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gh-106529: Make FOR_ITER a viable uop (#112134)

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This uses the new mechanism whereby certain uops
are replaced by others during translation,
using the `_PyUop_Replacements` table.
We further special-case the `_FOR_ITER_TIER_TWO` uop
to update the deoptimization target to point
just past the corresponding `END_FOR` opcode.

Two tiny code cleanups are also part of this PR.
This commit is contained in:
Guido van Rossum 2023-11-20 10:08:53 -08:00 • committed by GitHub
parent d59feb5dbe
commit 1995955173
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GPG key ID: 4AEE18F83AFDEB23
8 changed files with 138 additions and 43 deletions
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6
Python/abstract_interp_cases.c.h generated
View file

@ -624,6 +624,12 @@
break;
}
case _FOR_ITER_TIER_TWO: {
STACK_GROW(1);
PARTITIONNODE_OVERWRITE((_Py_PARTITIONNODE_t *)PARTITIONNODE_NULLROOT, PEEK(-(-1)), true);
break;
}
case _ITER_CHECK_LIST: {
break;
}

23
Python/bytecodes.c
View file

@ -2369,7 +2369,7 @@ dummy_func(
goto enter_tier_one;
}
replaced op(_POP_JUMP_IF_FALSE, (unused/1, cond -- )) {
replaced op(_POP_JUMP_IF_FALSE, (unused/1, cond -- )) {
assert(PyBool_Check(cond));
int flag = Py_IsFalse(cond);
#if ENABLE_SPECIALIZATION
@ -2513,7 +2513,7 @@ dummy_func(
#endif /* ENABLE_SPECIALIZATION */
}
op(_FOR_ITER, (iter -- iter, next)) {
replaced op(_FOR_ITER, (iter -- iter, next)) {
/* before: [iter]; after: [iter, iter()] *or* [] (and jump over END_FOR.) */
next = (*Py_TYPE(iter)->tp_iternext)(iter);
if (next == NULL) {
@ -2536,6 +2536,25 @@ dummy_func(
// Common case: no jump, leave it to the code generator
}
op(_FOR_ITER_TIER_TWO, (iter -- iter, next)) {
/* before: [iter]; after: [iter, iter()] *or* [] (and jump over END_FOR.) */
next = (*Py_TYPE(iter)->tp_iternext)(iter);
if (next == NULL) {
if (_PyErr_Occurred(tstate)) {
if (!_PyErr_ExceptionMatches(tstate, PyExc_StopIteration)) {
GOTO_ERROR(error);
}
_PyErr_Clear(tstate);
}
/* iterator ended normally */
Py_DECREF(iter);
STACK_SHRINK(1);
/* The translator sets the deopt target just past END_FOR */
DEOPT_IF(true);
}
// Common case: no jump, leave it to the code generator
}
macro(FOR_ITER) = _SPECIALIZE_FOR_ITER + _FOR_ITER;
inst(INSTRUMENTED_FOR_ITER, (unused/1 -- )) {

4
Python/ceval.c
View file

@ -1074,7 +1074,7 @@ deoptimize:
UOP_STAT_INC(opcode, miss);
frame->return_offset = 0; // Dispatch to frame->instr_ptr
_PyFrame_SetStackPointer(frame, stack_pointer);
frame->instr_ptr = next_uop[-1].target + _PyCode_CODE((PyCodeObject *)frame->f_executable);
frame->instr_ptr = next_uop[-1].target + _PyCode_CODE(_PyFrame_GetCode(frame));
Py_DECREF(current_executor);
// Fall through
// Jump here from ENTER_EXECUTOR
@ -1085,7 +1085,7 @@ enter_tier_one:
// Jump here from _EXIT_TRACE
exit_trace:
_PyFrame_SetStackPointer(frame, stack_pointer);
frame->instr_ptr = next_uop[-1].target + _PyCode_CODE((PyCodeObject *)frame->f_executable);
frame->instr_ptr = next_uop[-1].target + _PyCode_CODE(_PyFrame_GetCode(frame));
Py_DECREF(current_executor);
OPT_HIST(trace_uop_execution_counter, trace_run_length_hist);
goto enter_tier_one;

25
Python/executor_cases.c.h generated
View file

@ -2101,6 +2101,31 @@
break;
}
case _FOR_ITER_TIER_TWO: {
PyObject *iter;
PyObject *next;
iter = stack_pointer[-1];
/* before: [iter]; after: [iter, iter()] *or* [] (and jump over END_FOR.) */
next = (*Py_TYPE(iter)->tp_iternext)(iter);
if (next == NULL) {
if (_PyErr_Occurred(tstate)) {
if (!_PyErr_ExceptionMatches(tstate, PyExc_StopIteration)) {
GOTO_ERROR(error);
}
_PyErr_Clear(tstate);
}
/* iterator ended normally */
Py_DECREF(iter);
STACK_SHRINK(1);
/* The translator sets the deopt target just past END_FOR */
DEOPT_IF(true, _FOR_ITER_TIER_TWO);
}
// Common case: no jump, leave it to the code generator
STACK_GROW(1);
stack_pointer[-1] = next;
break;
}
case _ITER_CHECK_LIST: {
PyObject *iter;
iter = stack_pointer[-1];

6
Python/optimizer.c
View file

@ -392,6 +392,7 @@ _PyUop_Replacements[OPCODE_METADATA_SIZE] = {
[_ITER_JUMP_RANGE] = _GUARD_NOT_EXHAUSTED_RANGE,
[_ITER_JUMP_LIST] = _GUARD_NOT_EXHAUSTED_LIST,
[_ITER_JUMP_TUPLE] = _GUARD_NOT_EXHAUSTED_TUPLE,
[_FOR_ITER] = _FOR_ITER_TIER_TWO,
};
static const uint16_t
@ -620,6 +621,11 @@ top: // Jump here after _PUSH_FRAME or likely branches
}
if (_PyUop_Replacements[uop]) {
uop = _PyUop_Replacements[uop];
if (uop == _FOR_ITER_TIER_TWO) {
target += 1 + INLINE_CACHE_ENTRIES_FOR_ITER + oparg + 1;
assert(_PyCode_CODE(code)[target-1].op.code == END_FOR ||
_PyCode_CODE(code)[target-1].op.code == INSTRUMENTED_END_FOR);
}
}
break;
case OPARG_CACHE_1: