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gh-104584: Baby steps towards generating and executing traces (#105924)
Added a new, experimental, tracing optimizer and interpreter (a.k.a. "tier 2"). This currently pessimizes, so don't use yet -- this is infrastructure so we can experiment with optimizing passes. To enable it, pass ``-Xuops`` or set ``PYTHONUOPS=1``. To get debug output, set ``PYTHONUOPSDEBUG=N`` where ``N`` is a debug level (0-4, where 0 is no debug output and 4 is excessively verbose). All of this code is likely to change dramatically before the 3.13 feature freeze. But this is a first step.
This commit is contained in:
Guido van Rossum
GitHub
parent
d3af83b934
commit
51fc725117
21 changed files with 2559 additions and 305 deletions
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@ -3,7 +3,9 @@
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#include "opcode.h"
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#include "pycore_interp.h"
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#include "pycore_opcode.h"
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#include "opcode_metadata.h"
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#include "pycore_pystate.h"
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#include "pycore_uops.h"
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#include "cpython/optimizer.h"
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#include <stdbool.h>
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#include <stdint.h>
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@ -278,3 +280,200 @@ PyUnstable_Optimizer_NewCounter(void)
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opt->count = 0;
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return (PyObject *)opt;
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}
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///////////////////// Experimental UOp Optimizer /////////////////////
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#ifdef Py_DEBUG
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/* For debugging the interpreter: */
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# define LLTRACE 1 /* Low-level trace feature */
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#endif
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static void
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uop_dealloc(_PyUOpExecutorObject *self) {
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PyObject_Free(self);
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}
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static PyTypeObject UOpExecutor_Type = {
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PyVarObject_HEAD_INIT(&PyType_Type, 0)
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.tp_name = "uop_executor",
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.tp_basicsize = sizeof(_PyUOpExecutorObject),
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.tp_itemsize = 0,
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.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
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.tp_dealloc = (destructor)uop_dealloc,
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};
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static int
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translate_bytecode_to_trace(
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PyCodeObject *code,
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_Py_CODEUNIT *instr,
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_PyUOpInstruction *trace,
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int max_length)
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{
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#ifdef LLTRACE
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char *uop_debug = Py_GETENV("PYTHONUOPSDEBUG");
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int lltrace = 0;
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if (uop_debug != NULL && *uop_debug >= '0') {
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lltrace = *uop_debug - '0'; // TODO: Parse an int and all that
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}
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if (lltrace >= 4) {
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fprintf(stderr,
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"Optimizing %s (%s:%d) at offset %ld\n",
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PyUnicode_AsUTF8(code->co_qualname),
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PyUnicode_AsUTF8(code->co_filename),
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code->co_firstlineno,
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(long)(instr - (_Py_CODEUNIT *)code->co_code_adaptive));
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}
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#define ADD_TO_TRACE(OPCODE, OPERAND) \
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if (lltrace >= 2) { \
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const char *opname = (OPCODE) < 256 ? _PyOpcode_OpName[(OPCODE)] : ""; \
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fprintf(stderr, " ADD_TO_TRACE(%s %d, %" PRIu64 ")\n", opname, (OPCODE), (uint64_t)(OPERAND)); \
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} \
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trace[trace_length].opcode = (OPCODE); \
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trace[trace_length].operand = (OPERAND); \
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trace_length++;
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#else
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#define ADD_TO_TRACE(OPCODE, OPERAND) \
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trace[trace_length].opcode = (OPCODE); \
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trace[trace_length].operand = (OPERAND); \
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trace_length++;
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#endif
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int trace_length = 0;
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// Always reserve space for one uop, plus SET_UP, plus EXIT_TRACE
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while (trace_length + 3 <= max_length) {
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int opcode = instr->op.code;
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uint64_t operand = instr->op.arg;
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switch (opcode) {
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case LOAD_FAST_LOAD_FAST:
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{
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// Reserve space for two uops (+ SETUP + EXIT_TRACE)
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if (trace_length + 4 > max_length) {
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goto done;
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}
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uint64_t oparg1 = operand >> 4;
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uint64_t oparg2 = operand & 15;
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ADD_TO_TRACE(LOAD_FAST, oparg1);
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ADD_TO_TRACE(LOAD_FAST, oparg2);
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break;
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}
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default:
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{
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const struct opcode_macro_expansion *expansion = &_PyOpcode_macro_expansion[opcode];
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if (expansion->nuops > 0) {
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// Reserve space for nuops (+ SETUP + EXIT_TRACE)
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int nuops = expansion->nuops;
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if (trace_length + nuops + 2 > max_length) {
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goto done;
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}
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for (int i = 0; i < nuops; i++) {
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int offset = expansion->uops[i].offset;
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switch (expansion->uops[i].size) {
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case 0:
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break;
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case 1:
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operand = read_u16(&instr[offset].cache);
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break;
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case 2:
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operand = read_u32(&instr[offset].cache);
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break;
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case 4:
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operand = read_u64(&instr[offset].cache);
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break;
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default:
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fprintf(stderr,
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"opcode=%d, operand=%" PRIu64 "; nuops=%d, i=%d; size=%d, offset=%d\n",
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opcode, operand, nuops, i,
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expansion->uops[i].size,
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expansion->uops[i].offset);
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Py_FatalError("garbled expansion");
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}
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ADD_TO_TRACE(expansion->uops[i].uop, operand);
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assert(expansion->uops[0].size == 0); // TODO
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}
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break;
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}
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// fprintf(stderr, "Unsupported opcode %d\n", opcode);
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goto done; // Break out of while loop
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}
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}
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instr++;
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// Add cache size for opcode
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instr += _PyOpcode_Caches[_PyOpcode_Deopt[opcode]];
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ADD_TO_TRACE(SET_IP, (int)(instr - (_Py_CODEUNIT *)code->co_code_adaptive));
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}
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done:
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if (trace_length > 0) {
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ADD_TO_TRACE(EXIT_TRACE, 0);
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#ifdef LLTRACE
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if (lltrace >= 1) {
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fprintf(stderr,
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"Created a trace for %s (%s:%d) at offset %ld -- length %d\n",
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PyUnicode_AsUTF8(code->co_qualname),
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PyUnicode_AsUTF8(code->co_filename),
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code->co_firstlineno,
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(long)(instr - (_Py_CODEUNIT *)code->co_code_adaptive),
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trace_length);
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}
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#endif
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}
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else {
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#ifdef LLTRACE
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if (lltrace >= 4) {
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fprintf(stderr,
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"No trace for %s (%s:%d) at offset %ld\n",
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PyUnicode_AsUTF8(code->co_qualname),
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PyUnicode_AsUTF8(code->co_filename),
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code->co_firstlineno,
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(long)(instr - (_Py_CODEUNIT *)code->co_code_adaptive));
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}
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#endif
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}
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return trace_length;
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#undef ADD_TO_TRACE
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}
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static int
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uop_optimize(
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_PyOptimizerObject *self,
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PyCodeObject *code,
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_Py_CODEUNIT *instr,
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_PyExecutorObject **exec_ptr)
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{
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_PyUOpInstruction trace[_Py_UOP_MAX_TRACE_LENGTH];
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int trace_length = translate_bytecode_to_trace(code, instr, trace, _Py_UOP_MAX_TRACE_LENGTH);
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if (trace_length <= 0) {
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// Error or nothing translated
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return trace_length;
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}
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OBJECT_STAT_INC(optimization_traces_created);
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_PyUOpExecutorObject *executor = (_PyUOpExecutorObject *)_PyObject_New(&UOpExecutor_Type);
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if (executor == NULL) {
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return -1;
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}
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executor->base.execute = _PyUopExecute;
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memcpy(executor->trace, trace, trace_length * sizeof(_PyUOpInstruction));
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*exec_ptr = (_PyExecutorObject *)executor;
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return 1;
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}
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static PyTypeObject UOpOptimizer_Type = {
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PyVarObject_HEAD_INIT(&PyType_Type, 0)
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.tp_name = "uop_optimizer",
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.tp_basicsize = sizeof(_PyOptimizerObject),
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.tp_itemsize = 0,
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.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
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};
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PyObject *
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PyUnstable_Optimizer_NewUOpOptimizer(void)
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{
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_PyOptimizerObject *opt = (_PyOptimizerObject *)_PyObject_New(&UOpOptimizer_Type);
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if (opt == NULL) {
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return NULL;
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}
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opt->optimize = uop_optimize;
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opt->resume_threshold = UINT16_MAX;
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opt->backedge_threshold = 0;
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return (PyObject *)opt;
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}
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