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bpo-44626: Merge basic blocks earlier to enable better handling of ex…
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…it blocks without line numbers (GH-27138) (GH-27182)

(cherry picked from commit a86f7da)
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@markshannon
markshannon authored Jul 16, 2021
1 parent 0e349ea commit 37686f7
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Showing 5 changed files with 3,893 additions and 3,827 deletions.
24 changes: 19 additions & 5 deletions Lib/test/test_dis.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1069,7 +1069,7 @@ def jumpy():
Instruction(opname='JUMP_FORWARD', opcode=110, arg=12, argval=144, argrepr='to 144', offset=118, starts_line=None, is_jump_target=False),
Instruction(opname='DUP_TOP', opcode=4, arg=None, argval=None, argrepr='', offset=120, starts_line=22, is_jump_target=True),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=2, argval='ZeroDivisionError', argrepr='ZeroDivisionError', offset=122, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_IF_NOT_EXC_MATCH', opcode=121, arg=106, argval=212, argrepr='to 212', offset=124, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_IF_NOT_EXC_MATCH', opcode=121, arg=120, argval=240, argrepr='to 240', offset=124, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=126, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=128, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=130, starts_line=None, is_jump_target=False),
Expand All @@ -1078,7 +1078,7 @@ def jumpy():
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=136, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=138, starts_line=None, is_jump_target=False),
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=140, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_FORWARD', opcode=110, arg=22, argval=188, argrepr='to 188', offset=142, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_FORWARD', opcode=110, arg=41, argval=226, argrepr='to 226', offset=142, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_FAST', opcode=124, arg=0, argval='i', argrepr='i', offset=144, starts_line=25, is_jump_target=True),
Instruction(opname='SETUP_WITH', opcode=143, arg=12, argval=172, argrepr='to 172', offset=146, starts_line=None, is_jump_target=False),
Instruction(opname='STORE_FAST', opcode=125, arg=1, argval='dodgy', argrepr='dodgy', offset=148, starts_line=None, is_jump_target=False),
Expand All @@ -1092,7 +1092,7 @@ def jumpy():
Instruction(opname='DUP_TOP', opcode=4, arg=None, argval=None, argrepr='', offset=164, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=3, argval=3, argrepr='', offset=166, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=168, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_FORWARD', opcode=110, arg=8, argval=188, argrepr='to 188', offset=170, starts_line=None, is_jump_target=False),
Instruction(opname='JUMP_FORWARD', opcode=110, arg=20, argval=212, argrepr='to 212', offset=170, starts_line=None, is_jump_target=False),
Instruction(opname='WITH_EXCEPT_START', opcode=49, arg=None, argval=None, argrepr='', offset=172, starts_line=None, is_jump_target=True),
Instruction(opname='POP_JUMP_IF_TRUE', opcode=115, arg=89, argval=178, argrepr='to 178', offset=174, starts_line=None, is_jump_target=False),
Instruction(opname='RERAISE', opcode=119, arg=1, argval=1, argrepr='', offset=176, starts_line=None, is_jump_target=False),
Expand All @@ -1101,7 +1101,7 @@ def jumpy():
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=182, starts_line=None, is_jump_target=False),
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=184, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=186, starts_line=None, is_jump_target=False),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=188, starts_line=None, is_jump_target=True),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=188, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=190, starts_line=28, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=10, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=192, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=194, starts_line=None, is_jump_target=False),
Expand All @@ -1113,7 +1113,21 @@ def jumpy():
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=206, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=208, starts_line=None, is_jump_target=False),
Instruction(opname='RERAISE', opcode=119, arg=0, argval=0, argrepr='', offset=210, starts_line=None, is_jump_target=False),
Instruction(opname='RERAISE', opcode=119, arg=0, argval=0, argrepr='', offset=212, starts_line=22, is_jump_target=True),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=212, starts_line=25, is_jump_target=True),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=214, starts_line=28, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=10, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=216, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=218, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=220, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=0, argval=None, argrepr='None', offset=222, starts_line=None, is_jump_target=False),
Instruction(opname='RETURN_VALUE', opcode=83, arg=None, argval=None, argrepr='', offset=224, starts_line=None, is_jump_target=False),
Instruction(opname='POP_BLOCK', opcode=87, arg=None, argval=None, argrepr='', offset=226, starts_line=23, is_jump_target=True),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=228, starts_line=28, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=10, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=230, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=232, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=234, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=0, argval=None, argrepr='None', offset=236, starts_line=None, is_jump_target=False),
Instruction(opname='RETURN_VALUE', opcode=83, arg=None, argval=None, argrepr='', offset=238, starts_line=None, is_jump_target=False),
Instruction(opname='RERAISE', opcode=119, arg=0, argval=0, argrepr='', offset=240, starts_line=22, is_jump_target=True),
]

# One last piece of inspect fodder to check the default line number handling
Expand Down
21 changes: 18 additions & 3 deletions Lib/test/test_sys_settrace.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -986,14 +986,29 @@ def func():
except Exception:
pass

# This doesn't conform to PEP 626
self.run_and_compare(func,
[(0, 'call'),
(1, 'line'),
(2, 'line'),
(3, 'line'),
(5, 'line'),
(5, 'return')])
(3, 'return')])

def test_if_in_if_in_if(self):
def func(a=0, p=1, z=1):
if p:
if a:
if z:
pass
else:
pass
else:
pass

self.run_and_compare(func,
[(0, 'call'),
(1, 'line'),
(2, 'line'),
(2, 'return')])

def test_early_exit_with(self):

Expand Down
64 changes: 48 additions & 16 deletions Python/compile.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6934,10 +6934,11 @@ makecode(struct compiler *c, struct assembler *a, PyObject *consts)
/* For debugging purposes only */
#if 0
static void
dump_instr(const struct instr *i)
dump_instr(struct instr *i)
{
const char *jrel = (is_relative_jump(instr)) ? "jrel " : "";
const char *jabs = (is_jump(instr) && !is_relative_jump(instr))? "jabs " : "";
const char *jrel = (is_relative_jump(i)) ? "jrel " : "";
const char *jabs = (is_jump(i) && !is_relative_jump(i))? "jabs " : "";

char arg[128];

*arg = '\0';
Expand Down Expand Up @@ -6974,6 +6975,9 @@ optimize_cfg(struct compiler *c, struct assembler *a, PyObject *consts);
static int
ensure_exits_have_lineno(struct compiler *c);

static int
extend_block(basicblock *bb);

static int
insert_generator_prefix(struct compiler *c, basicblock *entryblock) {

Expand Down Expand Up @@ -7063,6 +7067,12 @@ assemble(struct compiler *c, int addNone)
}
}

for (basicblock *b = c->u->u_blocks; b != NULL; b = b->b_list) {
if (extend_block(b)) {
return NULL;
}
}

if (ensure_exits_have_lineno(c)) {
return NULL;
}
Expand Down Expand Up @@ -7096,6 +7106,7 @@ assemble(struct compiler *c, int addNone)
if (consts == NULL) {
goto error;
}

if (optimize_cfg(c, &a, consts)) {
goto error;
}
Expand Down Expand Up @@ -7459,19 +7470,14 @@ optimize_basic_block(struct compiler *c, basicblock *bb, PyObject *consts)
goto error;
}
break;
default:
if (inst->i_target->b_exit && inst->i_target->b_iused <= MAX_COPY_SIZE) {
basicblock *to_copy = inst->i_target;
inst->i_opcode = NOP;
for (i = 0; i < to_copy->b_iused; i++) {
int index = compiler_next_instr(bb);
if (index < 0) {
return -1;
}
bb->b_instr[index] = to_copy->b_instr[i];
}
bb->b_exit = 1;
}
}
break;
case FOR_ITER:
assert (i == bb->b_iused-1);
if (target->i_opcode == JUMP_FORWARD) {
if (eliminate_jump_to_jump(bb, inst->i_opcode)) {
goto error;
}
}
break;
case ROT_N:
Expand Down Expand Up @@ -7501,6 +7507,32 @@ optimize_basic_block(struct compiler *c, basicblock *bb, PyObject *consts)
return -1;
}

/* If this block ends with an unconditional jump to an exit block,
* then remove the jump and extend this block with the target.
*/
static int
extend_block(basicblock *bb) {
if (bb->b_iused == 0) {
return 0;
}
struct instr *last = &bb->b_instr[bb->b_iused-1];
if (last->i_opcode != JUMP_ABSOLUTE && last->i_opcode != JUMP_FORWARD) {
return 0;
}
if (last->i_target->b_exit && last->i_target->b_iused <= MAX_COPY_SIZE) {
basicblock *to_copy = last->i_target;
last->i_opcode = NOP;
for (int i = 0; i < to_copy->b_iused; i++) {
int index = compiler_next_instr(bb);
if (index < 0) {
return -1;
}
bb->b_instr[index] = to_copy->b_instr[i];
}
bb->b_exit = 1;
}
return 0;
}

static void
clean_basic_block(basicblock *bb, int prev_lineno) {
Expand Down
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