From 65d37979bc5932d68507897c9895b36850081b26 Mon Sep 17 00:00:00 2001
From: "Gang Zhao (Hermes)" <zhaogang@meta.com>
Date: Thu, 7 Nov 2024 17:15:55 -0800
Subject: [PATCH] Pass the pointer of owning object in GCPointer::set() part I
 (#1502)

Summary: Pull Request resolved: https://github.com/facebook/hermes/pull/1502

Differential Revision: D62222257
---
 include/hermes/VM/GCPointer-inline.h | 30 +++++++++++------
 include/hermes/VM/GCPointer.h        | 49 +++++++++++++++++++++++++---
 2 files changed, 65 insertions(+), 14 deletions(-)

diff --git a/include/hermes/VM/GCPointer-inline.h b/include/hermes/VM/GCPointer-inline.h
index fa5f7633ed5..0eef539cfc4 100644
--- a/include/hermes/VM/GCPointer-inline.h
+++ b/include/hermes/VM/GCPointer-inline.h
@@ -32,21 +32,31 @@ GCPointerBase::GCPointerBase(
   }
 }
 
-inline void GCPointerBase::set(PointerBase &base, GCCell *ptr, GC &gc) {
+template <typename MaybeLargeObj, typename NonNull>
+inline void GCPointerBase::setImpl(
+    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.writeBarrier(this, ptr);
-  setNoBarrier(CompressedPointer::encode(ptr, base));
-}
+  (void)owningObj;
+  if constexpr (MaybeLargeObj::value) {
+    assert(
+        owningObj &&
+        "The cell pointer must be provided for cell kind that supports large allocation");
 
-inline void GCPointerBase::setNonNull(PointerBase &base, GCCell *ptr, GC &gc) {
-  assert(
-      gc.validPointer(ptr) && "Cannot set a GCPointer to an invalid pointer");
-  // Write barrier must happen before the write.
-  gc.writeBarrier(this, ptr);
-  setNoBarrier(CompressedPointer::encodeNonNull(ptr, base));
+    gc.writeBarrier(this, ptr);
+  } else {
+    gc.writeBarrier(this, ptr);
+  }
+  if constexpr (NonNull::value) {
+    setNoBarrier(CompressedPointer::encodeNonNull(ptr, base));
+  } else {
+    setNoBarrier(CompressedPointer::encode(ptr, base));
+  }
 }
 
 inline void
diff --git a/include/hermes/VM/GCPointer.h b/include/hermes/VM/GCPointer.h
index 09db5f06d87..7af0bb258ac 100644
--- a/include/hermes/VM/GCPointer.h
+++ b/include/hermes/VM/GCPointer.h
@@ -34,17 +34,45 @@ class GCPointerBase : public CompressedPointer {
   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, GCCell *ptr, GC &gc) {
+    setImpl<std::false_type, std::false_type>(base, ptr, gc, nullptr);
+  }
   inline void set(PointerBase &base, CompressedPointer ptr, GC &gc);
-  inline void setNonNull(PointerBase &base, GCCell *ptr, GC &gc);
+  inline void setNonNull(PointerBase &base, GCCell *ptr, GC &gc) {
+    setImpl<std::false_type, std::true_type>(base, ptr, gc, nullptr);
+  }
+
+  /// This must be used to assign a new value to this GCPointer.
+  /// \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
+  set(PointerBase &base, GCCell *ptr, GC &gc, const GCCell *owningObj) {
+    setImpl<std::true_type, std::false_type>(base, ptr, gc, owningObj);
+  }
+  inline void
+  setNonNull(PointerBase &base, GCCell *ptr, GC &gc, const GCCell *owningObj) {
+    setImpl<std::true_type, std::true_type>(base, ptr, gc, owningObj);
+  }
 
   /// Set this pointer to null. This needs a write barrier in some types of
   /// garbage collectors.
   inline void setNull(GC &gc);
+
+ private:
+  /// Implementation details shared by all set* functions here.
+  /// \tparam MaybeLargeObj Whether the owning object supports large allocation.
+  /// If it is false, \p owningObj is not used by the writer barriers.
+  /// \tparam NonNull Whether \p is non null.
+  template <typename MaybeLargeObj, typename NonNull>
+  void setImpl(PointerBase &base, GCCell *ptr, GC &gc, const GCCell *owningObj);
 };
 
 /// A class to represent "raw" pointers to heap objects.  Disallows assignment,
@@ -86,7 +114,8 @@ 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.
@@ -97,6 +126,18 @@ class GCPointer : public GCPointerBase {
     GCPointerBase::setNonNull(base, ptr, gc);
   }
 
+  /// Assign a new value to this GCPointer.
+  /// \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 set(PointerBase &base, T *ptr, GC &gc, const GCCell *owningObj) {
+    GCPointerBase::set(base, ptr, gc, owningObj);
+  }
+  void setNonNull(PointerBase &base, T *ptr, GC &gc, const GCCell *owningObj) {
+    GCPointerBase::setNonNull(base, ptr, gc, owningObj);
+  }
+
   /// Convenience overload of GCPointer::set for other GCPointers.
   void set(PointerBase &base, const GCPointer<T> &ptr, GC &gc) {
     GCPointerBase::set(base, ptr, gc);