target));
// bpo-45773: If inst->i_target == target->i_target, then nothing actually
// changes (and we fall into an infinite loop):
if (inst->i_loc.lineno == -1) assert(inst->i_loc_propagated);
if (target->i_loc.lineno == -1) assert(target->i_loc_propagated);
if ((inst->i_loc.lineno == target->i_loc.lineno ||
inst->i_loc.lineno == -1 || target->i_loc.lineno == -1) &&
inst->i_loc_propagated || target->i_loc_propagated) &&
inst->i_target != target->i_target)
{
inst->i_target = target->i_target;
inst->i_opcode = opcode;
if (inst->i_loc.lineno == -1) {
if (inst->i_loc_propagated && !target->i_loc_propagated) {
inst->i_loc = target->i_loc;
}
return true;
@ -1714,6 +1743,7 @@ optimize_basic_block(PyObject *const_cache, basicblock *bb, PyObject *consts)
return ERROR;
}
static int resolve_line_numbers(cfg_builder *g, int firstlineno);
/* Perform optimizations on a control flow graph.
The consts object should still be in list form to allow new constants
@ -1723,41 +1753,31 @@ optimize_basic_block(PyObject *const_cache, basicblock *bb, PyObject *consts)
NOPs. Later those NOPs are removed.
*/
static int
optimize_cfg(cfg_builder *g, PyObject *consts, PyObject *const_cache)
optimize_cfg(cfg_builder *g, PyObject *consts, PyObject *const_cache, int firstlineno)
{
assert(PyDict_CheckExact(const_cache));
RETURN_IF_ERROR(check_cfg(g));
for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
RETURN_IF_ERROR(inline_small_exit_blocks(b));
}
RETURN_IF_ERROR(remove_unreachable(g->g_entryblock));
RETURN_IF_ERROR(resolve_line_numbers(g, firstlineno));
for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
RETURN_IF_ERROR(optimize_basic_block(const_cache, b, consts));
assert(b->b_predecessors == 0);
}
RETURN_IF_ERROR(remove_redundant_nops_and_pairs(g->g_entryblock));
for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
RETURN_IF_ERROR(inline_small_exit_blocks(b));
}
RETURN_IF_ERROR(mark_reachable(g->g_entryblock));
RETURN_IF_ERROR(remove_unreachable(g->g_entryblock));
/* Delete unreachable instructions */
for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
if (b->b_predecessors == 0) {
b->b_iused = 0;
b->b_except_handler = 0;
}
}
for (int n = 0; n < 2; n++) {
for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
remove_redundant_nops(b);
}
RETURN_IF_ERROR(remove_redundant_jumps(g));
for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
remove_redundant_nops(b);
}
RETURN_IF_ERROR(remove_redundant_jumps(g));
assert(no_redundant_jumps(g));
return SUCCESS;
}
@ -2174,7 +2194,13 @@ push_cold_blocks_to_end(cfg_builder *g) {
if (!IS_LABEL(b->b_next->b_label)) {
b->b_next->b_label.id = next_lbl++;
}
basicblock_addop(explicit_jump, JUMP_NO_INTERRUPT, b->b_next->b_label.id, NO_LOCATION);
cfg_instr *prev_instr = basicblock_last_instr(b);
// b cannot be empty because at the end of an exception handler
// there is always a POP_EXCEPT + RERAISE/RETURN
assert(prev_instr);
basicblock_addop(explicit_jump, JUMP_NO_INTERRUPT, b->b_next->b_label.id,
prev_instr->i_loc);
explicit_jump->b_cold = 1;
explicit_jump->b_next = b->b_next;
b->b_next = explicit_jump;
@ -2345,6 +2371,7 @@ propagate_line_numbers(basicblock *entryblock) {
for (int i = 0; i < b->b_iused; i++) {
if (b->b_instr[i].i_loc.lineno < 0) {
b->b_instr[i].i_loc = prev_location;
b->b_instr[i].i_loc_propagated = 1;
}
else {
prev_location = b->b_instr[i].i_loc;
@ -2354,6 +2381,7 @@ propagate_line_numbers(basicblock *entryblock) {
if (b->b_next->b_iused > 0) {
if (b->b_next->b_instr[0].i_loc.lineno < 0) {
b->b_next->b_instr[0].i_loc = prev_location;
b->b_next->b_instr[0].i_loc_propagated = 1;
}
}
}
@ -2362,46 +2390,18 @@ propagate_line_numbers(basicblock *entryblock) {
if (target->b_predecessors == 1) {
if (target->b_instr[0].i_loc.lineno < 0) {
target->b_instr[0].i_loc = prev_location;
target->b_instr[0].i_loc_propagated = 1;
}
}
}
}
}
/* Make sure that all returns have a line number, even if early passes
* have failed to propagate a correct line number.
* The resulting line number may not be correct according to PEP 626,
* but should be "good enough", and no worse than in older versions. */
static void
guarantee_lineno_for_exits(basicblock *entryblock, int firstlineno) {
int lineno = firstlineno;
assert(lineno > 0);
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
cfg_instr *last = basicblock_last_instr(b);
if (last == NULL) {
continue;
}
if (last->i_loc.lineno < 0) {
if (last->i_opcode == RETURN_VALUE) {
for (int i = 0; i < b->b_iused; i++) {
assert(b->b_instr[i].i_loc.lineno < 0);
b->b_instr[i].i_loc.lineno = lineno;
}
}
}
else {
lineno = last->i_loc.lineno;
}
}
}
static int
resolve_line_numbers(cfg_builder *g, int firstlineno)
{
RETURN_IF_ERROR(duplicate_exits_without_lineno(g));
propagate_line_numbers(g->g_entryblock);
guarantee_lineno_for_exits(g->g_entryblock, firstlineno);
return SUCCESS;
}
@ -2417,7 +2417,7 @@ _PyCfg_OptimizeCodeUnit(cfg_builder *g, PyObject *consts, PyObject *const_cache,
RETURN_IF_ERROR(label_exception_targets(g->g_entryblock));
/** Optimization **/
RETURN_IF_ERROR(optimize_cfg(g, consts, const_cache));
RETURN_IF_ERROR(optimize_cfg(g, consts, const_cache, firstlineno));
RETURN_IF_ERROR(remove_unused_consts(g->g_entryblock, consts));
RETURN_IF_ERROR(
add_checks_for_loads_of_uninitialized_variables(
@ -2425,6 +2425,7 @@ _PyCfg_OptimizeCodeUnit(cfg_builder *g, PyObject *consts, PyObject *const_cache,
insert_superinstructions(g);
RETURN_IF_ERROR(push_cold_blocks_to_end(g));
assert(all_exits_have_lineno(g->g_entryblock));
RETURN_IF_ERROR(resolve_line_numbers(g, firstlineno));
return SUCCESS;
}