cppgc: More live bytes verification

Bug: chromium:1056170
Change-Id: I7d8d27f7497ec403dd463e0e2a5b3d0134cfb637
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2919960Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74817}

src/heap/cppgc/stats-collector.cc

@@ -42,11 +42,19 @@ void StatsCollector::NotifyAllocation(size_t bytes) {
   // The current GC may not have been started. This is ok as recording considers
   // the whole time range between garbage collections.
   allocated_bytes_since_safepoint_ += bytes;
+#ifdef CPPGC_VERIFY_LIVE_BYTES
+  DCHECK_GE(live_bytes_ + bytes, live_bytes_);
+  live_bytes_ += bytes;
+#endif  // CPPGC_VERIFY_LIVE_BYTES
 }
 
 void StatsCollector::NotifyExplicitFree(size_t bytes) {
   // See IncreaseAllocatedObjectSize for lifetime of the counter.
   explicitly_freed_bytes_since_safepoint_ += bytes;
+#ifdef CPPGC_VERIFY_LIVE_BYTES
+  DCHECK_GE(live_bytes_, bytes);
+  live_bytes_ -= bytes;
+#endif  // CPPGC_VERIFY_LIVE_BYTES
 }
 
 void StatsCollector::NotifySafePointForConservativeCollection() {
@@ -107,6 +115,9 @@ void StatsCollector::NotifyMarkingCompleted(size_t marked_bytes) {
       explicitly_freed_bytes_since_safepoint_;
   allocated_bytes_since_safepoint_ = 0;
   explicitly_freed_bytes_since_safepoint_ = 0;
+#ifdef CPPGC_VERIFY_LIVE_BYTES
+  live_bytes_ = marked_bytes;
+#endif  // CPPGC_VERIFY_LIVE_BYTES
 
   DCHECK_LE(memory_freed_bytes_since_end_of_marking_, memory_allocated_bytes_);
   memory_allocated_bytes_ -= memory_freed_bytes_since_end_of_marking_;

src/heap/cppgc/stats-collector.h

@@ -326,6 +326,9 @@ class V8_EXPORT_PRIVATE StatsCollector final {
   // arithmetic for simplicity.
   int64_t allocated_bytes_since_safepoint_ = 0;
   int64_t explicitly_freed_bytes_since_safepoint_ = 0;
+#ifdef CPPGC_VERIFY_LIVE_BYTES
+  size_t live_bytes_ = 0;
+#endif  // CPPGC_VERIFY_LIVE_BYTES
 
   int64_t memory_allocated_bytes_ = 0;
   int64_t memory_freed_bytes_since_end_of_marking_ = 0;