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GH-98831: Move assorted macros from ceval.h to a new header (#101116)
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Guido van Rossum
GitHub
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d65f485070
commit
1f0d0a432c
4 changed files with 364 additions and 385 deletions
349
Python/ceval_macros.h
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349
Python/ceval_macros.h
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// Macros needed by ceval.c and bytecodes.c
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/* Computed GOTOs, or
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the-optimization-commonly-but-improperly-known-as-"threaded code"
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using gcc's labels-as-values extension
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(http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html).
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The traditional bytecode evaluation loop uses a "switch" statement, which
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decent compilers will optimize as a single indirect branch instruction
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combined with a lookup table of jump addresses. However, since the
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indirect jump instruction is shared by all opcodes, the CPU will have a
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hard time making the right prediction for where to jump next (actually,
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it will be always wrong except in the uncommon case of a sequence of
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several identical opcodes).
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"Threaded code" in contrast, uses an explicit jump table and an explicit
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indirect jump instruction at the end of each opcode. Since the jump
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instruction is at a different address for each opcode, the CPU will make a
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separate prediction for each of these instructions, which is equivalent to
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predicting the second opcode of each opcode pair. These predictions have
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a much better chance to turn out valid, especially in small bytecode loops.
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A mispredicted branch on a modern CPU flushes the whole pipeline and
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can cost several CPU cycles (depending on the pipeline depth),
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and potentially many more instructions (depending on the pipeline width).
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A correctly predicted branch, however, is nearly free.
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At the time of this writing, the "threaded code" version is up to 15-20%
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faster than the normal "switch" version, depending on the compiler and the
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CPU architecture.
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NOTE: care must be taken that the compiler doesn't try to "optimize" the
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indirect jumps by sharing them between all opcodes. Such optimizations
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can be disabled on gcc by using the -fno-gcse flag (or possibly
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-fno-crossjumping).
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*/
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/* Use macros rather than inline functions, to make it as clear as possible
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* to the C compiler that the tracing check is a simple test then branch.
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* We want to be sure that the compiler knows this before it generates
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* the CFG.
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*/
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#ifdef WITH_DTRACE
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#define OR_DTRACE_LINE | (PyDTrace_LINE_ENABLED() ? 255 : 0)
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#else
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#define OR_DTRACE_LINE
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#endif
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#ifdef HAVE_COMPUTED_GOTOS
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#ifndef USE_COMPUTED_GOTOS
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#define USE_COMPUTED_GOTOS 1
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#endif
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#else
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#if defined(USE_COMPUTED_GOTOS) && USE_COMPUTED_GOTOS
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#error "Computed gotos are not supported on this compiler."
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#endif
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#undef USE_COMPUTED_GOTOS
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#define USE_COMPUTED_GOTOS 0
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#endif
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#ifdef Py_STATS
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#define INSTRUCTION_START(op) \
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do { \
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frame->prev_instr = next_instr++; \
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OPCODE_EXE_INC(op); \
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if (_py_stats) _py_stats->opcode_stats[lastopcode].pair_count[op]++; \
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lastopcode = op; \
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} while (0)
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#else
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#define INSTRUCTION_START(op) (frame->prev_instr = next_instr++)
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#endif
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#if USE_COMPUTED_GOTOS
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# define TARGET(op) TARGET_##op: INSTRUCTION_START(op);
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# define DISPATCH_GOTO() goto *opcode_targets[opcode]
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#else
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# define TARGET(op) case op: TARGET_##op: INSTRUCTION_START(op);
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# define DISPATCH_GOTO() goto dispatch_opcode
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#endif
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/* PRE_DISPATCH_GOTO() does lltrace if enabled. Normally a no-op */
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#ifdef LLTRACE
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#define PRE_DISPATCH_GOTO() if (lltrace) { \
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lltrace_instruction(frame, stack_pointer, next_instr); }
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#else
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#define PRE_DISPATCH_GOTO() ((void)0)
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#endif
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/* Do interpreter dispatch accounting for tracing and instrumentation */
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#define DISPATCH() \
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{ \
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NEXTOPARG(); \
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PRE_DISPATCH_GOTO(); \
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assert(cframe.use_tracing == 0 || cframe.use_tracing == 255); \
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opcode |= cframe.use_tracing OR_DTRACE_LINE; \
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DISPATCH_GOTO(); \
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}
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#define DISPATCH_SAME_OPARG() \
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{ \
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opcode = _Py_OPCODE(*next_instr); \
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PRE_DISPATCH_GOTO(); \
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opcode |= cframe.use_tracing OR_DTRACE_LINE; \
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DISPATCH_GOTO(); \
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}
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#define DISPATCH_INLINED(NEW_FRAME) \
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do { \
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_PyFrame_SetStackPointer(frame, stack_pointer); \
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frame->prev_instr = next_instr - 1; \
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(NEW_FRAME)->previous = frame; \
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frame = cframe.current_frame = (NEW_FRAME); \
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CALL_STAT_INC(inlined_py_calls); \
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goto start_frame; \
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} while (0)
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#define CHECK_EVAL_BREAKER() \
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_Py_CHECK_EMSCRIPTEN_SIGNALS_PERIODICALLY(); \
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if (_Py_atomic_load_relaxed_int32(eval_breaker)) { \
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goto handle_eval_breaker; \
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}
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/* Tuple access macros */
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#ifndef Py_DEBUG
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#define GETITEM(v, i) PyTuple_GET_ITEM((v), (i))
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#else
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static inline PyObject *
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GETITEM(PyObject *v, Py_ssize_t i) {
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assert(PyTuple_Check(v));
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assert(i >= 0);
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assert(i < PyTuple_GET_SIZE(v));
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return PyTuple_GET_ITEM(v, i);
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}
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#endif
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/* Code access macros */
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/* The integer overflow is checked by an assertion below. */
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#define INSTR_OFFSET() ((int)(next_instr - _PyCode_CODE(frame->f_code)))
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#define NEXTOPARG() do { \
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_Py_CODEUNIT word = *next_instr; \
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opcode = _Py_OPCODE(word); \
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oparg = _Py_OPARG(word); \
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} while (0)
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#define JUMPTO(x) (next_instr = _PyCode_CODE(frame->f_code) + (x))
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#define JUMPBY(x) (next_instr += (x))
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/* OpCode prediction macros
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Some opcodes tend to come in pairs thus making it possible to
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predict the second code when the first is run. For example,
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COMPARE_OP is often followed by POP_JUMP_IF_FALSE or POP_JUMP_IF_TRUE.
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Verifying the prediction costs a single high-speed test of a register
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variable against a constant. If the pairing was good, then the
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processor's own internal branch predication has a high likelihood of
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success, resulting in a nearly zero-overhead transition to the
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next opcode. A successful prediction saves a trip through the eval-loop
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including its unpredictable switch-case branch. Combined with the
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processor's internal branch prediction, a successful PREDICT has the
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effect of making the two opcodes run as if they were a single new opcode
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with the bodies combined.
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If collecting opcode statistics, your choices are to either keep the
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predictions turned-on and interpret the results as if some opcodes
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had been combined or turn-off predictions so that the opcode frequency
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counter updates for both opcodes.
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Opcode prediction is disabled with threaded code, since the latter allows
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the CPU to record separate branch prediction information for each
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opcode.
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*/
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#define PREDICT_ID(op) PRED_##op
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#if USE_COMPUTED_GOTOS
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#define PREDICT(op) if (0) goto PREDICT_ID(op)
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#else
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#define PREDICT(op) \
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do { \
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_Py_CODEUNIT word = *next_instr; \
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opcode = _Py_OPCODE(word) | cframe.use_tracing OR_DTRACE_LINE; \
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if (opcode == op) { \
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oparg = _Py_OPARG(word); \
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INSTRUCTION_START(op); \
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goto PREDICT_ID(op); \
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} \
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} while(0)
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#endif
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#define PREDICTED(op) PREDICT_ID(op):
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/* Stack manipulation macros */
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/* The stack can grow at most MAXINT deep, as co_nlocals and
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co_stacksize are ints. */
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#define STACK_LEVEL() ((int)(stack_pointer - _PyFrame_Stackbase(frame)))
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#define STACK_SIZE() (frame->f_code->co_stacksize)
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#define EMPTY() (STACK_LEVEL() == 0)
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#define TOP() (stack_pointer[-1])
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#define SECOND() (stack_pointer[-2])
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#define THIRD() (stack_pointer[-3])
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#define FOURTH() (stack_pointer[-4])
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#define PEEK(n) (stack_pointer[-(n)])
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#define POKE(n, v) (stack_pointer[-(n)] = (v))
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#define SET_TOP(v) (stack_pointer[-1] = (v))
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#define SET_SECOND(v) (stack_pointer[-2] = (v))
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#define BASIC_STACKADJ(n) (stack_pointer += n)
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#define BASIC_PUSH(v) (*stack_pointer++ = (v))
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#define BASIC_POP() (*--stack_pointer)
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#ifdef Py_DEBUG
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#define PUSH(v) do { \
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BASIC_PUSH(v); \
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assert(STACK_LEVEL() <= STACK_SIZE()); \
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} while (0)
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#define POP() (assert(STACK_LEVEL() > 0), BASIC_POP())
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#define STACK_GROW(n) do { \
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assert(n >= 0); \
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BASIC_STACKADJ(n); \
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assert(STACK_LEVEL() <= STACK_SIZE()); \
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} while (0)
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#define STACK_SHRINK(n) do { \
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assert(n >= 0); \
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assert(STACK_LEVEL() >= n); \
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BASIC_STACKADJ(-(n)); \
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} while (0)
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#else
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#define PUSH(v) BASIC_PUSH(v)
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#define POP() BASIC_POP()
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#define STACK_GROW(n) BASIC_STACKADJ(n)
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#define STACK_SHRINK(n) BASIC_STACKADJ(-(n))
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#endif
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/* Local variable macros */
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#define GETLOCAL(i) (frame->localsplus[i])
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/* The SETLOCAL() macro must not DECREF the local variable in-place and
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then store the new value; it must copy the old value to a temporary
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value, then store the new value, and then DECREF the temporary value.
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This is because it is possible that during the DECREF the frame is
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accessed by other code (e.g. a __del__ method or gc.collect()) and the
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variable would be pointing to already-freed memory. */
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#define SETLOCAL(i, value) do { PyObject *tmp = GETLOCAL(i); \
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GETLOCAL(i) = value; \
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Py_XDECREF(tmp); } while (0)
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#define GO_TO_INSTRUCTION(op) goto PREDICT_ID(op)
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#ifdef Py_STATS
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#define UPDATE_MISS_STATS(INSTNAME) \
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do { \
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STAT_INC(opcode, miss); \
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STAT_INC((INSTNAME), miss); \
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/* The counter is always the first cache entry: */ \
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if (ADAPTIVE_COUNTER_IS_ZERO(next_instr->cache)) { \
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STAT_INC((INSTNAME), deopt); \
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} \
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else { \
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/* This is about to be (incorrectly) incremented: */ \
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STAT_DEC((INSTNAME), deferred); \
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} \
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} while (0)
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#else
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#define UPDATE_MISS_STATS(INSTNAME) ((void)0)
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#endif
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#define DEOPT_IF(COND, INSTNAME) \
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if ((COND)) { \
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/* This is only a single jump on release builds! */ \
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UPDATE_MISS_STATS((INSTNAME)); \
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assert(_PyOpcode_Deopt[opcode] == (INSTNAME)); \
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GO_TO_INSTRUCTION(INSTNAME); \
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}
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#define GLOBALS() frame->f_globals
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#define BUILTINS() frame->f_builtins
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#define LOCALS() frame->f_locals
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/* Shared opcode macros */
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#define TRACE_FUNCTION_EXIT() \
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if (cframe.use_tracing) { \
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if (trace_function_exit(tstate, frame, retval)) { \
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Py_DECREF(retval); \
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goto exit_unwind; \
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} \
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}
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#define DTRACE_FUNCTION_EXIT() \
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if (PyDTrace_FUNCTION_RETURN_ENABLED()) { \
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dtrace_function_return(frame); \
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}
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#define TRACE_FUNCTION_UNWIND() \
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if (cframe.use_tracing) { \
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/* Since we are already unwinding, \
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* we don't care if this raises */ \
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trace_function_exit(tstate, frame, NULL); \
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}
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#define TRACE_FUNCTION_ENTRY() \
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if (cframe.use_tracing) { \
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_PyFrame_SetStackPointer(frame, stack_pointer); \
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int err = trace_function_entry(tstate, frame); \
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stack_pointer = _PyFrame_GetStackPointer(frame); \
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if (err) { \
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goto error; \
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} \
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}
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#define TRACE_FUNCTION_THROW_ENTRY() \
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if (cframe.use_tracing) { \
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assert(frame->stacktop >= 0); \
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if (trace_function_entry(tstate, frame)) { \
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goto exit_unwind; \
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} \
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}
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#define DTRACE_FUNCTION_ENTRY() \
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if (PyDTrace_FUNCTION_ENTRY_ENABLED()) { \
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dtrace_function_entry(frame); \
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}
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#define ADAPTIVE_COUNTER_IS_ZERO(COUNTER) \
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(((COUNTER) >> ADAPTIVE_BACKOFF_BITS) == 0)
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#define ADAPTIVE_COUNTER_IS_MAX(COUNTER) \
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(((COUNTER) >> ADAPTIVE_BACKOFF_BITS) == ((1 << MAX_BACKOFF_VALUE) - 1))
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#define DECREMENT_ADAPTIVE_COUNTER(COUNTER) \
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do { \
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assert(!ADAPTIVE_COUNTER_IS_ZERO((COUNTER))); \
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(COUNTER) -= (1 << ADAPTIVE_BACKOFF_BITS); \
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} while (0);
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#define INCREMENT_ADAPTIVE_COUNTER(COUNTER) \
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do { \
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assert(!ADAPTIVE_COUNTER_IS_MAX((COUNTER))); \
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(COUNTER) += (1 << ADAPTIVE_BACKOFF_BITS); \
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} while (0);
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#define NAME_ERROR_MSG "name '%.200s' is not defined"
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