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bpo-42246: Remove DO_NOT_EMIT_BYTECODE macros, so that while loops and if statements conform to PEP 626. #23743

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Merged
merged 2 commits into from
Dec 15, 2020
Merged

bpo-42246: Remove DO_NOT_EMIT_BYTECODE macros, so that while loops and if statements conform to PEP 626. #23743

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a239d48
Remove DO_NOT_EMIT_BYTECODE macros, so that while loops and if statem…
markshannon Dec 11, 2020
c15f5ab
Delete the macros.
markshannon Dec 14, 2020
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8 changes: 4 additions & 4 deletions Lib/test/test_compile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -728,10 +728,10 @@ def unused_block_while_else():

for func in funcs:
opcodes = list(dis.get_instructions(func))
self.assertEqual(2, len(opcodes))
self.assertEqual('LOAD_CONST', opcodes[0].opname)
self.assertEqual(None, opcodes[0].argval)
self.assertEqual('RETURN_VALUE', opcodes[1].opname)
self.assertLessEqual(len(opcodes), 3)
self.assertEqual('LOAD_CONST', opcodes[-2].opname)
self.assertEqual(None, opcodes[-2].argval)
self.assertEqual('RETURN_VALUE', opcodes[-1].opname)

def test_false_while_loop(self):
def break_in_while():
Expand Down
137 changes: 71 additions & 66 deletions Lib/test/test_dis.py
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15 changes: 0 additions & 15 deletions Lib/test/test_peepholer.py
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Expand Up @@ -409,21 +409,6 @@ def f(cond1, cond2):
self.assertLessEqual(len(returns), 6)
self.check_lnotab(f)

def test_elim_jump_after_return2(self):
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I've removed this test, as doesn't test what it claims to test. There is no dead code in

def f(cond1, cond2):
    while 1:
        if cond1: return 4

# Eliminate dead code: jumps immediately after returns can't be reached
def f(cond1, cond2):
while 1:
if cond1: return 4
self.assertNotInBytecode(f, 'JUMP_FORWARD')
# There should be one jump for the while loop.
jumps = [instr for instr in dis.get_instructions(f)
if 'JUMP' in instr.opname]
self.assertEqual(len(jumps), 1)
returns = [instr for instr in dis.get_instructions(f)
if instr.opname == 'RETURN_VALUE']
self.assertLessEqual(len(returns), 2)
self.check_lnotab(f)

def test_make_function_doesnt_bail(self):
def f():
def g()->1+1:
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12 changes: 9 additions & 3 deletions Lib/test/test_sys_settrace.py
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Expand Up @@ -53,9 +53,8 @@ def basic():
# following that clause?


# Some constructs like "while 0:", "if 0:" or "if 1:...else:..." are optimized
# away. No code # exists for them, so the line numbers skip directly from
# "del x" to "x = 1".
# Some constructs like "while 0:", "if 0:" or "if 1:...else:..." could be optimized
# away. Make sure that those lines aren't skipped.
def arigo_example0():
x = 1
del x
Expand All @@ -66,6 +65,7 @@ def arigo_example0():
arigo_example0.events = [(0, 'call'),
(1, 'line'),
(2, 'line'),
(3, 'line'),
(5, 'line'),
(5, 'return')]

Expand All @@ -79,6 +79,7 @@ def arigo_example1():
arigo_example1.events = [(0, 'call'),
(1, 'line'),
(2, 'line'),
(3, 'line'),
(5, 'line'),
(5, 'return')]

Expand All @@ -94,6 +95,7 @@ def arigo_example2():
arigo_example2.events = [(0, 'call'),
(1, 'line'),
(2, 'line'),
(3, 'line'),
(4, 'line'),
(7, 'line'),
(7, 'return')]
Expand Down Expand Up @@ -236,9 +238,13 @@ def tightloop_example():
(1, 'line'),
(2, 'line'),
(3, 'line'),
(4, 'line'),
(5, 'line'),
(4, 'line'),
(5, 'line'),
(4, 'line'),
(5, 'line'),
(4, 'line'),
(5, 'line'),
(5, 'exception'),
(6, 'line'),
Expand Down
112 changes: 27 additions & 85 deletions Python/compile.c
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Expand Up @@ -228,7 +228,7 @@ static int compiler_slice(struct compiler *, expr_ty);

static int inplace_binop(operator_ty);
static int are_all_items_const(asdl_expr_seq *, Py_ssize_t, Py_ssize_t);
static int expr_constant(expr_ty);


static int compiler_with(struct compiler *, stmt_ty, int);
static int compiler_async_with(struct compiler *, stmt_ty, int);
Expand Down Expand Up @@ -1572,17 +1572,6 @@ compiler_addop_j(struct compiler *c, int opcode, basicblock *b)
} \
}

/* These macros allows to check only for errors and not emmit bytecode
* while visiting nodes.
*/

#define BEGIN_DO_NOT_EMIT_BYTECODE { \
c->c_do_not_emit_bytecode++;

#define END_DO_NOT_EMIT_BYTECODE \
c->c_do_not_emit_bytecode--; \
}

/* Search if variable annotations are present statically in a block. */

static int
Expand Down Expand Up @@ -2704,48 +2693,28 @@ static int
compiler_if(struct compiler *c, stmt_ty s)
{
basicblock *end, *next;
int constant;
assert(s->kind == If_kind);
end = compiler_new_block(c);
if (end == NULL)
if (end == NULL) {
return 0;

constant = expr_constant(s->v.If.test);
/* constant = 0: "if 0"
* constant = 1: "if 1", "if 2", ...
* constant = -1: rest */
if (constant == 0) {
BEGIN_DO_NOT_EMIT_BYTECODE
VISIT_SEQ(c, stmt, s->v.If.body);
END_DO_NOT_EMIT_BYTECODE
if (s->v.If.orelse) {
VISIT_SEQ(c, stmt, s->v.If.orelse);
}
} else if (constant == 1) {
VISIT_SEQ(c, stmt, s->v.If.body);
if (s->v.If.orelse) {
BEGIN_DO_NOT_EMIT_BYTECODE
VISIT_SEQ(c, stmt, s->v.If.orelse);
END_DO_NOT_EMIT_BYTECODE
}
} else {
if (asdl_seq_LEN(s->v.If.orelse)) {
next = compiler_new_block(c);
if (next == NULL)
return 0;
}
else {
next = end;
}
if (!compiler_jump_if(c, s->v.If.test, next, 0)) {
}
if (asdl_seq_LEN(s->v.If.orelse)) {
next = compiler_new_block(c);
if (next == NULL) {
return 0;
}
VISIT_SEQ(c, stmt, s->v.If.body);
if (asdl_seq_LEN(s->v.If.orelse)) {
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, next);
VISIT_SEQ(c, stmt, s->v.If.orelse);
}
}
else {
next = end;
}
if (!compiler_jump_if(c, s->v.If.test, next, 0)) {
return 0;
}
VISIT_SEQ(c, stmt, s->v.If.body);
if (asdl_seq_LEN(s->v.If.orelse)) {
ADDOP_JUMP(c, JUMP_FORWARD, end);
compiler_use_next_block(c, next);
VISIT_SEQ(c, stmt, s->v.If.orelse);
}
compiler_use_next_block(c, end);
return 1;
Expand Down Expand Up @@ -2842,25 +2811,6 @@ static int
compiler_while(struct compiler *c, stmt_ty s)
{
basicblock *loop, *body, *end, *anchor = NULL;
int constant = expr_constant(s->v.While.test);

if (constant == 0) {
BEGIN_DO_NOT_EMIT_BYTECODE
// Push a dummy block so the VISIT_SEQ knows that we are
// inside a while loop so it can correctly evaluate syntax
// errors.
if (!compiler_push_fblock(c, WHILE_LOOP, NULL, NULL, NULL)) {
return 0;
}
VISIT_SEQ(c, stmt, s->v.While.body);
// Remove the dummy block now that is not needed.
compiler_pop_fblock(c, WHILE_LOOP, NULL);
END_DO_NOT_EMIT_BYTECODE
if (s->v.While.orelse) {
VISIT_SEQ(c, stmt, s->v.While.orelse);
}
return 1;
}
loop = compiler_new_block(c);
body = compiler_new_block(c);
anchor = compiler_new_block(c);
Expand All @@ -2872,15 +2822,16 @@ compiler_while(struct compiler *c, stmt_ty s)
if (!compiler_push_fblock(c, WHILE_LOOP, loop, end, NULL)) {
return 0;
}
if (constant == -1) {
if (!compiler_jump_if(c, s->v.While.test, anchor, 0)) {
return 0;
}
if (!compiler_jump_if(c, s->v.While.test, anchor, 0)) {
return 0;
}

compiler_use_next_block(c, body);
VISIT_SEQ(c, stmt, s->v.While.body);
ADDOP_JUMP(c, JUMP_ABSOLUTE, loop);
SET_LOC(c, s);
if (!compiler_jump_if(c, s->v.While.test, body, 1)) {
return 0;
}

compiler_pop_fblock(c, WHILE_LOOP, loop);

Expand Down Expand Up @@ -4791,15 +4742,6 @@ compiler_visit_keyword(struct compiler *c, keyword_ty k)
Return values: 1 for true, 0 for false, -1 for non-constant.
*/

static int
expr_constant(expr_ty e)
{
if (e->kind == Constant_kind) {
return PyObject_IsTrue(e->v.Constant.value);
}
return -1;
}

static int
compiler_with_except_finish(struct compiler *c) {
basicblock *exit;
Expand Down Expand Up @@ -6304,7 +6246,7 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
case JUMP_FORWARD:
if (inst->i_target != target->i_target) {
inst->i_target = target->i_target;
--i;
// --i;
}
break;
case JUMP_ABSOLUTE:
Expand All @@ -6317,8 +6259,8 @@ optimize_basic_block(basicblock *bb, PyObject *consts)
}
if (inst->i_target->b_exit && inst->i_target->b_iused <= MAX_COPY_SIZE) {
basicblock *to_copy = inst->i_target;
*inst = to_copy->b_instr[0];
for (i = 1; i < to_copy->b_iused; i++) {
inst->i_opcode = NOP;
for (i = 0; i < to_copy->b_iused; i++) {
int index = compiler_next_instr(bb);
if (index < 0) {
return -1;
Expand Down
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