gecko-dev/js/src/jsgcinlines.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 jsgcinlines_h
#define jsgcinlines_h

#include "jsgc.h"

#include "mozilla/DebugOnly.h"
#include "mozilla/Maybe.h"

#include "gc/GCTrace.h"
#include "gc/Zone.h"

namespace js {
namespace gc {

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

inline void
GCRuntime::poke()
{
    poked = true;

#ifdef JS_GC_ZEAL
    /* Schedule a GC to happen "soon" after a GC poke. */
    if (hasZealMode(ZealMode::Poke))
        nextScheduled = 1;
#endif
}

class ArenaIter
{
    Arena* arena;
    Arena* unsweptArena;
    Arena* sweptArena;
    mozilla::DebugOnly<bool> initialized;

  public:
    ArenaIter()
      : arena(nullptr), unsweptArena(nullptr), sweptArena(nullptr), initialized(false) {}

    ArenaIter(JS::Zone* zone, AllocKind kind) : initialized(false) { init(zone, kind); }

    void init(JS::Zone* zone, AllocKind kind) {
        MOZ_ASSERT(!initialized);
        MOZ_ASSERT(zone);
        initialized = true;
        arena = zone->arenas.getFirstArena(kind);
        unsweptArena = zone->arenas.getFirstArenaToSweep(kind);
        sweptArena = zone->arenas.getFirstSweptArena(kind);
        if (!unsweptArena) {
            unsweptArena = sweptArena;
            sweptArena = nullptr;
        }
        if (!arena) {
            arena = unsweptArena;
            unsweptArena = sweptArena;
            sweptArena = nullptr;
        }
    }

    bool done() const {
        MOZ_ASSERT(initialized);
        return !arena;
    }

    Arena* get() const {
        MOZ_ASSERT(!done());
        return arena;
    }

    void next() {
        MOZ_ASSERT(!done());
        arena = arena->next;
        if (!arena) {
            arena = unsweptArena;
            unsweptArena = sweptArena;
            sweptArena = nullptr;
        }
    }
};

class ArenaCellIterImpl
{
    size_t firstThingOffset;
    size_t thingSize;
    Arena* arenaAddr;
    FreeSpan span;
    uint_fast16_t thing;
    mozilla::DebugOnly<bool> initialized;

    // Upon entry, |thing| points to any thing (free or used) and finds the
    // first used thing, which may be |thing|.
    void moveForwardIfFree() {
        MOZ_ASSERT(!done());
        MOZ_ASSERT(thing);
        // Note: if |span| is empty, this test will fail, which is what we want
        // -- |span| being empty means that we're past the end of the last free
        // thing, all the remaining things in the arena are used, and we'll
        // never need to move forward.
        if (thing == span.first) {
            thing = span.last + thingSize;
            span = *span.nextSpan(arenaAddr);
        }
    }

  public:
    ArenaCellIterImpl()
      : firstThingOffset(0), thingSize(0), arenaAddr(nullptr), thing(0), initialized(false) {}

    explicit ArenaCellIterImpl(Arena* arena) : initialized(false) { init(arena); }

    void init(Arena* arena) {
        MOZ_ASSERT(!initialized);
        MOZ_ASSERT(arena);
        initialized = true;
        AllocKind kind = arena->getAllocKind();
        firstThingOffset = Arena::firstThingOffset(kind);
        thingSize = Arena::thingSize(kind);
        reset(arena);
    }

    // Use this to move from an Arena of a particular kind to another Arena of
    // the same kind.
    void reset(Arena* arena) {
        MOZ_ASSERT(initialized);
        MOZ_ASSERT(arena);
        arenaAddr = arena;
        span = *arena->getFirstFreeSpan();
        thing = firstThingOffset;
        moveForwardIfFree();
    }

    bool done() const {
        MOZ_ASSERT(initialized);
        MOZ_ASSERT(thing <= ArenaSize);
        return thing == ArenaSize;
    }

    TenuredCell* getCell() const {
        MOZ_ASSERT(!done());
        return reinterpret_cast<TenuredCell*>(uintptr_t(arenaAddr) + thing);
    }

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

    void next() {
        MOZ_ASSERT(!done());
        thing += thingSize;
        if (thing < ArenaSize)
            moveForwardIfFree();
    }
};

template<>
JSObject*
ArenaCellIterImpl::get<JSObject>() const;

class ArenaCellIterUnderGC : public ArenaCellIterImpl
{
  public:
    explicit ArenaCellIterUnderGC(Arena* arena) : ArenaCellIterImpl(arena) {
        MOZ_ASSERT(arena->zone->runtimeFromAnyThread()->isHeapBusy());
    }
};

class ArenaCellIterUnderFinalize : public ArenaCellIterImpl
{
  public:
    explicit ArenaCellIterUnderFinalize(Arena* arena) : ArenaCellIterImpl(arena) {}
};

class ZoneCellIterImpl
{
    ArenaIter arenaIter;
    ArenaCellIterImpl cellIter;

  public:
    ZoneCellIterImpl(JS::Zone* zone, AllocKind kind) {
        MOZ_ASSERT(zone);
        MOZ_ASSERT(zone->runtimeFromAnyThread()->gc.nursery.isEmpty());

        arenaIter.init(zone, kind);
        if (!arenaIter.done())
            cellIter.init(arenaIter.get());
    }

    bool done() const {
        return arenaIter.done();
    }

    template<typename T> T* get() const {
        MOZ_ASSERT(!done());
        return cellIter.get<T>();
    }

    Cell* getCell() const {
        MOZ_ASSERT(!done());
        return cellIter.getCell();
    }

    void next() {
        MOZ_ASSERT(!done());
        cellIter.next();
        if (cellIter.done()) {
            MOZ_ASSERT(!arenaIter.done());
            arenaIter.next();
            if (!arenaIter.done())
                cellIter.reset(arenaIter.get());
        }
    }
};

class ZoneCellIterUnderGC : public ZoneCellIterImpl
{
  public:
    ZoneCellIterUnderGC(JS::Zone* zone, AllocKind kind)
      : ZoneCellIterImpl(zone, kind)
    {
        MOZ_ASSERT(zone->runtimeFromAnyThread()->isHeapBusy());
    }
};

class ZoneCellIter
{
    mozilla::Maybe<ZoneCellIterImpl> impl;
    JS::AutoAssertNoAlloc noAlloc;

  public:
    ZoneCellIter(JS::Zone* zone, AllocKind kind) {
        // If called from outside a GC, ensure that the heap is in a state
        // that allows us to iterate.
        JSRuntime* rt = zone->runtimeFromMainThread();
        if (!rt->isHeapBusy()) {
            // We have a single-threaded runtime, so there's no need to protect
            // against other threads iterating or allocating. However, we do
            // have background finalization; we have to wait for this to finish
            // if it's currently active.
            if (IsBackgroundFinalized(kind) && zone->arenas.needBackgroundFinalizeWait(kind))
                rt->gc.waitBackgroundSweepEnd();

            // Evict the nursery before iterating so we can see all things.
            rt->gc.evictNursery();

            // Assert that no GCs can occur while a ZoneCellIter is live.
            noAlloc.disallowAlloc(rt);
        }

        impl.emplace(zone, kind);
    }

    bool done() const { return impl->done(); }
    template<typename T>
    T* get() const { return impl->get<T>(); }
    Cell* getCell() const { return impl->getCell(); }
    void next() { impl->next(); }
};

class GCZonesIter
{
  private:
    ZonesIter zone;

  public:
    explicit GCZonesIter(JSRuntime* rt, ZoneSelector selector = WithAtoms) : zone(rt, selector) {
        if (!zone->isCollecting())
            next();
    }

    bool done() const { return zone.done(); }

    void next() {
        MOZ_ASSERT(!done());
        do {
            zone.next();
        } while (!zone.done() && !zone->isCollectingFromAnyThread());
    }

    JS::Zone* get() const {
        MOZ_ASSERT(!done());
        return zone;
    }

    operator JS::Zone*() const { return get(); }
    JS::Zone* operator->() const { return get(); }
};

typedef CompartmentsIterT<GCZonesIter> GCCompartmentsIter;

/* Iterates over all zones in the current zone group. */
class GCZoneGroupIter {
  private:
    JS::Zone* current;

  public:
    explicit GCZoneGroupIter(JSRuntime* rt) {
        MOZ_ASSERT(rt->isHeapBusy());
        current = rt->gc.getCurrentZoneGroup();
    }

    bool done() const { return !current; }

    void next() {
        MOZ_ASSERT(!done());
        current = current->nextNodeInGroup();
    }

    JS::Zone* get() const {
        MOZ_ASSERT(!done());
        return current;
    }

    operator JS::Zone*() const { return get(); }
    JS::Zone* operator->() const { return get(); }
};

typedef CompartmentsIterT<GCZoneGroupIter> GCCompartmentGroupIter;

inline void
RelocationOverlay::forwardTo(Cell* cell)
{
    MOZ_ASSERT(!isForwarded());
    // The location of magic_ is important because it must never be valid to see
    // the value Relocated there in a GC thing that has not been moved.
    static_assert(offsetof(RelocationOverlay, magic_) == offsetof(JSObject, group_) &&
                  offsetof(RelocationOverlay, magic_) == offsetof(js::Shape, base_) &&
                  offsetof(RelocationOverlay, magic_) == offsetof(JSString, d.u1.flags),
                  "RelocationOverlay::magic_ is in the wrong location");
    newLocation_ = cell;
    magic_ = Relocated;
}

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

#endif /* jsgcinlines_h */