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Produce cleaner bytecode for 'with' and 'async with' by generating separate code for normal and exceptional paths. (#6641)

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Remove BEGIN_FINALLY, END_FINALLY, CALL_FINALLY and POP_FINALLY bytecodes. Implement finally blocks by code duplication.
Reimplement frame.lineno setter using line numbers rather than bytecode offsets.
This commit is contained in:
Mark Shannon 2019-11-21 09:11:43 +00:00 • committed by GitHub
parent 5dcc06f6e0
commit fee552669f
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GPG key ID: 4AEE18F83AFDEB23
15 changed files with 4789 additions and 4754 deletions
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222
Python/ceval.c
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@ -79,7 +79,7 @@ static PyObject * unicode_concatenate(PyThreadState *, PyObject *, PyObject *,
static PyObject * special_lookup(PyThreadState *, PyObject *, _Py_Identifier *);
static int check_args_iterable(PyThreadState *, PyObject *func, PyObject *vararg);
static void format_kwargs_error(PyThreadState *, PyObject *func, PyObject *kwargs);
static void format_awaitable_error(PyThreadState *, PyTypeObject *, int);
static void format_awaitable_error(PyThreadState *, PyTypeObject *, int, int);
#define NAME_ERROR_MSG \
"name '%.200s' is not defined"
@ -2017,7 +2017,12 @@ main_loop:
PyObject *iter = _PyCoro_GetAwaitableIter(iterable);
if (iter == NULL) {
int opcode_at_minus_3 = 0;
if ((next_instr - first_instr) > 2) {
opcode_at_minus_3 = _Py_OPCODE(next_instr[-3]);
}
format_awaitable_error(tstate, Py_TYPE(iterable),
opcode_at_minus_3,
_Py_OPCODE(next_instr[-2]));
}
@ -2128,104 +2133,13 @@ main_loop:
DISPATCH();
}
case TARGET(POP_FINALLY): {
/* If oparg is 0 at the top of the stack are 1 or 6 values:
Either:
- TOP = NULL or an integer
or:
- (TOP, SECOND, THIRD) = exc_info()
- (FOURTH, FITH, SIXTH) = previous exception for EXCEPT_HANDLER
If oparg is 1 the value for 'return' was additionally pushed
at the top of the stack.
*/
PyObject *res = NULL;
if (oparg) {
res = POP();
}
case TARGET(RERAISE): {
PyObject *exc = POP();
if (exc == NULL || PyLong_CheckExact(exc)) {
Py_XDECREF(exc);
}
else {
Py_DECREF(exc);
Py_DECREF(POP());
Py_DECREF(POP());
PyObject *type, *value, *traceback;
_PyErr_StackItem *exc_info;
PyTryBlock *b = PyFrame_BlockPop(f);
if (b->b_type != EXCEPT_HANDLER) {
_PyErr_SetString(tstate, PyExc_SystemError,
"popped block is not an except handler");
Py_XDECREF(res);
goto error;
}
assert(STACK_LEVEL() == (b)->b_level + 3);
exc_info = tstate->exc_info;
type = exc_info->exc_type;
value = exc_info->exc_value;
traceback = exc_info->exc_traceback;
exc_info->exc_type = POP();
exc_info->exc_value = POP();
exc_info->exc_traceback = POP();
Py_XDECREF(type);
Py_XDECREF(value);
Py_XDECREF(traceback);
}
if (oparg) {
PUSH(res);
}
DISPATCH();
}
case TARGET(CALL_FINALLY): {
PyObject *ret = PyLong_FromLong(INSTR_OFFSET());
if (ret == NULL) {
goto error;
}
PUSH(ret);
JUMPBY(oparg);
FAST_DISPATCH();
}
case TARGET(BEGIN_FINALLY): {
/* Push NULL onto the stack for using it in END_FINALLY,
POP_FINALLY, WITH_CLEANUP_START and WITH_CLEANUP_FINISH.
*/
PUSH(NULL);
FAST_DISPATCH();
}
case TARGET(END_FINALLY): {
PREDICTED(END_FINALLY);
/* At the top of the stack are 1 or 6 values:
Either:
- TOP = NULL or an integer
or:
- (TOP, SECOND, THIRD) = exc_info()
- (FOURTH, FITH, SIXTH) = previous exception for EXCEPT_HANDLER
*/
PyObject *exc = POP();
if (exc == NULL) {
FAST_DISPATCH();
}
else if (PyLong_CheckExact(exc)) {
int ret = _PyLong_AsInt(exc);
Py_DECREF(exc);
if (ret == -1 && _PyErr_Occurred(tstate)) {
goto error;
}
JUMPTO(ret);
FAST_DISPATCH();
}
else {
assert(PyExceptionClass_Check(exc));
PyObject *val = POP();
PyObject *tb = POP();
_PyErr_Restore(tstate, exc, val, tb);
goto exception_unwind;
}
PyObject *val = POP();
PyObject *tb = POP();
assert(PyExceptionClass_Check(exc));
PyErr_Restore(exc, val, tb);
goto exception_unwind;
}
case TARGET(END_ASYNC_FOR): {
@ -3302,111 +3216,31 @@ main_loop:
DISPATCH();
}
case TARGET(WITH_CLEANUP_START): {
/* At the top of the stack are 1 or 6 values indicating
how/why we entered the finally clause:
- TOP = NULL
case TARGET(WITH_EXCEPT_START): {
/* At the top of the stack are 7 values:
- (TOP, SECOND, THIRD) = exc_info()
(FOURTH, FITH, SIXTH) = previous exception for EXCEPT_HANDLER
Below them is EXIT, the context.__exit__ or context.__aexit__
bound method.
In the first case, we must call
EXIT(None, None, None)
otherwise we must call
EXIT(TOP, SECOND, THIRD)
In the first case, we remove EXIT from the
stack, leaving TOP, and push TOP on the stack.
Otherwise we shift the bottom 3 values of the
stack down, replace the empty spot with NULL, and push
None on the stack.
Finally we push the result of the call.
- (FOURTH, FIFTH, SIXTH) = previous exception for EXCEPT_HANDLER
- SEVENTH: the context.__exit__ bound method
We call SEVENTH(TOP, SECOND, THIRD).
Then we push again the TOP exception and the __exit__
return value.
*/
PyObject *exit_func;
PyObject *exc, *val, *tb, *res;
val = tb = Py_None;
exc = TOP();
if (exc == NULL) {
STACK_SHRINK(1);
exit_func = TOP();
SET_TOP(exc);
exc = Py_None;
}
else {
assert(PyExceptionClass_Check(exc));
PyObject *tp2, *exc2, *tb2;
PyTryBlock *block;
val = SECOND();
tb = THIRD();
tp2 = FOURTH();
exc2 = PEEK(5);
tb2 = PEEK(6);
exit_func = PEEK(7);
SET_VALUE(7, tb2);
SET_VALUE(6, exc2);
SET_VALUE(5, tp2);
/* UNWIND_EXCEPT_HANDLER will pop this off. */
SET_FOURTH(NULL);
/* We just shifted the stack down, so we have
to tell the except handler block that the
values are lower than it expects. */
assert(f->f_iblock > 0);
block = &f->f_blockstack[f->f_iblock - 1];
assert(block->b_type == EXCEPT_HANDLER);
assert(block->b_level > 0);
block->b_level--;
}
val = SECOND();
tb = THIRD();
assert(exc != Py_None);
assert(!PyLong_Check(exc));
exit_func = PEEK(7);
PyObject *stack[4] = {NULL, exc, val, tb};
res = _PyObject_Vectorcall(exit_func, stack + 1,
3 | PY_VECTORCALL_ARGUMENTS_OFFSET, NULL);
Py_DECREF(exit_func);
if (res == NULL)
goto error;
Py_INCREF(exc); /* Duplicating the exception on the stack */
PUSH(exc);
PUSH(res);
PREDICT(WITH_CLEANUP_FINISH);
DISPATCH();
}
case TARGET(WITH_CLEANUP_FINISH): {
PREDICTED(WITH_CLEANUP_FINISH);
/* TOP = the result of calling the context.__exit__ bound method
SECOND = either None or exception type
If SECOND is None below is NULL or the return address,
otherwise below are 7 values representing an exception.
*/
PyObject *res = POP();
PyObject *exc = POP();
int err;
if (exc != Py_None)
err = PyObject_IsTrue(res);
else
err = 0;
Py_DECREF(res);
Py_DECREF(exc);
if (err < 0)
goto error;
else if (err > 0) {
/* There was an exception and a True return.
* We must manually unwind the EXCEPT_HANDLER block
* which was created when the exception was caught,
* otherwise the stack will be in an inconsistent state.
*/
PyTryBlock *b = PyFrame_BlockPop(f);
assert(b->b_type == EXCEPT_HANDLER);
UNWIND_EXCEPT_HANDLER(b);
PUSH(NULL);
}
PREDICT(END_FINALLY);
DISPATCH();
}
@ -3776,6 +3610,10 @@ exception_unwind:
PUSH(val);
PUSH(exc);
JUMPTO(handler);
if (_Py_TracingPossible(ceval)) {
/* Make sure that we trace line after exception */
instr_prev = INT_MAX;
}
/* Resume normal execution */
goto main_loop;
}
@ -5477,7 +5315,7 @@ format_exc_unbound(PyThreadState *tstate, PyCodeObject *co, int oparg)
}
static void
format_awaitable_error(PyThreadState *tstate, PyTypeObject *type, int prevopcode)
format_awaitable_error(PyThreadState *tstate, PyTypeObject *type, int prevprevopcode, int prevopcode)
{
if (type->tp_as_async == NULL || type->tp_as_async->am_await == NULL) {
if (prevopcode == BEFORE_ASYNC_WITH) {
@ -5486,7 +5324,7 @@ format_awaitable_error(PyThreadState *tstate, PyTypeObject *type, int prevopcode
"that does not implement __await__: %.100s",
type->tp_name);
}
else if (prevopcode == WITH_CLEANUP_START) {
else if (prevopcode == WITH_EXCEPT_START || (prevopcode == CALL_FUNCTION && prevprevopcode == DUP_TOP)) {
_PyErr_Format(tstate, PyExc_TypeError,
"'async with' received an object from __aexit__ "
"that does not implement __await__: %.100s",