gecko-dev/js/src/jsgcinlines.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is SpiderMonkey code.
 *
 * The Initial Developer of the Original Code is
 * Mozilla Corporation.
 * Portions created by the Initial Developer are Copyright (C) 2010
 * the Initial Developer. All Rights Reserved.
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 * Contributor(s):
 *
 *
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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 * ***** END LICENSE BLOCK ***** */

#ifndef jsgcinlines_h___
#define jsgcinlines_h___

#include "jsgc.h"
#include "jscntxt.h"
#include "jscompartment.h"
#include "jslock.h"
#include "jsscope.h"
#include "jsxml.h"

#include "js/TemplateLib.h"

namespace js {

struct Shape;

namespace gc {

inline JSGCTraceKind
GetGCThingTraceKind(const void *thing)
{
    JS_ASSERT(thing);
    const Cell *cell = reinterpret_cast<const Cell *>(thing);
    return MapAllocToTraceKind(cell->getAllocKind());
}

/* Capacity for slotsToThingKind */
const size_t SLOTS_TO_THING_KIND_LIMIT = 17;

/* Get the best kind to use when making an object with the given slot count. */
static inline AllocKind
GetGCObjectKind(size_t numSlots)
{
    extern AllocKind slotsToThingKind[];

    if (numSlots >= SLOTS_TO_THING_KIND_LIMIT)
        return FINALIZE_OBJECT16;
    return slotsToThingKind[numSlots];
}

static inline AllocKind
GetGCObjectKind(Class *clasp)
{
    if (clasp == &FunctionClass)
        return JSFunction::FinalizeKind;
    uint32_t nslots = JSCLASS_RESERVED_SLOTS(clasp);
    if (clasp->flags & JSCLASS_HAS_PRIVATE)
        nslots++;
    return GetGCObjectKind(nslots);
}

/* As for GetGCObjectKind, but for dense array allocation. */
static inline AllocKind
GetGCArrayKind(size_t numSlots)
{
    extern AllocKind slotsToThingKind[];

    /*
     * Dense arrays can use their fixed slots to hold their elements array
     * (less two Values worth of ObjectElements header), but if more than the
     * maximum number of fixed slots is needed then the fixed slots will be
     * unused.
     */
    JS_STATIC_ASSERT(ObjectElements::VALUES_PER_HEADER == 2);
    if (numSlots > JSObject::NELEMENTS_LIMIT || numSlots + 2 >= SLOTS_TO_THING_KIND_LIMIT)
        return FINALIZE_OBJECT2;
    return slotsToThingKind[numSlots + 2];
}

static inline AllocKind
GetGCObjectFixedSlotsKind(size_t numFixedSlots)
{
    extern AllocKind slotsToThingKind[];

    JS_ASSERT(numFixedSlots < SLOTS_TO_THING_KIND_LIMIT);
    return slotsToThingKind[numFixedSlots];
}

static inline bool
IsBackgroundAllocKind(AllocKind kind)
{
    JS_ASSERT(kind <= FINALIZE_OBJECT_LAST);
    return kind % 2 == 1;
}

static inline AllocKind
GetBackgroundAllocKind(AllocKind kind)
{
    JS_ASSERT(!IsBackgroundAllocKind(kind));
    return (AllocKind) (kind + 1);
}

/*
 * Try to get the next larger size for an object, keeping BACKGROUND
 * consistent.
 */
static inline bool
TryIncrementAllocKind(AllocKind *kindp)
{
    size_t next = size_t(*kindp) + 2;
    if (next >= size_t(FINALIZE_OBJECT_LIMIT))
        return false;
    *kindp = AllocKind(next);
    return true;
}

/* Get the number of fixed slots and initial capacity associated with a kind. */
static inline size_t
GetGCKindSlots(AllocKind thingKind)
{
    /* Using a switch in hopes that thingKind will usually be a compile-time constant. */
    switch (thingKind) {
      case FINALIZE_OBJECT0:
      case FINALIZE_OBJECT0_BACKGROUND:
        return 0;
      case FINALIZE_OBJECT2:
      case FINALIZE_OBJECT2_BACKGROUND:
        return 2;
      case FINALIZE_OBJECT4:
      case FINALIZE_OBJECT4_BACKGROUND:
        return 4;
      case FINALIZE_OBJECT8:
      case FINALIZE_OBJECT8_BACKGROUND:
        return 8;
      case FINALIZE_OBJECT12:
      case FINALIZE_OBJECT12_BACKGROUND:
        return 12;
      case FINALIZE_OBJECT16:
      case FINALIZE_OBJECT16_BACKGROUND:
        return 16;
      default:
        JS_NOT_REACHED("Bad object finalize kind");
        return 0;
    }
}

static inline size_t
GetGCKindSlots(AllocKind thingKind, Class *clasp)
{
    size_t nslots = GetGCKindSlots(thingKind);

    /* An object's private data uses the space taken by its last fixed slot. */
    if (clasp->flags & JSCLASS_HAS_PRIVATE) {
        JS_ASSERT(nslots > 0);
        nslots--;
    }

    /*
     * Functions have a larger finalize kind than FINALIZE_OBJECT to reserve
     * space for the extra fields in JSFunction, but have no fixed slots.
     */
    if (clasp == &FunctionClass)
        nslots = 0;

    return nslots;
}

static inline void
GCPoke(JSRuntime *rt, Value oldval)
{
    /*
     * Since we're forcing a GC from JS_GC anyway, don't bother wasting cycles
     * loading oldval.  XXX remove implied force, fix jsinterp.c's "second arg
     * ignored", etc.
     */
#if 1
    rt->gcPoke = true;
#else
    rt->gcPoke = oldval.isGCThing();
#endif

#ifdef JS_GC_ZEAL
    /* Schedule a GC to happen "soon" after a GC poke. */
    if (rt->gcZeal() == js::gc::ZealPokeValue)
        rt->gcNextScheduled = 1;
#endif
}

/*
 * Invoke ArenaOp and CellOp on every arena and cell in a compartment which
 * have the specified thing kind.
 */
template <class ArenaOp, class CellOp>
void
ForEachArenaAndCell(JSCompartment *compartment, AllocKind thingKind,
                    ArenaOp arenaOp, CellOp cellOp)
{
    size_t thingSize = Arena::thingSize(thingKind);
    ArenaHeader *aheader = compartment->arenas.getFirstArena(thingKind);

    for (; aheader; aheader = aheader->next) {
        Arena *arena = aheader->getArena();
        arenaOp(arena);
        FreeSpan firstSpan(aheader->getFirstFreeSpan());
        const FreeSpan *span = &firstSpan;

        for (uintptr_t thing = arena->thingsStart(thingKind); ; thing += thingSize) {
            JS_ASSERT(thing <= arena->thingsEnd());
            if (thing == span->first) {
                if (!span->hasNext())
                    break;
                thing = span->last;
                span = span->nextSpan();
            } else {
                Cell *t = reinterpret_cast<Cell *>(thing);
                cellOp(t);
            }
        }
    }
}

class CellIterImpl
{
    size_t firstThingOffset;
    size_t thingSize;
    ArenaHeader *aheader;
    FreeSpan firstSpan;
    const FreeSpan *span;
    uintptr_t thing;
    Cell *cell;

  protected:
    CellIterImpl() {
    }

    void initSpan(JSCompartment *comp, AllocKind kind) {
        JS_ASSERT(comp->arenas.isSynchronizedFreeList(kind));
        firstThingOffset = Arena::firstThingOffset(kind);
        thingSize = Arena::thingSize(kind);
        firstSpan.initAsEmpty();
        span = &firstSpan;
        thing = span->first;
    }

    void init(ArenaHeader *singleAheader) {
        aheader = singleAheader;
        initSpan(aheader->compartment, aheader->getAllocKind());
        next();
        aheader = NULL;
    }

    void init(JSCompartment *comp, AllocKind kind) {
        initSpan(comp, kind);
        aheader = comp->arenas.getFirstArena(kind);
        next();
    }

  public:
    bool done() const {
        return !cell;
    }

    template<typename T> T *get() const {
        JS_ASSERT(!done());
        return static_cast<T *>(cell);
    }

    Cell *getCell() const {
        JS_ASSERT(!done());
        return cell;
    }

    void next() {
        for (;;) {
            if (thing != span->first)
                break;
            if (JS_LIKELY(span->hasNext())) {
                thing = span->last + thingSize;
                span = span->nextSpan();
                break;
            }
            if (!aheader) {
                cell = NULL;
                return;
            }
            firstSpan = aheader->getFirstFreeSpan();
            span = &firstSpan;
            thing = aheader->arenaAddress() | firstThingOffset;
            aheader = aheader->next;
        }
        cell = reinterpret_cast<Cell *>(thing);
        thing += thingSize;
    }
};

class CellIterUnderGC : public CellIterImpl
{
  public:
    CellIterUnderGC(JSCompartment *comp, AllocKind kind) {
        JS_ASSERT(comp->rt->gcRunning);
        init(comp, kind);
    }

    CellIterUnderGC(ArenaHeader *aheader) {
        JS_ASSERT(aheader->compartment->rt->gcRunning);
        init(aheader);
    }
};

/*
 * When using the iterator outside the GC the caller must ensure that no GC or
 * allocations of GC things are possible and that the background finalization
 * for the given thing kind is not enabled or is done.
 */
class CellIter : public CellIterImpl
{
    ArenaLists *lists;
    AllocKind kind;
#ifdef DEBUG
    size_t *counter;
#endif
  public:
    CellIter(JSContext *cx, JSCompartment *comp, AllocKind kind)
      : lists(&comp->arenas),
        kind(kind)
    {
#ifdef JS_THREADSAFE
        JS_ASSERT(comp->arenas.doneBackgroundFinalize(kind));
#endif
        if (lists->isSynchronizedFreeList(kind)) {
            lists = NULL;
        } else {
            JS_ASSERT(!comp->rt->gcRunning);
            lists->copyFreeListToArena(kind);
        }
#ifdef DEBUG
        counter = &cx->runtime->noGCOrAllocationCheck;
        ++*counter;
#endif
        init(comp, kind);
    }

    ~CellIter() {
#ifdef DEBUG
        JS_ASSERT(*counter > 0);
        --*counter;
#endif
        if (lists)
            lists->clearFreeListInArena(kind);
    }
};

/* Signatures for ArenaOp and CellOp above. */

inline void EmptyArenaOp(Arena *arena) {}
inline void EmptyCellOp(Cell *t) {}

/*
 * Allocates a new GC thing. After a successful allocation the caller must
 * fully initialize the thing before calling any function that can potentially
 * trigger GC. This will ensure that GC tracing never sees junk values stored
 * in the partially initialized thing.
 */

template <typename T>
inline T *
NewGCThing(JSContext *cx, js::gc::AllocKind kind, size_t thingSize)
{
    JS_ASSERT(thingSize == js::gc::Arena::thingSize(kind));
#ifdef JS_THREADSAFE
    JS_ASSERT_IF((cx->compartment == cx->runtime->atomsCompartment),
                 kind == js::gc::FINALIZE_STRING || kind == js::gc::FINALIZE_SHORT_STRING);
#endif
    JS_ASSERT(!cx->runtime->gcRunning);
    JS_ASSERT(!cx->runtime->noGCOrAllocationCheck);

#ifdef JS_GC_ZEAL
    if (cx->runtime->needZealousGC())
        js::gc::RunDebugGC(cx);
#endif

    js::gc::MaybeCheckStackRoots(cx);

    JSCompartment *comp = cx->compartment;
    void *t = comp->arenas.allocateFromFreeList(kind, thingSize);
    if (!t)
        t = js::gc::ArenaLists::refillFreeList(cx, kind);

    JS_ASSERT_IF(t && comp->needsBarrier(),
                 static_cast<T *>(t)->arenaHeader()->allocatedDuringIncremental);
    return static_cast<T *>(t);
}

/* Alternate form which allocates a GC thing if doing so cannot trigger a GC. */
template <typename T>
inline T *
TryNewGCThing(JSContext *cx, js::gc::AllocKind kind, size_t thingSize)
{
    JS_ASSERT(thingSize == js::gc::Arena::thingSize(kind));
#ifdef JS_THREADSAFE
    JS_ASSERT_IF((cx->compartment == cx->runtime->atomsCompartment),
                 kind == js::gc::FINALIZE_STRING || kind == js::gc::FINALIZE_SHORT_STRING);
#endif
    JS_ASSERT(!cx->runtime->gcRunning);
    JS_ASSERT(!cx->runtime->noGCOrAllocationCheck);

#ifdef JS_GC_ZEAL
    if (cx->runtime->needZealousGC())
        return NULL;
#endif

    void *t = cx->compartment->arenas.allocateFromFreeList(kind, thingSize);
    JS_ASSERT_IF(t && cx->compartment->needsBarrier(),
                 static_cast<T *>(t)->arenaHeader()->allocatedDuringIncremental);
    return static_cast<T *>(t);
}

} /* namespace gc */
} /* namespace js */

inline JSObject *
js_NewGCObject(JSContext *cx, js::gc::AllocKind kind)
{
    JS_ASSERT(kind >= js::gc::FINALIZE_OBJECT0 && kind <= js::gc::FINALIZE_OBJECT_LAST);
    return js::gc::NewGCThing<JSObject>(cx, kind, js::gc::Arena::thingSize(kind));
}

inline JSObject *
js_TryNewGCObject(JSContext *cx, js::gc::AllocKind kind)
{
    JS_ASSERT(kind >= js::gc::FINALIZE_OBJECT0 && kind <= js::gc::FINALIZE_OBJECT_LAST);
    return js::gc::TryNewGCThing<JSObject>(cx, kind, js::gc::Arena::thingSize(kind));
}

inline JSString *
js_NewGCString(JSContext *cx)
{
    return js::gc::NewGCThing<JSString>(cx, js::gc::FINALIZE_STRING, sizeof(JSString));
}

inline JSShortString *
js_NewGCShortString(JSContext *cx)
{
    return js::gc::NewGCThing<JSShortString>(cx, js::gc::FINALIZE_SHORT_STRING, sizeof(JSShortString));
}

inline JSExternalString *
js_NewGCExternalString(JSContext *cx)
{
    return js::gc::NewGCThing<JSExternalString>(cx, js::gc::FINALIZE_EXTERNAL_STRING,
                                                sizeof(JSExternalString));
}

inline JSScript *
js_NewGCScript(JSContext *cx)
{
    return js::gc::NewGCThing<JSScript>(cx, js::gc::FINALIZE_SCRIPT, sizeof(JSScript));
}

inline js::Shape *
js_NewGCShape(JSContext *cx)
{
    return js::gc::NewGCThing<js::Shape>(cx, js::gc::FINALIZE_SHAPE, sizeof(js::Shape));
}

inline js::BaseShape *
js_NewGCBaseShape(JSContext *cx)
{
    return js::gc::NewGCThing<js::BaseShape>(cx, js::gc::FINALIZE_BASE_SHAPE, sizeof(js::BaseShape));
}

#if JS_HAS_XML_SUPPORT
extern JSXML *
js_NewGCXML(JSContext *cx);
#endif

#endif /* jsgcinlines_h___ */