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/* Execute compiled code */
/* XXX TO DO:
XXX speed up searching for keywords by using a dictionary
XXX document it!
*/
/* enable more aggressive intra-module optimizations, where available */
#define PY_LOCAL_AGGRESSIVE
#include "Python.h"
#include "code.h"
#include "frameobject.h"
#include "opcode.h"
#include "structmember.h"
#include <ctype.h>
#ifndef WITH_TSC
#define READ_TIMESTAMP(var)
#else
typedef unsigned long long uint64;
/* PowerPC support.
"__ppc__" appears to be the preprocessor definition to detect on OS X, whereas
"__powerpc__" appears to be the correct one for Linux with GCC
*/
#if defined(__ppc__) || defined (__powerpc__)
#define READ_TIMESTAMP(var) ppc_getcounter(&var)
static void
ppc_getcounter(uint64 *v)
{
register unsigned long tbu, tb, tbu2;
loop:
asm volatile ("mftbu %0" : "=r" (tbu) );
asm volatile ("mftb %0" : "=r" (tb) );
asm volatile ("mftbu %0" : "=r" (tbu2));
if (__builtin_expect(tbu != tbu2, 0)) goto loop;
/* The slightly peculiar way of writing the next lines is
compiled better by GCC than any other way I tried. */
((long*)(v))[0] = tbu;
((long*)(v))[1] = tb;
}
#elif defined(__i386__)
/* this is for linux/x86 (and probably any other GCC/x86 combo) */
#define READ_TIMESTAMP(val) \
__asm__ __volatile__("rdtsc" : "=A" (val))
#elif defined(__x86_64__)
/* for gcc/x86_64, the "A" constraint in DI mode means *either* rax *or* rdx;
not edx:eax as it does for i386. Since rdtsc puts its result in edx:eax
even in 64-bit mode, we need to use "a" and "d" for the lower and upper
32-bit pieces of the result. */
#define READ_TIMESTAMP(val) \
__asm__ __volatile__("rdtsc" : \
"=a" (((int*)&(val))[0]), "=d" (((int*)&(val))[1]));
#else
#error "Don't know how to implement timestamp counter for this architecture"
#endif
void dump_tsc(int opcode, int ticked, uint64 inst0, uint64 inst1,
uint64 loop0, uint64 loop1, uint64 intr0, uint64 intr1)
{
uint64 intr, inst, loop;
PyThreadState *tstate = PyThreadState_Get();
if (!tstate->interp->tscdump)
return;
intr = intr1 - intr0;
inst = inst1 - inst0 - intr;
loop = loop1 - loop0 - intr;
fprintf(stderr, "opcode=%03d t=%d inst=%06lld loop=%06lld\n",
opcode, ticked, inst, loop);
}
#endif
/* Turn this on if your compiler chokes on the big switch: */
/* #define CASE_TOO_BIG 1 */
#ifdef Py_DEBUG
/* For debugging the interpreter: */
#define LLTRACE 1 /* Low-level trace feature */
#define CHECKEXC 1 /* Double-check exception checking */
#endif
typedef PyObject *(*callproc)(PyObject *, PyObject *, PyObject *);
/* Forward declarations */
#ifdef WITH_TSC
static PyObject * call_function(PyObject ***, int, uint64*, uint64*);
#else
static PyObject * call_function(PyObject ***, int);
#endif
static PyObject * fast_function(PyObject *, PyObject ***, int, int, int);
static PyObject * do_call(PyObject *, PyObject ***, int, int);
static PyObject * ext_do_call(PyObject *, PyObject ***, int, int, int);
static PyObject * update_keyword_args(PyObject *, int, PyObject ***,
PyObject *);
static PyObject * update_star_args(int, int, PyObject *, PyObject ***);
static PyObject * load_args(PyObject ***, int);
#define CALL_FLAG_VAR 1
#define CALL_FLAG_KW 2
#ifdef LLTRACE
static int lltrace;
static int prtrace(PyObject *, char *);
#endif
static int call_trace(Py_tracefunc, PyObject *, PyFrameObject *,
int, PyObject *);
static int call_trace_protected(Py_tracefunc, PyObject *,
PyFrameObject *, int, PyObject *);
static void call_exc_trace(Py_tracefunc, PyObject *, PyFrameObject *);
static int maybe_call_line_trace(Py_tracefunc, PyObject *,
PyFrameObject *, int *, int *, int *);
static PyObject * cmp_outcome(int, PyObject *, PyObject *);
static PyObject * import_from(PyObject *, PyObject *);
static int import_all_from(PyObject *, PyObject *);
static void format_exc_check_arg(PyObject *, const char *, PyObject *);
static void format_exc_unbound(PyCodeObject *co, int oparg);
static PyObject * unicode_concatenate(PyObject *, PyObject *,
PyFrameObject *, unsigned char *);
static PyObject * special_lookup(PyObject *, _Py_Identifier *);
#define NAME_ERROR_MSG \
"name '%.200s' is not defined"
#define GLOBAL_NAME_ERROR_MSG \
"global name '%.200s' is not defined"
#define UNBOUNDLOCAL_ERROR_MSG \
"local variable '%.200s' referenced before assignment"
#define UNBOUNDFREE_ERROR_MSG \
"free variable '%.200s' referenced before assignment" \
" in enclosing scope"
/* Dynamic execution profile */
#ifdef DYNAMIC_EXECUTION_PROFILE
#ifdef DXPAIRS
static long dxpairs[257][256];
#define dxp dxpairs[256]
#else
static long dxp[256];
#endif
#endif
/* Function call profile */
#ifdef CALL_PROFILE
#define PCALL_NUM 11
static int pcall[PCALL_NUM];
#define PCALL_ALL 0
#define PCALL_FUNCTION 1
#define PCALL_FAST_FUNCTION 2
#define PCALL_FASTER_FUNCTION 3
#define PCALL_METHOD 4
#define PCALL_BOUND_METHOD 5
#define PCALL_CFUNCTION 6
#define PCALL_TYPE 7
#define PCALL_GENERATOR 8
#define PCALL_OTHER 9
#define PCALL_POP 10
/* Notes about the statistics
PCALL_FAST stats
FAST_FUNCTION means no argument tuple needs to be created.
FASTER_FUNCTION means that the fast-path frame setup code is used.
If there is a method call where the call can be optimized by changing
the argument tuple and calling the function directly, it gets recorded
twice.
As a result, the relationship among the statistics appears to be
PCALL_ALL == PCALL_FUNCTION + PCALL_METHOD - PCALL_BOUND_METHOD +
PCALL_CFUNCTION + PCALL_TYPE + PCALL_GENERATOR + PCALL_OTHER
PCALL_FUNCTION > PCALL_FAST_FUNCTION > PCALL_FASTER_FUNCTION
PCALL_METHOD > PCALL_BOUND_METHOD
*/
#define PCALL(POS) pcall[POS]++
PyObject *
PyEval_GetCallStats(PyObject *self)
{
return Py_BuildValue("iiiiiiiiiii",
pcall[0], pcall[1], pcall[2], pcall[3],
pcall[4], pcall[5], pcall[6], pcall[7],
pcall[8], pcall[9], pcall[10]);
}
#else
#define PCALL(O)
PyObject *
PyEval_GetCallStats(PyObject *self)
{
Py_INCREF(Py_None);
return Py_None;
}
#endif
#ifdef WITH_THREAD
#define GIL_REQUEST _Py_atomic_load_relaxed(&gil_drop_request)
#else
#define GIL_REQUEST 0
#endif
/* This can set eval_breaker to 0 even though gil_drop_request became
1. We believe this is all right because the eval loop will release
the GIL eventually anyway. */
#define COMPUTE_EVAL_BREAKER() \
_Py_atomic_store_relaxed( \
&eval_breaker, \
GIL_REQUEST | \
_Py_atomic_load_relaxed(&pendingcalls_to_do) | \
pending_async_exc)
#ifdef WITH_THREAD
#define SET_GIL_DROP_REQUEST() \
do { \
_Py_atomic_store_relaxed(&gil_drop_request, 1); \
_Py_atomic_store_relaxed(&eval_breaker, 1); \
} while (0)
#define RESET_GIL_DROP_REQUEST() \
do { \
_Py_atomic_store_relaxed(&gil_drop_request, 0); \
COMPUTE_EVAL_BREAKER(); \
} while (0)
#endif
/* Pending calls are only modified under pending_lock */
#define SIGNAL_PENDING_CALLS() \
do { \
_Py_atomic_store_relaxed(&pendingcalls_to_do, 1); \
_Py_atomic_store_relaxed(&eval_breaker, 1); \
} while (0)
#define UNSIGNAL_PENDING_CALLS() \
do { \
_Py_atomic_store_relaxed(&pendingcalls_to_do, 0); \
COMPUTE_EVAL_BREAKER(); \
} while (0)
#define SIGNAL_ASYNC_EXC() \
do { \
pending_async_exc = 1; \
_Py_atomic_store_relaxed(&eval_breaker, 1); \
} while (0)
#define UNSIGNAL_ASYNC_EXC() \
do { pending_async_exc = 0; COMPUTE_EVAL_BREAKER(); } while (0)
#ifdef WITH_THREAD
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#include "pythread.h"
static PyThread_type_lock pending_lock = 0; /* for pending calls */
static long main_thread = 0;
/* This single variable consolidates all requests to break out of the fast path
in the eval loop. */
static _Py_atomic_int eval_breaker = {0};
/* Request for dropping the GIL */
static _Py_atomic_int gil_drop_request = {0};
/* Request for running pending calls. */
static _Py_atomic_int pendingcalls_to_do = {0};
/* Request for looking at the `async_exc` field of the current thread state.
Guarded by the GIL. */
static int pending_async_exc = 0;
#include "ceval_gil.h"
int
PyEval_ThreadsInitialized(void)
{
return gil_created();
}
void
PyEval_InitThreads(void)
{
if (gil_created())
return;
create_gil();
take_gil(PyThreadState_GET());
main_thread = PyThread_get_thread_ident();
if (!pending_lock)
pending_lock = PyThread_allocate_lock();
}
void
_PyEval_FiniThreads(void)
{
if (!gil_created())
return;
destroy_gil();
assert(!gil_created());
}
void
PyEval_AcquireLock(void)
{
PyThreadState *tstate = PyThreadState_GET();
if (tstate == NULL)
Py_FatalError("PyEval_AcquireLock: current thread state is NULL");
take_gil(tstate);
}
void
PyEval_ReleaseLock(void)
{
/* This function must succeed when the current thread state is NULL.
We therefore avoid PyThreadState_GET() which dumps a fatal error
in debug mode.
*/
drop_gil((PyThreadState*)_Py_atomic_load_relaxed(
&_PyThreadState_Current));
}
void
PyEval_AcquireThread(PyThreadState *tstate)
{
if (tstate == NULL)
Py_FatalError("PyEval_AcquireThread: NULL new thread state");
/* Check someone has called PyEval_InitThreads() to create the lock */
assert(gil_created());
take_gil(tstate);
if (PyThreadState_Swap(tstate) != NULL)
Py_FatalError(
"PyEval_AcquireThread: non-NULL old thread state");
}
void
PyEval_ReleaseThread(PyThreadState *tstate)
{
if (tstate == NULL)
Py_FatalError("PyEval_ReleaseThread: NULL thread state");
if (PyThreadState_Swap(NULL) != tstate)
Py_FatalError("PyEval_ReleaseThread: wrong thread state");
drop_gil(tstate);
}
/* This function is called from PyOS_AfterFork to ensure that newly
created child processes don't hold locks referring to threads which
are not running in the child process. (This could also be done using
pthread_atfork mechanism, at least for the pthreads implementation.) */
void
PyEval_ReInitThreads(void)
{
_Py_IDENTIFIER(_after_fork);
PyObject *threading, *result;
PyThreadState *tstate = PyThreadState_GET();
if (!gil_created())
return;
recreate_gil();
pending_lock = PyThread_allocate_lock();
take_gil(tstate);
main_thread = PyThread_get_thread_ident();
/* Update the threading module with the new state.
*/
tstate = PyThreadState_GET();
threading = PyMapping_GetItemString(tstate->interp->modules,
"threading");
if (threading == NULL) {
/* threading not imported */
PyErr_Clear();
return;
}
result = _PyObject_CallMethodId(threading, &PyId__after_fork, NULL);
if (result == NULL)
PyErr_WriteUnraisable(threading);
else
Py_DECREF(result);
Py_DECREF(threading);
}
#else
static _Py_atomic_int eval_breaker = {0};
static int pending_async_exc = 0;
#endif /* WITH_THREAD */
/* This function is used to signal that async exceptions are waiting to be
raised, therefore it is also useful in non-threaded builds. */
void
_PyEval_SignalAsyncExc(void)
{
SIGNAL_ASYNC_EXC();
}
/* Functions save_thread and restore_thread are always defined so
dynamically loaded modules needn't be compiled separately for use
with and without threads: */
PyThreadState *
PyEval_SaveThread(void)
{
PyThreadState *tstate = PyThreadState_Swap(NULL);
if (tstate == NULL)
Py_FatalError("PyEval_SaveThread: NULL tstate");
#ifdef WITH_THREAD
if (gil_created())
drop_gil(tstate);
#endif
return tstate;
}
void
PyEval_RestoreThread(PyThreadState *tstate)
{
if (tstate == NULL)
Py_FatalError("PyEval_RestoreThread: NULL tstate");
#ifdef WITH_THREAD
if (gil_created()) {
int err = errno;
take_gil(tstate);
/* _Py_Finalizing is protected by the GIL */
if (_Py_Finalizing && tstate != _Py_Finalizing) {
drop_gil(tstate);
PyThread_exit_thread();
assert(0); /* unreachable */
}
errno = err;
}
#endif
PyThreadState_Swap(tstate);
}
/* Mechanism whereby asynchronously executing callbacks (e.g. UNIX
signal handlers or Mac I/O completion routines) can schedule calls
to a function to be called synchronously.
The synchronous function is called with one void* argument.
It should return 0 for success or -1 for failure -- failure should
be accompanied by an exception.
If registry succeeds, the registry function returns 0; if it fails
(e.g. due to too many pending calls) it returns -1 (without setting
an exception condition).
Note that because registry may occur from within signal handlers,
or other asynchronous events, calling malloc() is unsafe!
#ifdef WITH_THREAD
Any thread can schedule pending calls, but only the main thread
will execute them.
There is no facility to schedule calls to a particular thread, but
that should be easy to change, should that ever be required. In
that case, the static variables here should go into the python
threadstate.
#endif
*/
#ifdef WITH_THREAD
/* The WITH_THREAD implementation is thread-safe. It allows
scheduling to be made from any thread, and even from an executing
callback.
*/
#define NPENDINGCALLS 32
static struct {
int (*func)(void *);
void *arg;
} pendingcalls[NPENDINGCALLS];
static int pendingfirst = 0;
static int pendinglast = 0;
int
Py_AddPendingCall(int (*func)(void *), void *arg)
{
int i, j, result=0;
PyThread_type_lock lock = pending_lock;
/* try a few times for the lock. Since this mechanism is used
* for signal handling (on the main thread), there is a (slim)
* chance that a signal is delivered on the same thread while we
* hold the lock during the Py_MakePendingCalls() function.
* This avoids a deadlock in that case.
* Note that signals can be delivered on any thread. In particular,
* on Windows, a SIGINT is delivered on a system-created worker
* thread.
* We also check for lock being NULL, in the unlikely case that
* this function is called before any bytecode evaluation takes place.
*/
if (lock != NULL) {
for (i = 0; i<100; i++) {
if (PyThread_acquire_lock(lock, NOWAIT_LOCK))
break;
}
if (i == 100)
return -1;
}
i = pendinglast;
j = (i + 1) % NPENDINGCALLS;
if (j == pendingfirst) {
result = -1; /* Queue full */
} else {
pendingcalls[i].func = func;
pendingcalls[i].arg = arg;
pendinglast = j;
}
/* signal main loop */
SIGNAL_PENDING_CALLS();
if (lock != NULL)
PyThread_release_lock(lock);
return result;
}
int
Py_MakePendingCalls(void)
{
static int busy = 0;
int i;
int r = 0;
if (!pending_lock) {
/* initial allocation of the lock */
pending_lock = PyThread_allocate_lock();
if (pending_lock == NULL)
return -1;
}
/* only service pending calls on main thread */
if (main_thread && PyThread_get_thread_ident() != main_thread)
return 0;
/* don't perform recursive pending calls */
if (busy)
return 0;
busy = 1;
/* perform a bounded number of calls, in case of recursion */
for (i=0; i<NPENDINGCALLS; i++) {
int j;
int (*func)(void *);
void *arg = NULL;
/* pop one item off the queue while holding the lock */
PyThread_acquire_lock(pending_lock, WAIT_LOCK);
j = pendingfirst;
if (j == pendinglast) {
func = NULL; /* Queue empty */
} else {
func = pendingcalls[j].func;
arg = pendingcalls[j].arg;
pendingfirst = (j + 1) % NPENDINGCALLS;
}
if (pendingfirst != pendinglast)
SIGNAL_PENDING_CALLS();
else
UNSIGNAL_PENDING_CALLS();
PyThread_release_lock(pending_lock);
/* having released the lock, perform the callback */
if (func == NULL)
break;
r = func(arg);
if (r)
break;
}
busy = 0;
return r;
}
#else /* if ! defined WITH_THREAD */
/*
WARNING! ASYNCHRONOUSLY EXECUTING CODE!
This code is used for signal handling in python that isn't built
with WITH_THREAD.
Don't use this implementation when Py_AddPendingCalls() can happen
on a different thread!
There are two possible race conditions:
(1) nested asynchronous calls to Py_AddPendingCall()
(2) AddPendingCall() calls made while pending calls are being processed.
(1) is very unlikely because typically signal delivery
is blocked during signal handling. So it should be impossible.
(2) is a real possibility.
The current code is safe against (2), but not against (1).
The safety against (2) is derived from the fact that only one
thread is present, interrupted by signals, and that the critical
section is protected with the "busy" variable. On Windows, which
delivers SIGINT on a system thread, this does not hold and therefore
Windows really shouldn't use this version.
The two threads could theoretically wiggle around the "busy" variable.
*/
#define NPENDINGCALLS 32
static struct {
int (*func)(void *);
void *arg;
} pendingcalls[NPENDINGCALLS];
static volatile int pendingfirst = 0;
static volatile int pendinglast = 0;
static _Py_atomic_int pendingcalls_to_do = {0};
int
Py_AddPendingCall(int (*func)(void *), void *arg)
{
static volatile int busy = 0;
int i, j;
/* XXX Begin critical section */
if (busy)
return -1;
busy = 1;
i = pendinglast;
j = (i + 1) % NPENDINGCALLS;
if (j == pendingfirst) {
busy = 0;
return -1; /* Queue full */
}
pendingcalls[i].func = func;
pendingcalls[i].arg = arg;
pendinglast = j;
SIGNAL_PENDING_CALLS();
busy = 0;
/* XXX End critical section */
return 0;
}
int
Py_MakePendingCalls(void)
{
static int busy = 0;
if (busy)
return 0;
busy = 1;
UNSIGNAL_PENDING_CALLS();
for (;;) {
int i;
int (*func)(void *);
void *arg;
i = pendingfirst;
if (i == pendinglast)
break; /* Queue empty */
func = pendingcalls[i].func;
arg = pendingcalls[i].arg;
pendingfirst = (i + 1) % NPENDINGCALLS;
if (func(arg) < 0) {
busy = 0;
SIGNAL_PENDING_CALLS(); /* We're not done yet */
return -1;
}
}
busy = 0;
return 0;
}
#endif /* WITH_THREAD */
/* The interpreter's recursion limit */
#ifndef Py_DEFAULT_RECURSION_LIMIT
#define Py_DEFAULT_RECURSION_LIMIT 1000
#endif
static int recursion_limit = Py_DEFAULT_RECURSION_LIMIT;
int _Py_CheckRecursionLimit = Py_DEFAULT_RECURSION_LIMIT;
int
Py_GetRecursionLimit(void)
{
return recursion_limit;
}
void
Py_SetRecursionLimit(int new_limit)
{
recursion_limit = new_limit;
_Py_CheckRecursionLimit = recursion_limit;
}
/* the macro Py_EnterRecursiveCall() only calls _Py_CheckRecursiveCall()
if the recursion_depth reaches _Py_CheckRecursionLimit.
If USE_STACKCHECK, the macro decrements _Py_CheckRecursionLimit
to guarantee that _Py_CheckRecursiveCall() is regularly called.
Without USE_STACKCHECK, there is no need for this. */
int
_Py_CheckRecursiveCall(char *where)
{
PyThreadState *tstate = PyThreadState_GET();
#ifdef USE_STACKCHECK
if (PyOS_CheckStack()) {
--tstate->recursion_depth;
PyErr_SetString(PyExc_MemoryError, "Stack overflow");
return -1;
}
#endif
_Py_CheckRecursionLimit = recursion_limit;
if (tstate->recursion_critical)
/* Somebody asked that we don't check for recursion. */
return 0;
if (tstate->overflowed) {
if (tstate->recursion_depth > recursion_limit + 50) {
/* Overflowing while handling an overflow. Give up. */
Py_FatalError("Cannot recover from stack overflow.");
}
return 0;
}
if (tstate->recursion_depth > recursion_limit) {
--tstate->recursion_depth;
tstate->overflowed = 1;
PyErr_Format(PyExc_RuntimeError,
"maximum recursion depth exceeded%s",
where);
return -1;
}
return 0;
}
/* Status code for main loop (reason for stack unwind) */
enum why_code {
WHY_NOT = 0x0001, /* No error */
WHY_EXCEPTION = 0x0002, /* Exception occurred */
WHY_RERAISE = 0x0004, /* Exception re-raised by 'finally' */
WHY_RETURN = 0x0008, /* 'return' statement */
WHY_BREAK = 0x0010, /* 'break' statement */
WHY_CONTINUE = 0x0020, /* 'continue' statement */
WHY_YIELD = 0x0040, /* 'yield' operator */
WHY_SILENCED = 0x0080 /* Exception silenced by 'with' */
};
static void save_exc_state(PyThreadState *, PyFrameObject *);
static void swap_exc_state(PyThreadState *, PyFrameObject *);
static void restore_and_clear_exc_state(PyThreadState *, PyFrameObject *);
static enum why_code do_raise(PyObject *, PyObject *);
static int unpack_iterable(PyObject *, int, int, PyObject **);
/* Records whether tracing is on for any thread. Counts the number of
threads for which tstate->c_tracefunc is non-NULL, so if the value
is 0, we know we don't have to check this thread's c_tracefunc.
This speeds up the if statement in PyEval_EvalFrameEx() after
fast_next_opcode*/
static int _Py_TracingPossible = 0;
PyObject *
PyEval_EvalCode(PyObject *co, PyObject *globals, PyObject *locals)
{
return PyEval_EvalCodeEx(co,
globals, locals,
(PyObject **)NULL, 0,
(PyObject **)NULL, 0,
(PyObject **)NULL, 0,
NULL, NULL);
}
/* Interpreter main loop */
PyObject *
PyEval_EvalFrame(PyFrameObject *f) {
/* This is for backward compatibility with extension modules that
used this API; core interpreter code should call
PyEval_EvalFrameEx() */
return PyEval_EvalFrameEx(f, 0);
}
PyObject *
PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
{
#ifdef DXPAIRS
int lastopcode = 0;
#endif
register PyObject **stack_pointer; /* Next free slot in value stack */
register unsigned char *next_instr;
register int opcode; /* Current opcode */
register int oparg; /* Current opcode argument, if any */
register enum why_code why; /* Reason for block stack unwind */
register int err; /* Error status -- nonzero if error */
register PyObject *x; /* Result object -- NULL if error */
register PyObject *v; /* Temporary objects popped off stack */
register PyObject *w;
register PyObject *u;
register PyObject *t;
register PyObject **fastlocals, **freevars;
PyObject *retval = NULL; /* Return value */
PyThreadState *tstate = PyThreadState_GET();
PyCodeObject *co;
/* when tracing we set things up so that
not (instr_lb <= current_bytecode_offset < instr_ub)
is true when the line being executed has changed. The
initial values are such as to make this false the first
time it is tested. */
int instr_ub = -1, instr_lb = 0, instr_prev = -1;
unsigned char *first_instr;
PyObject *names;
PyObject *consts;
#ifdef LLTRACE
_Py_IDENTIFIER(__ltrace__);
#endif
/* Computed GOTOs, or
the-optimization-commonly-but-improperly-known-as-"threaded code"
using gcc's labels-as-values extension
(http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html).
The traditional bytecode evaluation loop uses a "switch" statement, which
decent compilers will optimize as a single indirect branch instruction
combined with a lookup table of jump addresses. However, since the
indirect jump instruction is shared by all opcodes, the CPU will have a
hard time making the right prediction for where to jump next (actually,
it will be always wrong except in the uncommon case of a sequence of
several identical opcodes).
"Threaded code" in contrast, uses an explicit jump table and an explicit
indirect jump instruction at the end of each opcode. Since the jump
instruction is at a different address for each opcode, the CPU will make a
separate prediction for each of these instructions, which is equivalent to
predicting the second opcode of each opcode pair. These predictions have
a much better chance to turn out valid, especially in small bytecode loops.
A mispredicted branch on a modern CPU flushes the whole pipeline and
can cost several CPU cycles (depending on the pipeline depth),
and potentially many more instructions (depending on the pipeline width).
A correctly predicted branch, however, is nearly free.
At the time of this writing, the "threaded code" version is up to 15-20%
faster than the normal "switch" version, depending on the compiler and the
CPU architecture.
We disable the optimization if DYNAMIC_EXECUTION_PROFILE is defined,
because it would render the measurements invalid.
NOTE: care must be taken that the compiler doesn't try to "optimize" the
indirect jumps by sharing them between all opcodes. Such optimizations
can be disabled on gcc by using the -fno-gcse flag (or possibly
-fno-crossjumping).
*/
#ifdef DYNAMIC_EXECUTION_PROFILE
#undef USE_COMPUTED_GOTOS
#define USE_COMPUTED_GOTOS 0
#endif
#ifdef HAVE_COMPUTED_GOTOS
#ifndef USE_COMPUTED_GOTOS
#define USE_COMPUTED_GOTOS 1
#endif
#else
#if defined(USE_COMPUTED_GOTOS) && USE_COMPUTED_GOTOS
#error "Computed gotos are not supported on this compiler."
#endif
#undef USE_COMPUTED_GOTOS
#define USE_COMPUTED_GOTOS 0
#endif
#if USE_COMPUTED_GOTOS
/* Import the static jump table */
#include "opcode_targets.h"
/* This macro is used when several opcodes defer to the same implementation
(e.g. SETUP_LOOP, SETUP_FINALLY) */
#define TARGET_WITH_IMPL(op, impl) \
TARGET_##op: \
opcode = op; \
if (HAS_ARG(op)) \
oparg = NEXTARG(); \
case op: \
goto impl; \
#define TARGET(op) \
TARGET_##op: \
opcode = op; \
if (HAS_ARG(op)) \
oparg = NEXTARG(); \
case op:
#define DISPATCH() \
{ \
if (!_Py_atomic_load_relaxed(&eval_breaker)) { \
FAST_DISPATCH(); \
} \
continue; \
}
#ifdef LLTRACE
#define FAST_DISPATCH() \
{ \
if (!lltrace && !_Py_TracingPossible) { \
f->f_lasti = INSTR_OFFSET(); \
goto *opcode_targets[*next_instr++]; \
} \
goto fast_next_opcode; \
}
#else
#define FAST_DISPATCH() \
{ \
if (!_Py_TracingPossible) { \
f->f_lasti = INSTR_OFFSET(); \
goto *opcode_targets[*next_instr++]; \
} \
goto fast_next_opcode; \
}
#endif
#else
#define TARGET(op) \
case op:
#define TARGET_WITH_IMPL(op, impl) \
/* silence compiler warnings about `impl` unused */ \
if (0) goto impl; \
case op:
#define DISPATCH() continue
#define FAST_DISPATCH() goto fast_next_opcode
#endif
/* Tuple access macros */
#ifndef Py_DEBUG
#define GETITEM(v, i) PyTuple_GET_ITEM((PyTupleObject *)(v), (i))
#else
#define GETITEM(v, i) PyTuple_GetItem((v), (i))
#endif
#ifdef WITH_TSC
/* Use Pentium timestamp counter to mark certain events:
inst0 -- beginning of switch statement for opcode dispatch
inst1 -- end of switch statement (may be skipped)
loop0 -- the top of the mainloop
loop1 -- place where control returns again to top of mainloop
(may be skipped)
intr1 -- beginning of long interruption
intr2 -- end of long interruption
Many opcodes call out to helper C functions. In some cases, the
time in those functions should be counted towards the time for the
opcode, but not in all cases. For example, a CALL_FUNCTION opcode
calls another Python function; there's no point in charge all the
bytecode executed by the called function to the caller.
It's hard to make a useful judgement statically. In the presence
of operator overloading, it's impossible to tell if a call will
execute new Python code or not.
It's a case-by-case judgement. I'll use intr1 for the following
cases:
IMPORT_STAR
IMPORT_FROM
CALL_FUNCTION (and friends)
*/
uint64 inst0, inst1, loop0, loop1, intr0 = 0, intr1 = 0;
int ticked = 0;
READ_TIMESTAMP(inst0);
READ_TIMESTAMP(inst1);
READ_TIMESTAMP(loop0);
READ_TIMESTAMP(loop1);
/* shut up the compiler */
opcode = 0;
#endif
/* Code access macros */
#define INSTR_OFFSET() ((int)(next_instr - first_instr))
#define NEXTOP() (*next_instr++)
#define NEXTARG() (next_instr += 2, (next_instr[-1]<<8) + next_instr[-2])
#define PEEKARG() ((next_instr[2]<<8) + next_instr[1])