[heap] Make external_memory_concurrently_freed_ unsigned

to avoid undefined behavior on signed integer overflow.

Change-Id: Ib55b427723a81dddc26f3ce4b2b3b8cc69c9c017
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1782166
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63526}

src/heap/array-buffer-tracker-inl.h

@@ -80,8 +80,7 @@ void LocalArrayBufferTracker::Free(Callback should_free) {
         ExternalBackingStoreType::kArrayBuffer, freed_memory);
 
     // TODO(wez): Remove backing-store from external memory accounting.
-    page_->heap()->update_external_memory_concurrently_freed(
-        static_cast<intptr_t>(freed_memory));
+    page_->heap()->update_external_memory_concurrently_freed(freed_memory);
   }
 }
 

src/heap/array-buffer-tracker.cc

@@ -68,8 +68,7 @@ void LocalArrayBufferTracker::Process(Callback callback) {
     page_->DecrementExternalBackingStoreBytes(
         ExternalBackingStoreType::kArrayBuffer, freed_memory);
     // TODO(wez): Remove backing-store from external memory accounting.
-    page_->heap()->update_external_memory_concurrently_freed(
-        static_cast<intptr_t>(freed_memory));
+    page_->heap()->update_external_memory_concurrently_freed(freed_memory);
   }
 
   array_buffers_.swap(kept_array_buffers);

src/heap/heap-inl.h

@@ -67,7 +67,7 @@ void Heap::update_external_memory(int64_t delta) {
   isolate()->isolate_data()->external_memory_ += delta;
 }
 
-void Heap::update_external_memory_concurrently_freed(intptr_t freed) {
+void Heap::update_external_memory_concurrently_freed(uintptr_t freed) {
   external_memory_concurrently_freed_ += freed;
 }
 

src/heap/heap.h

@@ -585,7 +585,7 @@ class Heap {
 
   V8_INLINE int64_t external_memory();
   V8_INLINE void update_external_memory(int64_t delta);
-  V8_INLINE void update_external_memory_concurrently_freed(intptr_t freed);
+  V8_INLINE void update_external_memory_concurrently_freed(uintptr_t freed);
   V8_INLINE void account_external_memory_concurrently_freed();
 
   size_t backing_store_bytes() const { return backing_store_bytes_; }
@@ -1802,7 +1802,7 @@ class Heap {
 #endif  // DEBUG
 
   // The amount of memory that has been freed concurrently.
-  std::atomic<intptr_t> external_memory_concurrently_freed_{0};
+  std::atomic<uintptr_t> external_memory_concurrently_freed_{0};
 
   // This can be calculated directly from a pointer to the heap; however, it is
   // more expedient to get at the isolate directly from within Heap methods.