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cpython/Python/optimizer.c

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#include "Python.h"
#include "opcode.h"
#include "pycore_interp.h"
#include "pycore_bitutils.h" // _Py_popcount32()
#include "pycore_opcode_metadata.h" // _PyOpcode_OpName[]
#include "pycore_opcode_utils.h" // MAX_REAL_OPCODE
#include "pycore_optimizer.h" // _Py_uop_analyze_and_optimize()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "pycore_uop_ids.h"
#include "cpython/optimizer.h"
#include <stdbool.h>
#include <stdint.h>
#include <stddef.h>
#define NEED_OPCODE_METADATA
#include "pycore_uop_metadata.h" // Uop tables
#undef NEED_OPCODE_METADATA
#define UOP_MAX_TRACE_LENGTH 512
#define MAX_EXECUTORS_SIZE 256
static bool
has_space_for_executor(PyCodeObject *code, _Py_CODEUNIT *instr)
{
if (instr->op.code == ENTER_EXECUTOR) {
return true;
}
if (code->co_executors == NULL) {
return true;
}
return code->co_executors->size < MAX_EXECUTORS_SIZE;
}
static int32_t
get_index_for_executor(PyCodeObject *code, _Py_CODEUNIT *instr)
{
if (instr->op.code == ENTER_EXECUTOR) {
return instr->op.arg;
}
_PyExecutorArray *old = code->co_executors;
int size = 0;
int capacity = 0;
if (old != NULL) {
size = old->size;
capacity = old->capacity;
assert(size < MAX_EXECUTORS_SIZE);
}
assert(size <= capacity);
if (size == capacity) {
/* Array is full. Grow array */
int new_capacity = capacity ? capacity * 2 : 4;
_PyExecutorArray *new = PyMem_Realloc(
old,
offsetof(_PyExecutorArray, executors) +
new_capacity * sizeof(_PyExecutorObject *));
if (new == NULL) {
return -1;
}
new->capacity = new_capacity;
new->size = size;
code->co_executors = new;
}
assert(size < code->co_executors->capacity);
return size;
}
static void
insert_executor(PyCodeObject *code, _Py_CODEUNIT *instr, int index, _PyExecutorObject *executor)
{
Py_INCREF(executor);
if (instr->op.code == ENTER_EXECUTOR) {
assert(index == instr->op.arg);
_PyExecutorObject *old = code->co_executors->executors[index];
executor->vm_data.opcode = old->vm_data.opcode;
executor->vm_data.oparg = old->vm_data.oparg;
old->vm_data.opcode = 0;
code->co_executors->executors[index] = executor;
Py_DECREF(old);
}
else {
assert(code->co_executors->size == index);
assert(code->co_executors->capacity > index);
executor->vm_data.opcode = instr->op.code;
executor->vm_data.oparg = instr->op.arg;
code->co_executors->executors[index] = executor;
assert(index < MAX_EXECUTORS_SIZE);
instr->op.code = ENTER_EXECUTOR;
instr->op.arg = index;
code->co_executors->size++;
}
return;
}
int
PyUnstable_Replace_Executor(PyCodeObject *code, _Py_CODEUNIT *instr, _PyExecutorObject *new)
{
if (instr->op.code != ENTER_EXECUTOR) {
PyErr_Format(PyExc_ValueError, "No executor to replace");
return -1;
}
int index = instr->op.arg;
assert(index >= 0);
insert_executor(code, instr, index, new);
return 0;
}
static int
error_optimize(
_PyOptimizerObject* self,
PyCodeObject *code,
_Py_CODEUNIT *instr,
_PyExecutorObject **exec,
int Py_UNUSED(stack_entries))
{
assert(0);
PyErr_Format(PyExc_SystemError, "Should never call error_optimize");
return -1;
}
PyTypeObject _PyDefaultOptimizer_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
.tp_name = "noop_optimizer",
.tp_basicsize = sizeof(_PyOptimizerObject),
.tp_itemsize = 0,
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
};
_PyOptimizerObject _PyOptimizer_Default = {
PyObject_HEAD_INIT(&_PyDefaultOptimizer_Type)
.optimize = error_optimize,
.resume_threshold = INT16_MAX,
.backedge_threshold = INT16_MAX,
};
_PyOptimizerObject *
PyUnstable_GetOptimizer(void)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
if (interp->optimizer == &_PyOptimizer_Default) {
return NULL;
}
assert(interp->optimizer_backedge_threshold == interp->optimizer->backedge_threshold);
assert(interp->optimizer_resume_threshold == interp->optimizer->resume_threshold);
Py_INCREF(interp->optimizer);
return interp->optimizer;
}
void
PyUnstable_SetOptimizer(_PyOptimizerObject *optimizer)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
if (optimizer == NULL) {
optimizer = &_PyOptimizer_Default;
}
_PyOptimizerObject *old = interp->optimizer;
Py_INCREF(optimizer);
interp->optimizer = optimizer;
interp->optimizer_backedge_threshold = optimizer->backedge_threshold;
interp->optimizer_resume_threshold = optimizer->resume_threshold;
Py_DECREF(old);
}
int
_PyOptimizer_Optimize(_PyInterpreterFrame *frame, _Py_CODEUNIT *start, PyObject **stack_pointer)
{
PyCodeObject *code = (PyCodeObject *)frame->f_executable;
assert(PyCode_Check(code));
PyInterpreterState *interp = _PyInterpreterState_GET();
if (!has_space_for_executor(code, start)) {
return 0;
}
_PyOptimizerObject *opt = interp->optimizer;
_PyExecutorObject *executor = NULL;
int err = opt->optimize(opt, code, start, &executor, (int)(stack_pointer - _PyFrame_Stackbase(frame)));
if (err <= 0) {
assert(executor == NULL);
return err;
}
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);
return 0;
}
insert_executor(code, start, index, executor);
Py_DECREF(executor);
return 1;
}
_PyExecutorObject *
PyUnstable_GetExecutor(PyCodeObject *code, int offset)
{
int code_len = (int)Py_SIZE(code);
for (int i = 0 ; i < code_len;) {
if (_PyCode_CODE(code)[i].op.code == ENTER_EXECUTOR && i*2 == offset) {
int oparg = _PyCode_CODE(code)[i].op.arg;
_PyExecutorObject *res = code->co_executors->executors[oparg];
Py_INCREF(res);
return res;
}
i += _PyInstruction_GetLength(code, i);
}
PyErr_SetString(PyExc_ValueError, "no executor at given byte offset");
return NULL;
}
static PyObject *
is_valid(PyObject *self, PyObject *Py_UNUSED(ignored))
{
return PyBool_FromLong(((_PyExecutorObject *)self)->vm_data.valid);
}
static PyMethodDef executor_methods[] = {
{ "is_valid", is_valid, METH_NOARGS, NULL },
{ NULL, NULL },
};
///////////////////// Experimental UOp Optimizer /////////////////////
static void
uop_dealloc(_PyExecutorObject *self) {
_Py_ExecutorClear(self);
PyObject_Free(self);
}
const char *
_PyUOpName(int index)
{
return _PyOpcode_uop_name[index];
}
static Py_ssize_t
uop_len(_PyExecutorObject *self)
{
return Py_SIZE(self);
}
static PyObject *
uop_item(_PyExecutorObject *self, Py_ssize_t index)
{
Py_ssize_t len = uop_len(self);
if (index < 0 || index >= len) {
PyErr_SetNone(PyExc_IndexError);
return NULL;
}
const char *name = _PyUOpName(self->trace[index].opcode);
if (name == NULL) {
name = "<nil>";
}
PyObject *oname = _PyUnicode_FromASCII(name, strlen(name));
if (oname == NULL) {
return NULL;
}
PyObject *oparg = PyLong_FromUnsignedLong(self->trace[index].oparg);
if (oparg == NULL) {
Py_DECREF(oname);
return NULL;
}
PyObject *operand = PyLong_FromUnsignedLongLong(self->trace[index].operand);
if (operand == NULL) {
Py_DECREF(oparg);
Py_DECREF(oname);
return NULL;
}
PyObject *args[3] = { oname, oparg, operand };
return _PyTuple_FromArraySteal(args, 3);
}
PySequenceMethods uop_as_sequence = {
.sq_length = (lenfunc)uop_len,
.sq_item = (ssizeargfunc)uop_item,
};
PyTypeObject _PyUOpExecutor_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
.tp_name = "uop_executor",
.tp_basicsize = offsetof(_PyExecutorObject, trace),
.tp_itemsize = sizeof(_PyUOpInstruction),
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
.tp_dealloc = (destructor)uop_dealloc,
.tp_as_sequence = &uop_as_sequence,
.tp_methods = executor_methods,
};
/* TO DO -- Generate these tables */
static const uint16_t
_PyUOp_Replacements[MAX_UOP_ID + 1] = {
[_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
BRANCH_TO_GUARD[4][2] = {
[POP_JUMP_IF_FALSE - POP_JUMP_IF_FALSE][0] = _GUARD_IS_TRUE_POP,
[POP_JUMP_IF_FALSE - POP_JUMP_IF_FALSE][1] = _GUARD_IS_FALSE_POP,
[POP_JUMP_IF_TRUE - POP_JUMP_IF_FALSE][0] = _GUARD_IS_FALSE_POP,
[POP_JUMP_IF_TRUE - POP_JUMP_IF_FALSE][1] = _GUARD_IS_TRUE_POP,
[POP_JUMP_IF_NONE - POP_JUMP_IF_FALSE][0] = _GUARD_IS_NOT_NONE_POP,
[POP_JUMP_IF_NONE - POP_JUMP_IF_FALSE][1] = _GUARD_IS_NONE_POP,
[POP_JUMP_IF_NOT_NONE - POP_JUMP_IF_FALSE][0] = _GUARD_IS_NONE_POP,
[POP_JUMP_IF_NOT_NONE - POP_JUMP_IF_FALSE][1] = _GUARD_IS_NOT_NONE_POP,
};
#define TRACE_STACK_SIZE 5
#define CONFIDENCE_RANGE 1000
#define CONFIDENCE_CUTOFF 333
#ifdef Py_DEBUG
#define DPRINTF(level, ...) \
if (lltrace >= (level)) { printf(__VA_ARGS__); }
#else
#define DPRINTF(level, ...)
#endif
#define ADD_TO_TRACE(OPCODE, OPARG, OPERAND, TARGET) \
DPRINTF(2, \
" ADD_TO_TRACE(%s, %d, %" PRIu64 ")\n", \
_PyUOpName(OPCODE), \
(OPARG), \
(uint64_t)(OPERAND)); \
assert(trace_length < max_length); \
trace[trace_length].opcode = (OPCODE); \
trace[trace_length].oparg = (OPARG); \
trace[trace_length].operand = (OPERAND); \
trace[trace_length].target = (TARGET); \
trace_length++;
#define INSTR_IP(INSTR, CODE) \
((uint32_t)((INSTR) - ((_Py_CODEUNIT *)(CODE)->co_code_adaptive)))
// Reserve space for n uops
#define RESERVE_RAW(n, opname) \
if (trace_length + (n) > max_length) { \
DPRINTF(2, "No room for %s (need %d, got %d)\n", \
(opname), (n), max_length - trace_length); \
OPT_STAT_INC(trace_too_long); \
goto done; \
}
// Reserve space for N uops, plus 3 for _SET_IP, _CHECK_VALIDITY and _EXIT_TRACE
#define RESERVE(needed) RESERVE_RAW((needed) + 3, _PyUOpName(opcode))
// Trace stack operations (used by _PUSH_FRAME, _POP_FRAME)
#define TRACE_STACK_PUSH() \
if (trace_stack_depth >= TRACE_STACK_SIZE) { \
DPRINTF(2, "Trace stack overflow\n"); \
OPT_STAT_INC(trace_stack_overflow); \
ADD_TO_TRACE(_EXIT_TRACE, 0, 0, 0); \
goto done; \
} \
trace_stack[trace_stack_depth].code = code; \
trace_stack[trace_stack_depth].instr = instr; \
trace_stack_depth++;
#define TRACE_STACK_POP() \
if (trace_stack_depth <= 0) { \
Py_FatalError("Trace stack underflow\n"); \
} \
trace_stack_depth--; \
code = trace_stack[trace_stack_depth].code; \
instr = trace_stack[trace_stack_depth].instr;
/* Returns 1 on success,
* 0 if it failed to produce a worthwhile trace,
* and -1 on an error.
*/
static int
translate_bytecode_to_trace(
PyCodeObject *code,
_Py_CODEUNIT *instr,
_PyUOpInstruction *trace,
int buffer_size,
_PyBloomFilter *dependencies)
{
bool progress_needed = true;
PyCodeObject *initial_code = code;
_Py_BloomFilter_Add(dependencies, initial_code);
_Py_CODEUNIT *initial_instr = instr;
int trace_length = 0;
int max_length = buffer_size;
struct {
PyCodeObject *code;
_Py_CODEUNIT *instr;
} trace_stack[TRACE_STACK_SIZE];
int trace_stack_depth = 0;
int confidence = CONFIDENCE_RANGE; // Adjusted by branch instructions
#ifdef Py_DEBUG
char *python_lltrace = Py_GETENV("PYTHON_LLTRACE");
int lltrace = 0;
if (python_lltrace != NULL && *python_lltrace >= '0') {
lltrace = *python_lltrace - '0'; // TODO: Parse an int and all that
}
#endif
DPRINTF(4,
"Optimizing %s (%s:%d) at byte offset %d\n",
PyUnicode_AsUTF8(code->co_qualname),
PyUnicode_AsUTF8(code->co_filename),
code->co_firstlineno,
2 * INSTR_IP(initial_instr, code));
uint32_t target = 0;
top: // Jump here after _PUSH_FRAME or likely branches
for (;;) {
target = INSTR_IP(instr, code);
RESERVE_RAW(3, "epilogue"); // Always need space for _SET_IP, _CHECK_VALIDITY and _EXIT_TRACE
ADD_TO_TRACE(_SET_IP, target, 0, target);
ADD_TO_TRACE(_CHECK_VALIDITY, 0, 0, target);
uint32_t opcode = instr->op.code;
uint32_t oparg = instr->op.arg;
uint32_t extended = 0;
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++;
extended = 1;
opcode = instr->op.code;
oparg = (oparg << 8) | instr->op.arg;
if (opcode == EXTENDED_ARG) {
instr--;
goto done;
}
}
assert(opcode != ENTER_EXECUTOR && opcode != EXTENDED_ARG);
/* Special case the first instruction,
* so that we can guarantee forward progress */
if (progress_needed) {
progress_needed = false;
if (opcode == JUMP_BACKWARD || opcode == JUMP_BACKWARD_NO_INTERRUPT) {
instr += 1 + _PyOpcode_Caches[opcode] - (int32_t)oparg;
initial_instr = instr;
continue;
}
else {
if (OPCODE_HAS_DEOPT(opcode)) {
opcode = _PyOpcode_Deopt[opcode];
}
assert(!OPCODE_HAS_DEOPT(opcode));
}
}
switch (opcode) {
case POP_JUMP_IF_NONE:
case POP_JUMP_IF_NOT_NONE:
case POP_JUMP_IF_FALSE:
case POP_JUMP_IF_TRUE:
{
RESERVE(1);
int counter = instr[1].cache;
int bitcount = _Py_popcount32(counter);
int jump_likely = bitcount > 8;
if (jump_likely) {
confidence = confidence * bitcount / 16;
}
else {
confidence = confidence * (16 - bitcount) / 16;
}
if (confidence < CONFIDENCE_CUTOFF) {
DPRINTF(2, "Confidence too low (%d)\n", confidence);
OPT_STAT_INC(low_confidence);
goto done;
}
uint32_t uopcode = BRANCH_TO_GUARD[opcode - POP_JUMP_IF_FALSE][jump_likely];
DPRINTF(2, "%s(%d): counter=%x, bitcount=%d, likely=%d, confidence=%d, uopcode=%s\n",
_PyOpcode_OpName[opcode], oparg,
counter, bitcount, jump_likely, confidence, _PyUOpName(uopcode));
_Py_CODEUNIT *next_instr = instr + 1 + _PyOpcode_Caches[_PyOpcode_Deopt[opcode]];
_Py_CODEUNIT *target_instr = next_instr + oparg;
if (jump_likely) {
DPRINTF(2, "Jump likely (%x = %d bits), continue at byte offset %d\n",
instr[1].cache, bitcount, 2 * INSTR_IP(target_instr, code));
instr = target_instr;
ADD_TO_TRACE(uopcode, max_length, 0, INSTR_IP(next_instr, code));
goto top;
}
ADD_TO_TRACE(uopcode, max_length, 0, INSTR_IP(target_instr, code));
break;
}
case JUMP_BACKWARD:
case JUMP_BACKWARD_NO_INTERRUPT:
{
_Py_CODEUNIT *target = instr + 1 + _PyOpcode_Caches[opcode] - (int)oparg;
if (target == initial_instr) {
/* We have looped round to the start */
RESERVE(1);
ADD_TO_TRACE(_JUMP_TO_TOP, 0, 0, 0);
}
else {
OPT_STAT_INC(inner_loop);
DPRINTF(2, "JUMP_BACKWARD not to top ends trace\n");
}
goto done;
}
case JUMP_FORWARD:
{
RESERVE(0);
// This will emit two _SET_IP instructions; leave it to the optimizer
instr += oparg;
break;
}
default:
{
const struct opcode_macro_expansion *expansion = &_PyOpcode_macro_expansion[opcode];
if (expansion->nuops > 0) {
// Reserve space for nuops (+ _SET_IP + _EXIT_TRACE)
int nuops = expansion->nuops;
RESERVE(nuops);
if (expansion->uops[nuops-1].uop == _POP_FRAME) {
// Check for trace stack underflow now:
// We can't bail e.g. in the middle of
// LOAD_CONST + _POP_FRAME.
if (trace_stack_depth == 0) {
DPRINTF(2, "Trace stack underflow\n");
OPT_STAT_INC(trace_stack_underflow);
goto done;
}
}
uint32_t orig_oparg = oparg; // For OPARG_TOP/BOTTOM
for (int i = 0; i < nuops; i++) {
oparg = orig_oparg;
uint32_t uop = expansion->uops[i].uop;
uint64_t operand = 0;
// Add one to account for the actual opcode/oparg pair:
int offset = expansion->uops[i].offset + 1;
switch (expansion->uops[i].size) {
case OPARG_FULL:
assert(opcode != JUMP_BACKWARD_NO_INTERRUPT && opcode != JUMP_BACKWARD);
break;
case OPARG_CACHE_1:
operand = read_u16(&instr[offset].cache);
break;
case OPARG_CACHE_2:
operand = read_u32(&instr[offset].cache);
break;
case OPARG_CACHE_4:
operand = read_u64(&instr[offset].cache);
break;
case OPARG_TOP: // First half of super-instr
oparg = orig_oparg >> 4;
break;
case OPARG_BOTTOM: // Second half of super-instr
oparg = orig_oparg & 0xF;
break;
case OPARG_SAVE_RETURN_OFFSET: // op=_SAVE_RETURN_OFFSET; oparg=return_offset
oparg = offset;
assert(uop == _SAVE_RETURN_OFFSET);
break;
case OPARG_REPLACED:
uop = _PyUOp_Replacements[uop];
assert(uop != 0);
if (uop == _FOR_ITER_TIER_TWO) {
target += 1 + INLINE_CACHE_ENTRIES_FOR_ITER + oparg + 1 + extended;
assert(_PyCode_CODE(code)[target-1].op.code == END_FOR ||
_PyCode_CODE(code)[target-1].op.code == INSTRUMENTED_END_FOR);
}
break;
default:
fprintf(stderr,
"opcode=%d, oparg=%d; nuops=%d, i=%d; size=%d, offset=%d\n",
opcode, oparg, nuops, i,
expansion->uops[i].size,
expansion->uops[i].offset);
Py_FatalError("garbled expansion");
}
ADD_TO_TRACE(uop, oparg, operand, target);
if (uop == _POP_FRAME) {
TRACE_STACK_POP();
DPRINTF(2,
"Returning to %s (%s:%d) at byte offset %d\n",
PyUnicode_AsUTF8(code->co_qualname),
PyUnicode_AsUTF8(code->co_filename),
code->co_firstlineno,
2 * INSTR_IP(instr, code));
goto top;
}
if (uop == _PUSH_FRAME) {
assert(i + 1 == nuops);
int func_version_offset =
offsetof(_PyCallCache, func_version)/sizeof(_Py_CODEUNIT)
// Add one to account for the actual opcode/oparg pair:
+ 1;
uint32_t func_version = read_u32(&instr[func_version_offset].cache);
PyFunctionObject *func = _PyFunction_LookupByVersion(func_version);
DPRINTF(3, "Function object: %p\n", func);
if (func != NULL) {
PyCodeObject *new_code = (PyCodeObject *)PyFunction_GET_CODE(func);
if (new_code == code) {
// Recursive call, bail (we could be here forever).
DPRINTF(2, "Bailing on recursive call to %s (%s:%d)\n",
PyUnicode_AsUTF8(new_code->co_qualname),
PyUnicode_AsUTF8(new_code->co_filename),
new_code->co_firstlineno);
OPT_STAT_INC(recursive_call);
ADD_TO_TRACE(_EXIT_TRACE, 0, 0, 0);
goto done;
}
if (new_code->co_version != func_version) {
// func.__code__ was updated.
// Perhaps it may happen again, so don't bother tracing.
// TODO: Reason about this -- is it better to bail or not?
DPRINTF(2, "Bailing because co_version != func_version\n");
ADD_TO_TRACE(_EXIT_TRACE, 0, 0, 0);
goto done;
}
// Increment IP to the return address
instr += _PyOpcode_Caches[_PyOpcode_Deopt[opcode]] + 1;
TRACE_STACK_PUSH();
_Py_BloomFilter_Add(dependencies, new_code);
code = new_code;
instr = _PyCode_CODE(code);
DPRINTF(2,
"Continuing in %s (%s:%d) at byte offset %d\n",
PyUnicode_AsUTF8(code->co_qualname),
PyUnicode_AsUTF8(code->co_filename),
code->co_firstlineno,
2 * INSTR_IP(instr, code));
goto top;
}
ADD_TO_TRACE(_EXIT_TRACE, 0, 0, 0);
goto done;
}
}
break;
}
DPRINTF(2, "Unsupported opcode %s\n", _PyOpcode_OpName[opcode]);
OPT_UNSUPPORTED_OPCODE(opcode);
goto done; // Break out of loop
} // End default
} // End switch (opcode)
instr++;
// Add cache size for opcode
instr += _PyOpcode_Caches[_PyOpcode_Deopt[opcode]];
} // End for (;;)
done:
while (trace_stack_depth > 0) {
TRACE_STACK_POP();
}
assert(code == initial_code);
// Skip short traces like _SET_IP, LOAD_FAST, _SET_IP, _EXIT_TRACE
if (progress_needed || trace_length < 5) {
OPT_STAT_INC(trace_too_short);
DPRINTF(4,
"No trace for %s (%s:%d) at byte offset %d\n",
PyUnicode_AsUTF8(code->co_qualname),
PyUnicode_AsUTF8(code->co_filename),
code->co_firstlineno,
2 * INSTR_IP(initial_instr, code));
return 0;
}
ADD_TO_TRACE(_EXIT_TRACE, 0, 0, target);
DPRINTF(1,
"Created a trace for %s (%s:%d) at byte offset %d -- length %d\n",
PyUnicode_AsUTF8(code->co_qualname),
PyUnicode_AsUTF8(code->co_filename),
code->co_firstlineno,
2 * INSTR_IP(initial_instr, code),
trace_length);
OPT_HIST(trace_length + buffer_size - max_length, trace_length_hist);
return 1;
}
#undef RESERVE
#undef RESERVE_RAW
#undef INSTR_IP
#undef ADD_TO_TRACE
#undef DPRINTF
#define UNSET_BIT(array, bit) (array[(bit)>>5] &= ~(1<<((bit)&31)))
#define SET_BIT(array, bit) (array[(bit)>>5] |= (1<<((bit)&31)))
#define BIT_IS_SET(array, bit) (array[(bit)>>5] & (1<<((bit)&31)))
/* Count the number of used uops, and mark them in the bit vector `used`.
* This can be done in a single pass using simple reachability analysis,
* as there are no backward jumps.
* NOPs are excluded from the count.
*/
static int
compute_used(_PyUOpInstruction *buffer, uint32_t *used)
{
int count = 0;
SET_BIT(used, 0);
for (int i = 0; i < UOP_MAX_TRACE_LENGTH; i++) {
if (!BIT_IS_SET(used, i)) {
continue;
}
count++;
int opcode = buffer[i].opcode;
if (opcode == _JUMP_TO_TOP || opcode == _EXIT_TRACE) {
continue;
}
/* All other micro-ops fall through, so i+1 is reachable */
SET_BIT(used, i+1);
assert(opcode <= MAX_UOP_ID);
if (_PyUop_Flags[opcode] & HAS_JUMP_FLAG) {
/* Mark target as reachable */
SET_BIT(used, buffer[i].oparg);
}
if (opcode == NOP) {
count--;
UNSET_BIT(used, i);
}
}
return count;
}
/* Makes an executor from a buffer of uops.
* Account for the buffer having gaps and NOPs by computing a "used"
* bit vector and only copying the used uops. Here "used" means reachable
* and not a NOP.
*/
static _PyExecutorObject *
make_executor_from_uops(_PyUOpInstruction *buffer, _PyBloomFilter *dependencies)
{
uint32_t used[(UOP_MAX_TRACE_LENGTH + 31)/32] = { 0 };
int length = compute_used(buffer, used);
_PyExecutorObject *executor = PyObject_NewVar(_PyExecutorObject, &_PyUOpExecutor_Type, length);
if (executor == NULL) {
return NULL;
}
int dest = length - 1;
/* Scan backwards, so that we see the destinations of jumps before the jumps themselves. */
for (int i = UOP_MAX_TRACE_LENGTH-1; i >= 0; i--) {
if (!BIT_IS_SET(used, i)) {
continue;
}
executor->trace[dest] = buffer[i];
int opcode = buffer[i].opcode;
if (opcode == _POP_JUMP_IF_FALSE ||
opcode == _POP_JUMP_IF_TRUE)
{
/* The oparg of the target will already have been set to its new offset */
int oparg = executor->trace[dest].oparg;
executor->trace[dest].oparg = buffer[oparg].oparg;
}
/* Set the oparg to be the destination offset,
* so that we can set the oparg of earlier jumps correctly. */
buffer[i].oparg = dest;
dest--;
}
assert(dest == -1);
_Py_ExecutorInit(executor, dependencies);
#ifdef Py_DEBUG
char *python_lltrace = Py_GETENV("PYTHON_LLTRACE");
int lltrace = 0;
if (python_lltrace != NULL && *python_lltrace >= '0') {
lltrace = *python_lltrace - '0'; // TODO: Parse an int and all that
}
if (lltrace >= 2) {
printf("Optimized executor (length %d):\n", length);
for (int i = 0; i < length; i++) {
printf("%4d %s(%d, %d, %" PRIu64 ")\n",
i,
_PyUOpName(executor->trace[i].opcode),
executor->trace[i].oparg,
executor->trace[i].target,
executor->trace[i].operand);
}
}
#endif
return executor;
}
static int
uop_optimize(
_PyOptimizerObject *self,
PyCodeObject *code,
_Py_CODEUNIT *instr,
_PyExecutorObject **exec_ptr,
int curr_stackentries)
{
_PyBloomFilter dependencies;
_Py_BloomFilter_Init(&dependencies);
_PyUOpInstruction buffer[UOP_MAX_TRACE_LENGTH];
int err = translate_bytecode_to_trace(code, instr, buffer, UOP_MAX_TRACE_LENGTH, &dependencies);
if (err <= 0) {
// Error or nothing translated
return err;
}
OPT_STAT_INC(traces_created);
char *uop_optimize = Py_GETENV("PYTHONUOPSOPTIMIZE");
if (uop_optimize == NULL || *uop_optimize > '0') {
err = _Py_uop_analyze_and_optimize(code, buffer, UOP_MAX_TRACE_LENGTH, curr_stackentries);
if (err < 0) {
return -1;
}
}
_PyExecutorObject *executor = make_executor_from_uops(buffer, &dependencies);
if (executor == NULL) {
return -1;
}
OPT_HIST(Py_SIZE(executor), optimized_trace_length_hist);
*exec_ptr = executor;
return 1;
}
static void
uop_opt_dealloc(PyObject *self) {
PyObject_Free(self);
}
PyTypeObject _PyUOpOptimizer_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
.tp_name = "uop_optimizer",
.tp_basicsize = sizeof(_PyOptimizerObject),
.tp_itemsize = 0,
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
.tp_dealloc = uop_opt_dealloc,
};
PyObject *
PyUnstable_Optimizer_NewUOpOptimizer(void)
{
_PyOptimizerObject *opt = PyObject_New(_PyOptimizerObject, &_PyUOpOptimizer_Type);
if (opt == NULL) {
return NULL;
}
opt->optimize = uop_optimize;
opt->resume_threshold = INT16_MAX;
// Need at least 3 iterations to settle specializations.
// A few lower bits of the counter are reserved for other flags.
opt->backedge_threshold = 16 << OPTIMIZER_BITS_IN_COUNTER;
return (PyObject *)opt;
}
static void
counter_dealloc(_PyExecutorObject *self) {
PyObject *opt = (PyObject *)self->trace[0].operand;
Py_DECREF(opt);
uop_dealloc(self);
}
PyTypeObject _PyCounterExecutor_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
.tp_name = "counting_executor",
.tp_basicsize = offsetof(_PyExecutorObject, trace),
.tp_itemsize = sizeof(_PyUOpInstruction),
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
.tp_dealloc = (destructor)counter_dealloc,
.tp_methods = executor_methods,
};
static int
counter_optimize(
_PyOptimizerObject* self,
PyCodeObject *code,
_Py_CODEUNIT *instr,
_PyExecutorObject **exec_ptr,
int Py_UNUSED(curr_stackentries)
)
{
int oparg = instr->op.arg;
while (instr->op.code == EXTENDED_ARG) {
instr++;
oparg = (oparg << 8) | instr->op.arg;
}
if (instr->op.code != JUMP_BACKWARD) {
/* Counter optimizer can only handle backward edges */
return 0;
}
_Py_CODEUNIT *target = instr + 1 + _PyOpcode_Caches[JUMP_BACKWARD] - oparg;
_PyUOpInstruction buffer[3] = {
{ .opcode = _LOAD_CONST_INLINE_BORROW, .operand = (uintptr_t)self },
{ .opcode = _INTERNAL_INCREMENT_OPT_COUNTER },
{ .opcode = _EXIT_TRACE, .target = (uint32_t)(target - _PyCode_CODE(code)) }
};
_PyBloomFilter empty;
_Py_BloomFilter_Init(&empty);
_PyExecutorObject *executor = make_executor_from_uops(buffer, &empty);
if (executor == NULL) {
return -1;
}
Py_INCREF(self);
Py_SET_TYPE(executor, &_PyCounterExecutor_Type);
*exec_ptr = executor;
return 1;
}
static PyObject *
counter_get_counter(PyObject *self, PyObject *args)
{
return PyLong_FromLongLong(((_PyCounterOptimizerObject *)self)->count);
}
static PyMethodDef counter_optimizer_methods[] = {
{ "get_count", counter_get_counter, METH_NOARGS, NULL },
{ NULL, NULL },
};
PyTypeObject _PyCounterOptimizer_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
.tp_name = "Counter optimizer",
.tp_basicsize = sizeof(_PyCounterOptimizerObject),
.tp_itemsize = 0,
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
.tp_methods = counter_optimizer_methods,
.tp_dealloc = (destructor)PyObject_Del,
};
PyObject *
PyUnstable_Optimizer_NewCounter(void)
{
_PyCounterOptimizerObject *opt = (_PyCounterOptimizerObject *)_PyObject_New(&_PyCounterOptimizer_Type);
if (opt == NULL) {
return NULL;
}
opt->base.optimize = counter_optimize;
opt->base.resume_threshold = INT16_MAX;
opt->base.backedge_threshold = 0;
opt->count = 0;
return (PyObject *)opt;
}
/*****************************************
* Executor management
****************************************/
/* We use a bloomfilter with k = 6, m = 256
* The choice of k and the following constants
* could do with a more rigourous analysis,
* but here is a simple analysis:
*
* We want to keep the false positive rate low.
* For n = 5 (a trace depends on 5 objects),
* we expect 30 bits set, giving a false positive
* rate of (30/256)**6 == 2.5e-6 which is plenty
* good enough.
*
* However with n = 10 we expect 60 bits set (worst case),
* giving a false positive of (60/256)**6 == 0.0001
*
* We choose k = 6, rather than a higher number as
* it means the false positive rate grows slower for high n.
*
* n = 5, k = 6 => fp = 2.6e-6
* n = 5, k = 8 => fp = 3.5e-7
* n = 10, k = 6 => fp = 1.6e-4
* n = 10, k = 8 => fp = 0.9e-4
* n = 15, k = 6 => fp = 0.18%
* n = 15, k = 8 => fp = 0.23%
* n = 20, k = 6 => fp = 1.1%
* n = 20, k = 8 => fp = 2.3%
*
* The above analysis assumes perfect hash functions,
* but those don't exist, so the real false positive
* rates may be worse.
*/
#define K 6
#define SEED 20221211
/* TO DO -- Use more modern hash functions with better distribution of bits */
static uint64_t
address_to_hash(void *ptr) {
assert(ptr != NULL);
uint64_t uhash = SEED;
uintptr_t addr = (uintptr_t)ptr;
for (int i = 0; i < SIZEOF_VOID_P; i++) {
uhash ^= addr & 255;
uhash *= (uint64_t)_PyHASH_MULTIPLIER;
addr >>= 8;
}
return uhash;
}
void
_Py_BloomFilter_Init(_PyBloomFilter *bloom)
{
for (int i = 0; i < BLOOM_FILTER_WORDS; i++) {
bloom->bits[i] = 0;
}
}
/* We want K hash functions that each set 1 bit.
* A hash function that sets 1 bit in M bits can be trivially
* derived from a log2(M) bit hash function.
* So we extract 8 (log2(256)) bits at a time from
* the 64bit hash. */
void
_Py_BloomFilter_Add(_PyBloomFilter *bloom, void *ptr)
{
uint64_t hash = address_to_hash(ptr);
assert(K <= 8);
for (int i = 0; i < K; i++) {
uint8_t bits = hash & 255;
bloom->bits[bits >> 5] |= (1 << (bits&31));
hash >>= 8;
}
}
static bool
bloom_filter_may_contain(_PyBloomFilter *bloom, _PyBloomFilter *hashes)
{
for (int i = 0; i < BLOOM_FILTER_WORDS; i++) {
if ((bloom->bits[i] & hashes->bits[i]) != hashes->bits[i]) {
return false;
}
}
return true;
}
static void
link_executor(_PyExecutorObject *executor)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
_PyExecutorLinkListNode *links = &executor->vm_data.links;
_PyExecutorObject *head = interp->executor_list_head;
if (head == NULL) {
interp->executor_list_head = executor;
links->previous = NULL;
links->next = NULL;
}
else {
_PyExecutorObject *next = head->vm_data.links.next;
links->previous = head;
links->next = next;
if (next != NULL) {
next->vm_data.links.previous = executor;
}
head->vm_data.links.next = executor;
}
executor->vm_data.linked = true;
/* executor_list_head must be first in list */
assert(interp->executor_list_head->vm_data.links.previous == NULL);
}
static void
unlink_executor(_PyExecutorObject *executor)
{
if (!executor->vm_data.linked) {
return;
}
_PyExecutorLinkListNode *links = &executor->vm_data.links;
_PyExecutorObject *next = links->next;
_PyExecutorObject *prev = links->previous;
if (next != NULL) {
next->vm_data.links.previous = prev;
}
if (prev != NULL) {
prev->vm_data.links.next = next;
}
else {
// prev == NULL implies that executor is the list head
PyInterpreterState *interp = PyInterpreterState_Get();
assert(interp->executor_list_head == executor);
interp->executor_list_head = next;
}
executor->vm_data.linked = false;
}
/* This must be called by optimizers before using the executor */
void
_Py_ExecutorInit(_PyExecutorObject *executor, _PyBloomFilter *dependency_set)
{
executor->vm_data.valid = true;
for (int i = 0; i < BLOOM_FILTER_WORDS; i++) {
executor->vm_data.bloom.bits[i] = dependency_set->bits[i];
}
link_executor(executor);
}
/* This must be called by executors during dealloc */
void
_Py_ExecutorClear(_PyExecutorObject *executor)
{
unlink_executor(executor);
}
void
_Py_Executor_DependsOn(_PyExecutorObject *executor, void *obj)
{
assert(executor->vm_data.valid = true);
_Py_BloomFilter_Add(&executor->vm_data.bloom, obj);
}
/* Invalidate all executors that depend on `obj`
* May cause other executors to be invalidated as well
*/
void
_Py_Executors_InvalidateDependency(PyInterpreterState *interp, void *obj)
{
_PyBloomFilter obj_filter;
_Py_BloomFilter_Init(&obj_filter);
_Py_BloomFilter_Add(&obj_filter, obj);
/* Walk the list of executors */
/* TO DO -- Use a tree to avoid traversing as many objects */
for (_PyExecutorObject *exec = interp->executor_list_head; exec != NULL;) {
assert(exec->vm_data.valid);
_PyExecutorObject *next = exec->vm_data.links.next;
if (bloom_filter_may_contain(&exec->vm_data.bloom, &obj_filter)) {
exec->vm_data.valid = false;
unlink_executor(exec);
}
exec = next;
}
}
/* Invalidate all executors */
void
_Py_Executors_InvalidateAll(PyInterpreterState *interp)
{
/* Walk the list of executors */
for (_PyExecutorObject *exec = interp->executor_list_head; exec != NULL;) {
assert(exec->vm_data.valid);
_PyExecutorObject *next = exec->vm_data.links.next;
exec->vm_data.links.next = NULL;
exec->vm_data.links.previous = NULL;
exec->vm_data.valid = false;
exec->vm_data.linked = false;
exec = next;
}
interp->executor_list_head = NULL;
}
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