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GH-118093: Handle some polymorphism before requiring progress in tier two (GH-122843)

This commit is contained in:
Brandt Bucher 2024-08-12 12:39:31 -07:00 committed by GitHub
parent 503af8fe9a
commit 9621a7d017
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GPG Key ID: B5690EEEBB952194
6 changed files with 73 additions and 42 deletions
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15
Include/internal/pycore_optimizer.h
View File

@ -29,8 +29,9 @@ typedef struct {
typedef struct {
uint8_t opcode;
uint8_t oparg;
uint8_t valid;
uint8_t linked;
uint16_t valid:1;
uint16_t linked:1;
uint16_t chain_depth:14; // Must be big engough for MAX_CHAIN_DEPTH - 1.
int index; // Index of ENTER_EXECUTOR (if code isn't NULL, below).
_PyBloomFilter bloom;
_PyExecutorLinkListNode links;
@ -83,7 +84,7 @@ typedef struct _PyOptimizerObject _PyOptimizerObject;
typedef int (*_Py_optimize_func)(
_PyOptimizerObject* self, struct _PyInterpreterFrame *frame,
_Py_CODEUNIT *instr, _PyExecutorObject **exec_ptr,
int curr_stackentries);
int curr_stackentries, bool progress_needed);
struct _PyOptimizerObject {
PyObject_HEAD
@ -182,6 +183,12 @@ static inline uint16_t uop_get_error_target(const _PyUOpInstruction *inst)
// Need extras for root frame and for overflow frame (see TRACE_STACK_PUSH())
#define MAX_ABSTRACT_FRAME_DEPTH (TRACE_STACK_SIZE + 2)
// The maximum number of side exits that we can take before requiring forward
// progress (and inserting a new ENTER_EXECUTOR instruction). In practice, this
// is the "maximum amount of polymorphism" that an isolated trace tree can
// handle before rejoining the rest of the program.
#define MAX_CHAIN_DEPTH 4
typedef struct _Py_UopsSymbol _Py_UopsSymbol;
struct _Py_UOpsAbstractFrame {
@ -257,7 +264,7 @@ extern int _Py_uop_frame_pop(_Py_UOpsContext *ctx);
PyAPI_FUNC(PyObject *) _Py_uop_symbols_test(PyObject *self, PyObject *ignored);
PyAPI_FUNC(int) _PyOptimizer_Optimize(struct _PyInterpreterFrame *frame, _Py_CODEUNIT *start, _PyStackRef *stack_pointer, _PyExecutorObject **exec_ptr);
PyAPI_FUNC(int) _PyOptimizer_Optimize(struct _PyInterpreterFrame *frame, _Py_CODEUNIT *start, _PyStackRef *stack_pointer, _PyExecutorObject **exec_ptr, int chain_depth);
static inline int is_terminator(const _PyUOpInstruction *uop)
{

1
Misc/NEWS.d/next/Core_and_Builtins/2024-08-08-16-02-28.gh-issue-118093.m6Mrvy.rst Normal file
View File

@ -0,0 +1 @@
Improve the experimental JIT's handling of polymorphic code.

7
Python/bytecodes.c
View File

@ -2501,7 +2501,7 @@ dummy_func(
start--;
}
_PyExecutorObject *executor;
int optimized = _PyOptimizer_Optimize(frame, start, stack_pointer, &executor);
int optimized = _PyOptimizer_Optimize(frame, start, stack_pointer, &executor, 0);
ERROR_IF(optimized < 0, error);
if (optimized) {
assert(tstate->previous_executor == NULL);
@ -4543,7 +4543,8 @@ dummy_func(
Py_INCREF(executor);
}
else {
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor);
int chain_depth = current_executor->vm_data.chain_depth + 1;
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor, chain_depth);
if (optimized <= 0) {
exit->temperature = restart_backoff_counter(temperature);
if (optimized < 0) {
@ -4626,7 +4627,7 @@ dummy_func(
exit->temperature = advance_backoff_counter(exit->temperature);
GOTO_TIER_ONE(target);
}
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor);
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor, 0);
if (optimized <= 0) {
exit->temperature = restart_backoff_counter(exit->temperature);
if (optimized < 0) {

5
Python/executor_cases.c.h generated
View File

@ -5015,7 +5015,8 @@
Py_INCREF(executor);
}
else {
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor);
int chain_depth = current_executor->vm_data.chain_depth + 1;
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor, chain_depth);
if (optimized <= 0) {
exit->temperature = restart_backoff_counter(temperature);
if (optimized < 0) {
@ -5147,7 +5148,7 @@
exit->temperature = advance_backoff_counter(exit->temperature);
GOTO_TIER_ONE(target);
}
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor);
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor, 0);
if (optimized <= 0) {
exit->temperature = restart_backoff_counter(exit->temperature);
if (optimized < 0) {

2
Python/generated_cases.c.h generated
View File

@ -4259,7 +4259,7 @@
start--;
}
_PyExecutorObject *executor;
int optimized = _PyOptimizer_Optimize(frame, start, stack_pointer, &executor);
int optimized = _PyOptimizer_Optimize(frame, start, stack_pointer, &executor, 0);
if (optimized < 0) goto error;
if (optimized) {
assert(tstate->previous_executor == NULL);

85
Python/optimizer.c
View File

@ -111,7 +111,8 @@ never_optimize(
_PyInterpreterFrame *frame,
_Py_CODEUNIT *instr,
_PyExecutorObject **exec,
int Py_UNUSED(stack_entries))
int Py_UNUSED(stack_entries),
bool Py_UNUSED(progress_needed))
{
// This may be called if the optimizer is reset
return 0;
@ -176,32 +177,44 @@ _Py_SetTier2Optimizer(_PyOptimizerObject *optimizer)
int
_PyOptimizer_Optimize(
_PyInterpreterFrame *frame, _Py_CODEUNIT *start,
_PyStackRef *stack_pointer, _PyExecutorObject **executor_ptr)
_PyStackRef *stack_pointer, _PyExecutorObject **executor_ptr, int chain_depth)
{
// The first executor in a chain and the MAX_CHAIN_DEPTH'th executor *must*
// make progress in order to avoid infinite loops or excessively-long
// side-exit chains. We can only insert the executor into the bytecode if
// this is true, since a deopt won't infinitely re-enter the executor:
chain_depth %= MAX_CHAIN_DEPTH;
bool progress_needed = chain_depth == 0;
PyCodeObject *code = _PyFrame_GetCode(frame);
assert(PyCode_Check(code));
PyInterpreterState *interp = _PyInterpreterState_GET();
if (!has_space_for_executor(code, start)) {
if (progress_needed && !has_space_for_executor(code, start)) {
return 0;
}
_PyOptimizerObject *opt = interp->optimizer;
int err = opt->optimize(opt, frame, start, executor_ptr, (int)(stack_pointer - _PyFrame_Stackbase(frame)));
int err = opt->optimize(opt, frame, start, executor_ptr, (int)(stack_pointer - _PyFrame_Stackbase(frame)), progress_needed);
if (err <= 0) {
return err;
}
assert(*executor_ptr != NULL);
int index = get_index_for_executor(code, start);
if (index < 0) {
/* Out of memory. Don't raise and assume that the
* error will show up elsewhere.
*
* If an optimizer has already produced an executor,
* it might get confused by the executor disappearing,
* but there is not much we can do about that here. */
Py_DECREF(*executor_ptr);
return 0;
if (progress_needed) {
int index = get_index_for_executor(code, start);
if (index < 0) {
/* Out of memory. Don't raise and assume that the
* error will show up elsewhere.
*
* If an optimizer has already produced an executor,
* it might get confused by the executor disappearing,
* but there is not much we can do about that here. */
Py_DECREF(*executor_ptr);
return 0;
}
insert_executor(code, start, index, *executor_ptr);
}
insert_executor(code, start, index, *executor_ptr);
else {
(*executor_ptr)->vm_data.code = NULL;
}
(*executor_ptr)->vm_data.chain_depth = chain_depth;
assert((*executor_ptr)->vm_data.valid);
return 1;
}
@ -530,9 +543,9 @@ translate_bytecode_to_trace(
_Py_CODEUNIT *instr,
_PyUOpInstruction *trace,
int buffer_size,
_PyBloomFilter *dependencies)
_PyBloomFilter *dependencies, bool progress_needed)
{
bool progress_needed = true;
bool first = true;
PyCodeObject *code = _PyFrame_GetCode(frame);
PyFunctionObject *func = (PyFunctionObject *)frame->f_funcobj;
assert(PyFunction_Check(func));
@ -576,7 +589,7 @@ translate_bytecode_to_trace(
uint32_t opcode = instr->op.code;
uint32_t oparg = instr->op.arg;
if (!progress_needed && instr == initial_instr) {
if (!first && instr == initial_instr) {
// We have looped around to the start:
RESERVE(1);
ADD_TO_TRACE(_JUMP_TO_TOP, 0, 0, 0);
@ -585,14 +598,6 @@ translate_bytecode_to_trace(
DPRINTF(2, "%d: %s(%d)\n", target, _PyOpcode_OpName[opcode], oparg);
if (opcode == ENTER_EXECUTOR) {
assert(oparg < 256);
_PyExecutorObject *executor = code->co_executors->executors[oparg];
opcode = executor->vm_data.opcode;
DPRINTF(2, " * ENTER_EXECUTOR -> %s\n", _PyOpcode_OpName[opcode]);
oparg = executor->vm_data.oparg;
}
if (opcode == EXTENDED_ARG) {
instr++;
opcode = instr->op.code;
@ -602,13 +607,27 @@ translate_bytecode_to_trace(
goto done;
}
}
if (opcode == ENTER_EXECUTOR) {
// We have a couple of options here. We *could* peek "underneath"
// this executor and continue tracing, which could give us a longer,
// more optimizeable trace (at the expense of lots of duplicated
// tier two code). Instead, we choose to just end here and stitch to
// the other trace, which allows a side-exit traces to rejoin the
// "main" trace periodically (and also helps protect us against
// pathological behavior where the amount of tier two code explodes
// for a medium-length, branchy code path). This seems to work
// better in practice, but in the future we could be smarter about
// what we do here:
goto done;
}
assert(opcode != ENTER_EXECUTOR && opcode != EXTENDED_ARG);
RESERVE_RAW(2, "_CHECK_VALIDITY_AND_SET_IP");
ADD_TO_TRACE(_CHECK_VALIDITY_AND_SET_IP, 0, (uintptr_t)instr, target);
/* Special case the first instruction,
* so that we can guarantee forward progress */
if (progress_needed) {
if (first && progress_needed) {
assert(first);
if (OPCODE_HAS_EXIT(opcode) || OPCODE_HAS_DEOPT(opcode)) {
opcode = _PyOpcode_Deopt[opcode];
}
@ -903,7 +922,7 @@ translate_bytecode_to_trace(
}
top:
// Jump here after _PUSH_FRAME or likely branches.
progress_needed = false;
first = false;
} // End for (;;)
done:
@ -912,7 +931,7 @@ done:
}
assert(code == initial_code);
// Skip short traces where we can't even translate a single instruction:
if (progress_needed) {
if (first) {
OPT_STAT_INC(trace_too_short);
DPRINTF(2,
"No trace for %s (%s:%d) at byte offset %d (no progress)\n",
@ -1225,13 +1244,14 @@ uop_optimize(
_PyInterpreterFrame *frame,
_Py_CODEUNIT *instr,
_PyExecutorObject **exec_ptr,
int curr_stackentries)
int curr_stackentries,
bool progress_needed)
{
_PyBloomFilter dependencies;
_Py_BloomFilter_Init(&dependencies);
_PyUOpInstruction buffer[UOP_MAX_TRACE_LENGTH];
OPT_STAT_INC(attempts);
int length = translate_bytecode_to_trace(frame, instr, buffer, UOP_MAX_TRACE_LENGTH, &dependencies);
int length = translate_bytecode_to_trace(frame, instr, buffer, UOP_MAX_TRACE_LENGTH, &dependencies, progress_needed);
if (length <= 0) {
// Error or nothing translated
return length;
@ -1328,7 +1348,8 @@ counter_optimize(
_PyInterpreterFrame *frame,
_Py_CODEUNIT *instr,
_PyExecutorObject **exec_ptr,
int Py_UNUSED(curr_stackentries)
int Py_UNUSED(curr_stackentries),
bool Py_UNUSED(progress_needed)
)
{
PyCodeObject *code = _PyFrame_GetCode(frame);