From d18b763359b3d624f93bb4280aeaa1908396bad7 Mon Sep 17 00:00:00 2001
From: "Gang Zhao (Hermes)" <zhaogang@meta.com>
Date: Tue, 10 Dec 2024 15:57:10 -0800
Subject: [PATCH] Pass the pointer of owning object in GCHermesValueBase::set()
 (#1512)

Summary:
Pull Request resolved: https://github.com/facebook/hermes/pull/1512

This variant will be used by write barriers that support large
allocation in following diffs.

Differential Revision: D62196480
---
 include/hermes/VM/HermesValue-inline.h | 30 ++++++++++++++++++++++++++
 include/hermes/VM/HermesValue.h        | 20 ++++++++++++++---
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/include/hermes/VM/HermesValue-inline.h b/include/hermes/VM/HermesValue-inline.h
index e60dfb6219e..5e4af784832 100644
--- a/include/hermes/VM/HermesValue-inline.h
+++ b/include/hermes/VM/HermesValue-inline.h
@@ -37,6 +37,18 @@ GCHermesValueBase<HVType>::GCHermesValueBase(HVType hv, GC &gc) : HVType{hv} {
     gc.constructorWriteBarrier(this, hv);
 }
 
+template <typename HVType>
+template <typename NeedsBarriers>
+GCHermesValueBase<HVType>::GCHermesValueBase(
+    HVType hv,
+    GC &gc,
+    const GCCell *owningObj)
+    : HVType{hv} {
+  assert(!hv.isPointer() || hv.getPointer());
+  if (NeedsBarriers::value)
+    gc.constructorWriteBarrierForLargeObj(owningObj, this, hv);
+}
+
 template <typename HVType>
 template <typename NeedsBarriers>
 GCHermesValueBase<HVType>::GCHermesValueBase(HVType hv, GC &gc, std::nullptr_t)
@@ -61,6 +73,24 @@ inline void GCHermesValueBase<HVType>::set(HVType hv, GC &gc) {
   HVType::setNoBarrier(hv);
 }
 
+template <typename HVType>
+template <typename NeedsBarriers>
+inline void GCHermesValueBase<HVType>::setInLarge(
+    HVType hv,
+    GC &gc,
+    const GCCell *owningObj) {
+  if (hv.isPointer()) {
+    HERMES_SLOW_ASSERT(
+        gc.validPointer(hv.getPointer(gc.getPointerBase())) &&
+        "Setting an invalid pointer into a GCHermesValue");
+  }
+  assert(NeedsBarriers::value || !gc.needsWriteBarrier(this, hv));
+  if constexpr (NeedsBarriers::value) {
+    gc.writeBarrierForLargeObj(owningObj, this, hv);
+  }
+  HVType::setNoBarrier(hv);
+}
+
 template <typename HVType>
 void GCHermesValueBase<HVType>::setNonPtr(HVType hv, GC &gc) {
   assert(!hv.isPointer());
diff --git a/include/hermes/VM/HermesValue.h b/include/hermes/VM/HermesValue.h
index 1dbd01effe5..45c37f61bdf 100644
--- a/include/hermes/VM/HermesValue.h
+++ b/include/hermes/VM/HermesValue.h
@@ -520,9 +520,15 @@ template <typename HVType>
 class GCHermesValueBase final : public HVType {
  public:
   GCHermesValueBase() : HVType(HVType::encodeUndefinedValue()) {}
-  /// Initialize a GCHermesValue from another HV. Performs a write barrier.
+  /// Initialize a GCHermesValue from another HV. Performs a write barrier. This
+  /// must not be used if it lives in an object that supports large allocation.
   template <typename NeedsBarriers = std::true_type>
   GCHermesValueBase(HVType hv, GC &gc);
+  /// Initialize a GCHermesValue from another HV. Performs a write barrier using
+  /// \p owningObj, which owns this GCHermesValue and may support large
+  /// allocation.
+  template <typename NeedsBarriers = std::true_type>
+  GCHermesValueBase(HVType hv, GC &gc, const GCCell *owningObj);
   /// Initialize a GCHermesValue from a non-pointer HV. Might perform a write
   /// barrier, depending on the GC.
   /// NOTE: The last parameter is unused, but acts as an overload selector.
@@ -530,11 +536,19 @@ class GCHermesValueBase final : public HVType {
   GCHermesValueBase(HVType hv, GC &gc, std::nullptr_t);
   GCHermesValueBase(const HVType &) = delete;
 
-  /// The HermesValue \p hv may be an object pointer.  Assign the
-  /// value, and perform any necessary write barriers.
+  /// The HermesValue \p hv may be an object pointer. Assign the value, and
+  /// perform any necessary write barriers. This must not be used if it lives in
+  /// an object that supports large allocation.
   template <typename NeedsBarriers = std::true_type>
   inline void set(HVType hv, GC &gc);
 
+  /// The HermesValue \p hv may be an object pointer. Assign the value, and
+  /// perform any necessary write barriers. \p owningObj is the object that
+  /// contains this GCHermesValueBase, and it may support large allocation.
+  /// for which the object pointer is needed by writer barriers.
+  template <typename NeedsBarriers = std::true_type>
+  inline void setInLarge(HVType hv, GC &gc, const GCCell *owningObj);
+
   /// The HermesValue \p hv must not be an object pointer.  Assign the
   /// value.
   /// Some GCs still need to do a write barrier though, so pass a GC parameter.