/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * 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/. */

/*
 * Trace methods for all GC things, defined in a separate header to allow
 * inlining.
 *
 * This also includes eager inline marking versions. Both paths must end up
 * traversing equivalent subgraphs.
 */

#ifndef gc_TraceMethods_inl_h
#define gc_TraceMethods_inl_h

#include "mozilla/Likely.h"

#include "gc/GCMarker.h"
#include "gc/Tracer.h"
#include "jit/JitCode.h"
#include "vm/BigIntType.h"
#include "vm/GetterSetter.h"
#include "vm/GlobalObject.h"
#include "vm/JSScript.h"
#include "vm/PropMap.h"
#include "vm/Realm.h"
#include "vm/Scope.h"
#include "vm/Shape.h"
#include "vm/StringType.h"
#include "vm/SymbolType.h"
#include "wasm/WasmJS.h"

#include "gc/BufferAllocator-inl.h"
#include "gc/Marking-inl.h"
#include "vm/StringType-inl.h"

inline void js::BaseScript::traceChildren(JSTracer* trc) {
  TraceNullableEdge(trc, &function_, "function");
  TraceEdge(trc, &sourceObject_, "sourceObject");

  if (data_) {
    TraceBufferEdge(trc, this, &data_, "PrivateScriptData");
    data_->trace(trc);
  }

  warmUpData_.trace(trc);
}

inline void js::Shape::traceChildren(JSTracer* trc) {
  TraceCellHeaderEdge(trc, this, "base");
  if (isNative()) {
    asNative().traceChildren(trc);
  }
}

inline void js::NativeShape::traceChildren(JSTracer* trc) {
  TraceNullableEdge(trc, &propMap_, "propertymap");
}

template <uint32_t opts>
void js::GCMarker::eagerlyMarkChildren(Shape* shape) {
  MOZ_ASSERT(shape->isMarked(markColor()));

  BaseShape* base = shape->base();
  markAndTraverseEdge<opts>(shape, base);

  if (shape->isNative()) {
    if (PropMap* map = shape->asNative().propMap()) {
      markAndTraverseEdge<opts>(shape, map);
    }
  }
}

inline void js::BaseShape::traceChildren(JSTracer* trc) {
  // Note: the realm's global can be nullptr if we GC while creating the global.
  JSObject* global = realm()->unsafeUnbarrieredMaybeGlobal();
  if (MOZ_LIKELY(global)) {
    TraceManuallyBarrieredEdge(trc, &global, "baseshape_global");
  }

  if (proto_.isObject()) {
    TraceEdge(trc, &proto_, "baseshape_proto");
  }
}

template <uint32_t opts>
void js::GCMarker::eagerlyMarkChildren(BaseShape* base) {
  JSObject* global = base->realm()->unsafeUnbarrieredMaybeGlobal();
  if (MOZ_LIKELY(global)) {
    markAndTraverseEdge<opts>(base, global);
  }

  TaggedProto proto = base->proto();
  if (proto.isObject()) {
    markAndTraverseEdge<opts>(base, proto.toObject());
  }
}

inline void JSString::traceChildren(JSTracer* trc) {
  // Concurrent marking uses the other path.
  MOZ_ASSERT(!js::IsConcurrentMarkingTracer(trc));

  if (hasBase()) {
    traceBase(trc);
  } else if (isRope()) {
    asRope().traceChildren(trc);
  }
}
template <uint32_t opts>
void js::GCMarker::eagerlyMarkChildren(JSString* str) {
  uint32_t flags = str->flags();
  if (flags & js::StringFlags::LINEAR_BIT) {
    eagerlyMarkChildren<opts>(static_cast<JSLinearString*>(str));
  } else {
    eagerlyMarkChildren<opts>(static_cast<JSRope*>(str));
  }
}

inline void JSString::traceBase(JSTracer* trc) {
  MOZ_ASSERT(hasBase());
  js::TraceManuallyBarrieredEdge(trc, &d.s.u3.base, "base");
}
template <uint32_t opts>
void js::GCMarker::eagerlyMarkChildren(JSLinearString* linearStr) {
  gc::AssertShouldMarkInZone(this, linearStr);
  MOZ_ASSERT(linearStr->isMarkedAny());

  // Use iterative marking to avoid blowing out the stack.
  while (linearStr->hasBase()) {
    linearStr = linearStr->base();

    // It's possible to observe a rope as the base of a linear string if we
    // process barriers during rope flattening. See the assignment of base in
    // JSRope::flattenInternal's finish_node section.
    if (static_cast<JSString*>(linearStr)->isRope()) {
      MOZ_ASSERT(!JS::RuntimeHeapIsMajorCollecting());
      break;
    }

    MOZ_ASSERT(linearStr->JSString::isLinear());
    gc::AssertShouldMarkInZone(this, linearStr);
    if (!mark<opts>(static_cast<JSString*>(linearStr))) {
      break;
    }
  }
}

inline void JSRope::traceChildren(JSTracer* trc) {
  // Concurrent marking uses the other path.
  MOZ_ASSERT(!js::IsConcurrentMarkingTracer(trc));

  js::TraceManuallyBarrieredEdge(trc, &d.s.u2.left, "left child");
  js::TraceManuallyBarrieredEdge(trc, &d.s.u3.right, "right child");
}
template <uint32_t opts>
void js::GCMarker::eagerlyMarkChildren(JSRope* rope) {
  // This function tries to scan the whole rope tree using the marking stack as
  // temporary storage. If that becomes full, the unscanned ropes are added to
  // the delayed marking list. When the function returns, the marking stack is
  // at the same depth as it was on entry and ropes never leak to other users of
  // the stack. This also assumes that a rope can only point to other ropes or
  // linear strings, it cannot refer to GC things of other types.

  size_t savedPos = stack.position();
  MOZ_DIAGNOSTIC_ASSERT(rope->getTraceKind() == JS::TraceKind::String);

  while (true) {
    MOZ_DIAGNOSTIC_ASSERT(rope->getTraceKind() == JS::TraceKind::String);
    gc::AssertShouldMarkInZone(this, rope);

    MOZ_ASSERT(rope->isMarkedAny());
    JSRope* next = nullptr;

    JSString* left = rope->leftChild();
    JSString* right = rope->rightChild();

#ifdef JS_GC_CONCURRENT_MARKING
    // Check for a change of type performed by the main thread. This uses
    // fence/fence synchronisation with the atomic operation being the update to
    // the string flags.
    //
    // If we observe a change we skip marking the string here. This string will
    // be marked by main thread.
    //
    // We care about the following transitions here:
    //  - rope => dependent string (rope flattening)
    //  - rope => extensible string (rope flattening)
    //  - rope => atom ref
    //
    // The order of operations is important here: we read the child fields,
    // perform the memory fence and then check the flags. When changing the type
    // on the main thread these happen in the reverse order. This ensures that
    // we can't observe updated children with the old type. Observing the new
    // type with old children is possible but benign.
    if constexpr (bool(opts & gc::MarkingOptions::ConcurrentMarking)) {
      gc::MemoryAcquireFence<opts>(rope->runtimeFromAnyThread());
      if (!rope->isRopeAtomic()) {
        continue;
      }
    }
#else
    MOZ_DIAGNOSTIC_ASSERT(rope->JSString::isRope());
#endif

    if (mark<opts>(right)) {
      MOZ_ASSERT(!right->isPermanentAtom());
      if (right->isLinear()) {
        eagerlyMarkChildren<opts>(static_cast<JSLinearString*>(right));
      } else {
        next = static_cast<JSRope*>(right);
      }
    }

    if (mark<opts>(left)) {
      MOZ_ASSERT(!left->isPermanentAtom());
      if (left->isLinear()) {
        eagerlyMarkChildren<opts>(static_cast<JSLinearString*>(left));
      } else {
        // When both children are ropes, set aside the right one to
        // scan it later.
        if (next && !stack.pushTempRope(next)) {
          delayMarkingChildrenOnOOM(next);
        }
        next = static_cast<JSRope*>(left);
      }
    }
    if (next) {
      rope = next;
    } else if (savedPos != stack.position()) {
      MOZ_ASSERT(savedPos < stack.position());
      rope = stack.popPtr().asTempRope();
    } else {
      break;
    }
  }

  MOZ_ASSERT(savedPos == stack.position());
}

inline void JS::Symbol::traceChildren(JSTracer* trc) {
  js::TraceNullableCellHeaderEdge(trc, this, "symbol description");
}

template <typename SlotInfo>
void js::RuntimeScopeData<SlotInfo>::trace(JSTracer* trc) {
  TraceBindingNames(trc, GetScopeDataTrailingNamesPointer(this), length);
}

inline void js::FunctionScope::RuntimeData::trace(JSTracer* trc) {
  TraceNullableEdge(trc, &canonicalFunction, "scope canonical function");
  TraceNullableBindingNames(trc, GetScopeDataTrailingNamesPointer(this),
                            length);
}
inline void js::ModuleScope::RuntimeData::trace(JSTracer* trc) {
  TraceNullableEdge(trc, &module, "scope module");
  TraceBindingNames(trc, GetScopeDataTrailingNamesPointer(this), length);
}
inline void js::WasmInstanceScope::RuntimeData::trace(JSTracer* trc) {
  TraceNullableEdge(trc, &instance, "wasm instance");
  TraceBindingNames(trc, GetScopeDataTrailingNamesPointer(this), length);
}

inline void js::Scope::traceChildren(JSTracer* trc) {
  TraceNullableEdge(trc, &environmentShape_, "scope env shape");
  TraceNullableEdge(trc, &enclosingScope_, "scope enclosing");
  BaseScopeData* data = rawData();
  if (data) {
    TraceBufferEdge(trc, this, &data, "Scope data");
    if (data != rawData()) {
      setHeaderPtr(data);
    }
    applyScopeDataTyped([trc](auto data) { data->trace(trc); });
  }
}

template <uint32_t opts>
void js::GCMarker::eagerlyMarkChildren(Scope* scope) {
  do {
    if (Shape* shape = scope->environmentShape()) {
      markAndTraverseEdge<opts>(scope, shape);
    }
    if (BaseScopeData* data = scope->rawData()) {
      MarkTenuredBuffer(scope->zone(), data);
    }
    mozilla::Span<AbstractBindingName<JSAtom>> names;
    switch (scope->kind()) {
      case ScopeKind::Function: {
        FunctionScope::RuntimeData& data = scope->as<FunctionScope>().data();
        if (data.canonicalFunction) {
          markAndTraverseObjectEdge<opts>(scope, data.canonicalFunction);
        }
        names = GetScopeDataTrailingNames(&data);
        break;
      }

      case ScopeKind::FunctionBodyVar: {
        VarScope::RuntimeData& data = scope->as<VarScope>().data();
        names = GetScopeDataTrailingNames(&data);
        break;
      }

      case ScopeKind::Lexical:
      case ScopeKind::SimpleCatch:
      case ScopeKind::Catch:
      case ScopeKind::NamedLambda:
      case ScopeKind::StrictNamedLambda:
      case ScopeKind::FunctionLexical: {
        LexicalScope::RuntimeData& data = scope->as<LexicalScope>().data();
        names = GetScopeDataTrailingNames(&data);
        break;
      }

      case ScopeKind::ClassBody: {
        ClassBodyScope::RuntimeData& data = scope->as<ClassBodyScope>().data();
        names = GetScopeDataTrailingNames(&data);
        break;
      }

      case ScopeKind::Global:
      case ScopeKind::NonSyntactic: {
        GlobalScope::RuntimeData& data = scope->as<GlobalScope>().data();
        names = GetScopeDataTrailingNames(&data);
        break;
      }

      case ScopeKind::Eval:
      case ScopeKind::StrictEval: {
        EvalScope::RuntimeData& data = scope->as<EvalScope>().data();
        names = GetScopeDataTrailingNames(&data);
        break;
      }

      case ScopeKind::Module: {
        ModuleScope::RuntimeData& data = scope->as<ModuleScope>().data();
        if (data.module) {
          markAndTraverseObjectEdge<opts>(scope, data.module);
        }
        names = GetScopeDataTrailingNames(&data);
        break;
      }

      case ScopeKind::With:
        break;

      case ScopeKind::WasmInstance: {
        WasmInstanceScope::RuntimeData& data =
            scope->as<WasmInstanceScope>().data();
        markAndTraverseObjectEdge<opts>(scope, data.instance);
        names = GetScopeDataTrailingNames(&data);
        break;
      }

      case ScopeKind::WasmFunction: {
        WasmFunctionScope::RuntimeData& data =
            scope->as<WasmFunctionScope>().data();
        names = GetScopeDataTrailingNames(&data);
        break;
      }
    }
    if (scope->kind_ == ScopeKind::Function) {
      for (auto& binding : names) {
        if (JSAtom* name = binding.name()) {
          markAndTraverseStringEdge<opts>(scope, name);
        }
      }
    } else {
      for (auto& binding : names) {
        markAndTraverseStringEdge<opts>(scope, binding.name());
      }
    }
    scope = scope->enclosing();
  } while (scope && mark<opts>(scope));
}

inline void js::GetterSetter::traceChildren(JSTracer* trc) {
  if (getter()) {
    TraceCellHeaderEdge(trc, this, "gettersetter_getter");
  }
  if (setter()) {
    TraceEdge(trc, &setter_, "gettersetter_setter");
  }
}

inline void js::PropMap::traceChildren(JSTracer* trc) {
  if (hasPrevious()) {
    TraceEdge(trc, &asLinked()->data_.previous, "propmap_previous");
  }

  if (isShared()) {
    SharedPropMap::TreeData& treeData = asShared()->treeDataRef();
    if (SharedPropMap* parent = treeData.parent.maybeMap()) {
      TraceManuallyBarrieredEdge(trc, &parent, "propmap_parent");
      if (parent != treeData.parent.map()) {
        treeData.setParent(parent, treeData.parent.index());
      }
    }
  }

  for (uint32_t i = 0; i < PropMap::Capacity; i++) {
    if (hasKey(i)) {
      TraceEdge(trc, &keys_[i], "propmap_key");
    }
  }

  if (canHaveTable() && asLinked()->hasTable()) {
    asLinked()->data_.table->trace(trc);
  }
}

template <uint32_t opts>
void js::GCMarker::eagerlyMarkChildren(PropMap* map) {
  MOZ_ASSERT(map->isMarkedAny());
  do {
    for (uint32_t i = 0; i < PropMap::Capacity; i++) {
      if (map->hasKey(i)) {
        markAndTraverseEdge<opts>(map, map->getKey(i));
      }
    }

    if (map->canHaveTable()) {
      // Special case: if a map has a table then all its pointers must point to
      // this map or an ancestor. Since these pointers will be traced by this
      // loop they do not need to be traced here as well.
      MOZ_ASSERT_IF(state != MarkingState::ConcurrentMarking,
                    map->asLinked()->canSkipMarkingTable());
    }

    if (map->isDictionary()) {
      map = map->asDictionary()->previous();
    } else {
      // For shared maps follow the |parent| link and not the |previous| link.
      // They're different when a map had a branch that wasn't at the end of the
      // map, but in this case they must have the same |previous| map. This is
      // asserted in SharedPropMap::addChild. In other words, marking all
      // |parent| maps will also mark all |previous| maps.
      map = map->asShared()->treeDataRef().parent.maybeMap();
    }
  } while (map && mark<opts>(map));
}

inline void JS::BigInt::traceChildren(JSTracer* trc) {
  if (!hasInlineDigits()) {
    js::TraceBufferEdge(trc, this, &heapDigits_, "BigInt::heapDigits_");
  }
}

// JitCode::traceChildren is not defined inline due to its dependence on
// MacroAssembler.

#endif  // gc_TraceMethods_inl_h