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gh-114265: remove i_loc_propagated, jump threading does not consider line numbers anymore #114535

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Merged
merged 1 commit into from
Jan 25, 2024
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gh-114265: remove i_loc_propagated, jump threading does not consider line numbers anymore #114535

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3 changes: 2 additions & 1 deletion Lib/test/test_peepholer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1150,10 +1150,11 @@ def get_insts(lno1, lno2, op1, op2):
lno1, lno2 = (4, 5)
with self.subTest(lno = (lno1, lno2), ops = (op1, op2)):
insts = get_insts(lno1, lno2, op1, op2)
op = 'JUMP' if 'JUMP' in (op1, op2) else 'JUMP_NO_INTERRUPT'
expected_insts = [
('LOAD_NAME', 0, 10),
('NOP', 0, 4),
(op2, 0, 5),
(op, 0, 5),
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The expected output was wrong here (and there was a bug) - in the case of 'JUMP' --> 'JUMP_NO_INTERRUPT' we were previously ending up with 'JUMP_NO_INTERRUPT', but we want it to be 'JUMP'.

]
self.cfg_optimization_test(insts, expected_insts, consts=list(range(5)))

Expand Down
88 changes: 47 additions & 41 deletions Python/flowgraph.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,6 @@ 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;
Expand Down Expand Up @@ -146,6 +145,16 @@ basicblock_next_instr(basicblock *b)
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.
*/
Expand Down Expand Up @@ -186,6 +195,22 @@ basicblock_addop(basicblock *b, int opcode, int oparg, location 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 *target, basicblock *source)
{
Expand All @@ -199,16 +224,6 @@ basicblock_append_instructions(basicblock *target, basicblock *source)
return SUCCESS;
}

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;
}

static inline int
basicblock_nofallthrough(const basicblock *b) {
cfg_instr *last = basicblock_last_instr(b);
Expand Down Expand Up @@ -560,8 +575,8 @@ normalize_jumps_in_block(cfg_builder *g, basicblock *b) {
if (backwards_jump == NULL) {
return ERROR;
}
basicblock_addop(backwards_jump, JUMP, target->b_label.id, last->i_loc);
backwards_jump->b_instr[0].i_target = target;
RETURN_IF_ERROR(
basicblock_add_jump(backwards_jump, JUMP, target, last->i_loc));
last->i_opcode = reversed_opcode;
last->i_target = b->b_next;

Expand Down Expand Up @@ -1141,13 +1156,7 @@ remove_redundant_jumps(cfg_builder *g) {
basicblock *next = next_nonempty_block(b->b_next);
if (jump_target == next) {
changes++;
if (last->i_loc_propagated) {
b->b_iused--;
}
else {
assert(last->i_loc.lineno != -1);
INSTR_SET_OP0(last, NOP);
}
INSTR_SET_OP0(last, NOP);
}
}
}
Expand Down Expand Up @@ -1184,23 +1193,23 @@ inline_small_exit_blocks(basicblock *bb) {
// target->i_target using the provided opcode. Return whether or not the
// optimization was successful.
static bool
jump_thread(cfg_instr *inst, cfg_instr *target, int opcode)
jump_thread(basicblock *bb, cfg_instr *inst, cfg_instr *target, int opcode)
{
assert(is_jump(inst));
assert(is_jump(target));
assert(inst == basicblock_last_instr(bb));
// 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_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_propagated && !target->i_loc_propagated) {
inst->i_loc = target->i_loc;
}
if (inst->i_target != target->i_target) {
/* Change inst to NOP and append a jump to target->i_target. The
* NOP will be removed later if it's not needed for the lineno.
*/
INSTR_SET_OP0(inst, NOP);

RETURN_IF_ERROR(
basicblock_add_jump(
bb, opcode, target->i_target, target->i_loc));

return true;
}
return false;
Expand Down Expand Up @@ -1673,29 +1682,29 @@ optimize_basic_block(PyObject *const_cache, basicblock *bb, PyObject *consts)
case POP_JUMP_IF_NONE:
switch (target->i_opcode) {
case JUMP:
i -= jump_thread(inst, target, inst->i_opcode);
i -= jump_thread(bb, inst, target, inst->i_opcode);
}
break;
case POP_JUMP_IF_FALSE:
switch (target->i_opcode) {
case JUMP:
i -= jump_thread(inst, target, POP_JUMP_IF_FALSE);
i -= jump_thread(bb, inst, target, POP_JUMP_IF_FALSE);
}
break;
case POP_JUMP_IF_TRUE:
switch (target->i_opcode) {
case JUMP:
i -= jump_thread(inst, target, POP_JUMP_IF_TRUE);
i -= jump_thread(bb, inst, target, POP_JUMP_IF_TRUE);
}
break;
case JUMP:
case JUMP_NO_INTERRUPT:
switch (target->i_opcode) {
case JUMP:
i -= jump_thread(inst, target, JUMP);
i -= jump_thread(bb, inst, target, JUMP);
continue;
case JUMP_NO_INTERRUPT:
i -= jump_thread(inst, target, opcode);
i -= jump_thread(bb, inst, target, opcode);
continue;
}
break;
Expand All @@ -1707,7 +1716,7 @@ optimize_basic_block(PyObject *const_cache, basicblock *bb, PyObject *consts)
* of FOR_ITER.
*/
/*
i -= jump_thread(inst, target, FOR_ITER);
i -= jump_thread(bb, inst, target, FOR_ITER);
*/
}
break;
Expand Down Expand Up @@ -2410,7 +2419,6 @@ 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;
Expand All @@ -2420,7 +2428,6 @@ 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;
}
}
}
Expand All @@ -2429,7 +2436,6 @@ 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;
}
}
}
Expand Down