Pass the pointer of owning object to GCPointer constructor and set me…

…thod (#1502)

Summary: Pull Request resolved: #1502

Differential Revision: D62222257

include/hermes/VM/GCPointer-inline.h

@@ -32,6 +32,21 @@ GCPointerBase::GCPointerBase(
   }
 }
 
+GCPointerBase::GCPointerBase(
+    PointerBase &base,
+    GCCell *ptr,
+    GC &gc,
+    const GCCell *owningObj)
+    : CompressedPointer(CompressedPointer::encode(ptr, base)) {
+  assert(
+      (!ptr || gc.validPointer(ptr)) &&
+      "Cannot construct a GCPointer from an invalid pointer");
+  // Constructing a GCPointer on an object that supports large allocation always
+  // needs to perform write barrier. We may revisit this decision if we see a
+  // case that needs optimization.
+  gc.constructorWriteBarrierForLargeObj(owningObj, this, ptr);
+}
+
 inline void GCPointerBase::set(PointerBase &base, GCCell *ptr, GC &gc) {
   assert(
       (!ptr || gc.validPointer(ptr)) &&
@@ -59,6 +74,44 @@ GCPointerBase::set(PointerBase &base, CompressedPointer ptr, GC &gc) {
   setNoBarrier(ptr);
 }
 
+inline void GCPointerBase::setInLargeObj(
+    PointerBase &base,
+    GCCell *ptr,
+    GC &gc,
+    const GCCell *owningObj) {
+  assert(
+      (!ptr || gc.validPointer(ptr)) &&
+      "Cannot set a GCPointer to an invalid pointer");
+  // Write barrier must happen before the write.
+  gc.writeBarrierForLargeObj(owningObj, this, ptr);
+  setNoBarrier(CompressedPointer::encode(ptr, base));
+}
+
+inline void GCPointerBase::setNonNullInLargeObj(
+    PointerBase &base,
+    GCCell *ptr,
+    GC &gc,
+    const GCCell *owningObj) {
+  assert(
+      gc.validPointer(ptr) && "Cannot set a GCPointer to an invalid pointer");
+  // Write barrier must happen before the write.
+  gc.writeBarrierForLargeObj(owningObj, this, ptr);
+  setNoBarrier(CompressedPointer::encodeNonNull(ptr, base));
+}
+
+inline void GCPointerBase::setInLargeObj(
+    PointerBase &base,
+    CompressedPointer ptr,
+    GC &gc,
+    const GCCell *owningObj) {
+  assert(
+      (!ptr || gc.validPointer(ptr.get(base))) &&
+      "Cannot set a GCPointer to an invalid pointer");
+  // Write barrier must happen before the write.
+  gc.writeBarrierForLargeObj(owningObj, this, ptr.get(base));
+  setNoBarrier(ptr);
+}
+
 inline void GCPointerBase::setNull(GC &gc) {
   gc.snapshotWriteBarrier(this);
   setNoBarrier(CompressedPointer(nullptr));

include/hermes/VM/GCPointer.h

@@ -27,21 +27,51 @@ class GCPointerBase : public CompressedPointer {
   template <typename NeedsBarriers>
   inline GCPointerBase(PointerBase &base, GCCell *ptr, GC &gc, NeedsBarriers);
 
+  inline GCPointerBase(
+      PointerBase &base,
+      GCCell *ptr,
+      GC &gc,
+      const GCCell *owningObj);
+
  public:
   // These classes are used as arguments to GCPointer constructors, to
   // indicate whether write barriers are necessary in initializing the
   // GCPointer.
   class NoBarriers : public std::false_type {};
   class YesBarriers : public std::true_type {};
 
-  /// This must be used to assign a new value to this GCPointer.
+  /// This must be used to assign a new value to this GCPointer. This must not
+  /// be used if it lives in an object that supports large allocation.
   /// \param ptr The memory being pointed to.
   /// \param base The base of ptr.
   /// \param gc Used for write barriers.
   inline void set(PointerBase &base, GCCell *ptr, GC &gc);
   inline void set(PointerBase &base, CompressedPointer ptr, GC &gc);
   inline void setNonNull(PointerBase &base, GCCell *ptr, GC &gc);
 
+  /// This must be used to assign a new value to this GCPointer, which lives in
+  /// an object of kind that supports large allocation.
+  /// \param ptr The memory being pointed to.
+  /// \param base The base of ptr.
+  /// \param gc Used for write barriers.
+  /// \param owningObj The object that contains this GCPointer, used by the
+  /// writer barriers.
+  inline void setInLargeObj(
+      PointerBase &base,
+      GCCell *ptr,
+      GC &gc,
+      const GCCell *owningObj);
+  inline void setInLargeObj(
+      PointerBase &base,
+      CompressedPointer ptr,
+      GC &gc,
+      const GCCell *owningObj);
+  inline void setNonNullInLargeObj(
+      PointerBase &base,
+      GCCell *ptr,
+      GC &gc,
+      const GCCell *owningObj);
+
   /// Set this pointer to null. This needs a write barrier in some types of
   /// garbage collectors.
   inline void setNull(GC &gc);
@@ -64,12 +94,26 @@ class GCPointer : public GCPointerBase {
   template <typename NeedsBarriers>
   GCPointer(PointerBase &base, T *ptr, GC &gc, NeedsBarriers needsBarriers)
       : GCPointerBase(base, ptr, gc, needsBarriers) {}
+  /// Pass the owning object pointer to perform barriers when the object
+  /// supports large allocation.
+  template <typename NeedsBarriers>
+  GCPointer(
+      PointerBase &base,
+      T *ptr,
+      GC &gc,
+      const GCCell *owningObj,
+      NeedsBarriers needsBarriers)
+      : GCPointerBase(base, ptr, gc, owningObj, needsBarriers) {}
 
   /// Same as the constructor above, with the default for
   /// NeedsBarriers as "YesBarriers".  (We can't use default template
   /// arguments with the idiom used above.)
-  inline GCPointer(PointerBase &base, T *ptr, GC &gc)
+  GCPointer(PointerBase &base, T *ptr, GC &gc)
       : GCPointer<T>(base, ptr, gc, YesBarriers()) {}
+  /// Pass the owning object pointer to perform barriers when the object
+  /// supports large allocation.
+  GCPointer(PointerBase &base, T *ptr, GC &gc, const GCCell *owningObj)
+      : GCPointer<T>(base, ptr, gc, owningObj, YesBarriers()) {}
 
   /// We are not allowed to copy-construct or assign GCPointers.
   GCPointer(const GCPointerBase &) = delete;
@@ -86,7 +130,8 @@ class GCPointer : public GCPointerBase {
     return vmcast<T>(GCPointerBase::getNonNull(base));
   }
 
-  /// Assign a new value to this GCPointer.
+  /// Assign a new value to this GCPointer. This must not be used if it lives in
+  /// an object that supports large allocation.
   /// \param base The base of ptr.
   /// \param ptr The memory being pointed to.
   /// \param gc Used for write barriers.
@@ -97,10 +142,40 @@ class GCPointer : public GCPointerBase {
     GCPointerBase::setNonNull(base, ptr, gc);
   }
 
-  /// Convenience overload of GCPointer::set for other GCPointers.
+  /// Assign a new value to this GCPointer, which lives in an object of kind
+  /// that supports large allocation.
+  /// \param base The base of ptr.
+  /// \param ptr The memory being pointed to.
+  /// \param gc Used for write barriers.
+  /// \param owningObj The object that contains this GCPointer, used by the
+  /// writer barriers.
+  void
+  setInLargeObj(PointerBase &base, T *ptr, GC &gc, const GCCell *owningObj) {
+    GCPointerBase::set(base, ptr, gc, owningObj);
+  }
+  void setNonNullInLargeObj(
+      PointerBase &base,
+      T *ptr,
+      GC &gc,
+      const GCCell *owningObj) {
+    GCPointerBase::setNonNull(base, ptr, gc, owningObj);
+  }
+
+  /// Convenience overload of GCPointer::set for other GCPointers. This must not
+  /// be used if it lives in an object that supports large allocation.
   void set(PointerBase &base, const GCPointer<T> &ptr, GC &gc) {
     GCPointerBase::set(base, ptr, gc);
   }
+
+  /// Convenience overload of GCPointer::set for other GCPointers. \p owningObj
+  /// is used by the writer barriers.
+  void setInLargeObj(
+      PointerBase &base,
+      const GCPointer<T> &ptr,
+      GC &gc,
+      const GCCell *owningObj) {
+    GCPointerBase::set(base, ptr, gc, owningObj);
+  }
 };
 
 } // namespace vm