1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/js/src/gc/Nursery-inl.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,86 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
1.5 + * vim: set ts=4 sw=4 et tw=79 ft=cpp:
1.6 + *
1.7 + * This Source Code Form is subject to the terms of the Mozilla Public
1.8 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.9 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.10 +
1.11 +#ifndef gc_Nursery_inl_h
1.12 +#define gc_Nursery_inl_h
1.13 +
1.14 +#ifdef JSGC_GENERATIONAL
1.15 +
1.16 +#include "gc/Nursery.h"
1.17 +
1.18 +#include "gc/Heap.h"
1.19 +
1.20 +namespace js {
1.21 +namespace gc {
1.22 +
1.23 +/*
1.24 + * This structure overlays a Cell in the Nursery and re-purposes its memory
1.25 + * for managing the Nursery collection process.
1.26 + */
1.27 +class RelocationOverlay
1.28 +{
1.29 + friend class MinorCollectionTracer;
1.30 +
1.31 + /* The low bit is set so this should never equal a normal pointer. */
1.32 + static const uintptr_t Relocated = uintptr_t(0xbad0bad1);
1.33 +
1.34 + /* Set to Relocated when moved. */
1.35 + uintptr_t magic_;
1.36 +
1.37 + /* The location |this| was moved to. */
1.38 + Cell *newLocation_;
1.39 +
1.40 + /* A list entry to track all relocated things. */
1.41 + RelocationOverlay *next_;
1.42 +
1.43 + public:
1.44 + static RelocationOverlay *fromCell(Cell *cell) {
1.45 + JS_ASSERT(!cell->isTenured());
1.46 + return reinterpret_cast<RelocationOverlay *>(cell);
1.47 + }
1.48 +
1.49 + bool isForwarded() const {
1.50 + return magic_ == Relocated;
1.51 + }
1.52 +
1.53 + Cell *forwardingAddress() const {
1.54 + JS_ASSERT(isForwarded());
1.55 + return newLocation_;
1.56 + }
1.57 +
1.58 + void forwardTo(Cell *cell) {
1.59 + JS_ASSERT(!isForwarded());
1.60 + magic_ = Relocated;
1.61 + newLocation_ = cell;
1.62 + next_ = nullptr;
1.63 + }
1.64 +
1.65 + RelocationOverlay *next() const {
1.66 + return next_;
1.67 + }
1.68 +};
1.69 +
1.70 +} /* namespace gc */
1.71 +} /* namespace js */
1.72 +
1.73 +template <typename T>
1.74 +MOZ_ALWAYS_INLINE bool
1.75 +js::Nursery::getForwardedPointer(T **ref)
1.76 +{
1.77 + JS_ASSERT(ref);
1.78 + JS_ASSERT(isInside(*ref));
1.79 + const gc::RelocationOverlay *overlay = reinterpret_cast<const gc::RelocationOverlay *>(*ref);
1.80 + if (!overlay->isForwarded())
1.81 + return false;
1.82 + /* This static cast from Cell* restricts T to valid (GC thing) types. */
1.83 + *ref = static_cast<T *>(overlay->forwardingAddress());
1.84 + return true;
1.85 +}
1.86 +
1.87 +#endif /* JSGC_GENERATIONAL */
1.88 +
1.89 +#endif /* gc_Nursery_inl_h */
