src/third_party/mozjs/js/src/vm/Probes.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef vm_Probes_h
#define vm_Probes_h

#include "jspubtd.h"
#include "jsobj.h"
#include "vm/Stack.h"

#ifdef INCLUDE_MOZILLA_DTRACE
#include "javascript-trace.h"
#endif

namespace js {

namespace Probes {

/*
 * Static probes
 *
 * The probe points defined in this file are scattered around the SpiderMonkey
 * source tree. The presence of Probes::someEvent() means that someEvent is
 * about to happen or has happened. To the extent possible, probes should be
 * inserted in all paths associated with a given event, regardless of the
 * active runmode (interpreter/traceJIT/methodJIT/ionJIT).
 *
 * When a probe fires, it is handled by any probe handling backends that have
 * been compiled in. By default, most probes do nothing or at least do nothing
 * expensive, so the presence of the probe should have negligible effect on
 * running time. (Probes in slow paths may do something by default, as long as
 * there is no noticeable slowdown.)
 *
 * For some probes, the mere existence of the probe is too expensive even if it
 * does nothing when called. For example, just having consistent information
 * available for a function call entry/exit probe causes the JITs to
 * de-optimize function calls. In those cases, the JITs may query at compile
 * time whether a probe is desired, and omit the probe invocation if not. If a
 * probe is runtime-disabled at compilation time, it is not guaranteed to fire
 * within a compiled function if it is later enabled.
 *
 * Not all backends handle all of the probes listed here.
 */

/*
 * Internal use only: remember whether "profiling", whatever that means, is
 * currently active. Used for state management.
 */
extern bool ProfilingActive;

extern const char nullName[];
extern const char anonymousName[];

/*
 * Test whether we are tracking JS function call enter/exit. The JITs use this
 * to decide whether they can optimize in a way that would prevent probes from
 * firing.
 */
bool callTrackingActive(JSContext *);

/*
 * Test whether anything is looking for JIT native code registration events.
 * This information will not be collected otherwise.
 */
bool wantNativeAddressInfo(JSContext *);

/* Entering a JS function */
bool enterScript(JSContext *, JSScript *, JSFunction *, StackFrame *);

/* About to leave a JS function */
bool exitScript(JSContext *, JSScript *, JSFunction *, AbstractFramePtr);
bool exitScript(JSContext *, JSScript *, JSFunction *, StackFrame *);

/* Executing a script */
bool startExecution(JSScript *script);

/* Script has completed execution */
bool stopExecution(JSScript *script);

/*
 * Object has been created. |obj| must exist (its class and size are read)
 */
bool createObject(JSContext *cx, JSObject *obj);

/*
 * Object is about to be finalized. |obj| must still exist (its class is
 * read)
 */
bool finalizeObject(JSObject *obj);

/* JIT code observation */

enum JITReportGranularity {
    JITREPORT_GRANULARITY_NONE = 0,
    JITREPORT_GRANULARITY_FUNCTION = 1,
    JITREPORT_GRANULARITY_LINE = 2,
    JITREPORT_GRANULARITY_OP = 3
};

/*
 * Finest granularity of JIT information desired by all watchers.
 */
JITReportGranularity
JITGranularityRequested(JSContext *cx);

/*
 * A whole region of code has been deallocated, containing any number of ICs.
 * (ICs are unregistered in a batch, so individual ICs are not registered.)
 */
void
discardExecutableRegion(void *start, size_t size);

/*
 * Internal: DTrace-specific functions to be called during Probes::enterScript
 * and Probes::exitScript. These will not be inlined, but the argument
 * marshalling required for these probe points is expensive enough that it
 * shouldn't really matter.
 */
void DTraceEnterJSFun(JSContext *cx, JSFunction *fun, JSScript *script);
void DTraceExitJSFun(JSContext *cx, JSFunction *fun, JSScript *script);

} /* namespace Probes */

#ifdef INCLUDE_MOZILLA_DTRACE
static const char *ObjectClassname(JSObject *obj) {
    if (!obj)
        return "(null object)";
    Class *clasp = obj->getClass();
    if (!clasp)
        return "(null)";
    const char *class_name = clasp->name;
    if (!class_name)
        return "(null class name)";
    return class_name;
}
#endif

inline bool
Probes::createObject(JSContext *cx, JSObject *obj)
{
    bool ok = true;

#ifdef INCLUDE_MOZILLA_DTRACE
    if (JAVASCRIPT_OBJECT_CREATE_ENABLED())
        JAVASCRIPT_OBJECT_CREATE(ObjectClassname(obj), (uintptr_t)obj);
#endif

    return ok;
}

inline bool
Probes::finalizeObject(JSObject *obj)
{
    bool ok = true;

#ifdef INCLUDE_MOZILLA_DTRACE
    if (JAVASCRIPT_OBJECT_FINALIZE_ENABLED()) {
        Class *clasp = obj->getClass();

        /* the first arg is NULL - reserved for future use (filename?) */
        JAVASCRIPT_OBJECT_FINALIZE(NULL, (char *)clasp->name, (uintptr_t)obj);
    }
#endif

    return ok;
}

} /* namespace js */

#endif /* vm_Probes_h */