Revert "[heap] Optimize NewSpace::AllocatedSinceLastGC"

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index a097fb3cf5503243ebed600f532c9757437825f8..91c9d0376eb16a7e7a5614863862f1074c8f5044 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -548,10 +548,6 @@ class MemoryChunk {
     return reinterpret_cast<MemoryChunk*>(OffsetFrom(a) & ~kAlignmentMask);
   }
 
-  static intptr_t OffsetInPage(Address a) {
-    return reinterpret_cast<intptr_t>(a) & kPageAlignmentMask;
-  }
-
   static inline MemoryChunk* FromAnyPointerAddress(Heap* heap, Address addr);
 
   static inline void UpdateHighWaterMark(Address mark) {
@@ -2529,7 +2525,6 @@ class NewSpace : public Space {
         from_space_(heap, kFromSpace),
         reservation_(),
         pages_used_(0),
-        allocated_since_last_gc_(0),
         top_on_previous_step_(0),
         allocated_histogram_(nullptr),
         promoted_histogram_(nullptr) {}
@@ -2601,7 +2596,42 @@ class NewSpace : public Space {
   // Return the available bytes without growing.
   intptr_t Available() override { return Capacity() - Size(); }
 
-  V8_INLINE size_t AllocatedSinceLastGC();
+  size_t AllocatedSinceLastGC() {
+    bool seen_age_mark = false;
+    Address age_mark = to_space_.age_mark();
+    Page* current_page = to_space_.first_page();
+    Page* age_mark_page = Page::FromAddress(age_mark);
+    Page* last_page = Page::FromAddress(top() - kPointerSize);
+    if (age_mark_page == last_page) {
+      if (top() - age_mark >= 0) {
+        return top() - age_mark;
+      }
+      // Top was reset at some point, invalidating this metric.
+      return 0;
+    }
+    while (current_page != last_page) {
+      if (current_page == age_mark_page) {
+        seen_age_mark = true;
+        break;
+      }
+      current_page = current_page->next_page();
+    }
+    if (!seen_age_mark) {
+      // Top was reset at some point, invalidating this metric.
+      return 0;
+    }
+    intptr_t allocated = age_mark_page->area_end() - age_mark;
+    DCHECK_EQ(current_page, age_mark_page);
+    current_page = age_mark_page->next_page();
+    while (current_page != last_page) {
+      allocated += Page::kAllocatableMemory;
+      current_page = current_page->next_page();
+    }
+    allocated += top() - current_page->area_start();
+    DCHECK_LE(0, allocated);
+    DCHECK_LE(allocated, Size());
+    return static_cast<size_t>(allocated);
+  }
 
   bool ReplaceWithEmptyPage(Page* page) {
     // This method is called after flipping the semispace.
@@ -2641,10 +2671,7 @@ class NewSpace : public Space {
   // Get the age mark of the inactive semispace.
   Address age_mark() { return from_space_.age_mark(); }
   // Set the age mark in the active semispace.
-  void set_age_mark(Address mark) {
-    to_space_.set_age_mark(mark);
-    allocated_since_last_gc_ = 0;
-  }
+  void set_age_mark(Address mark) { to_space_.set_age_mark(mark); }
 
   // The allocation top and limit address.
   Address* allocation_top_address() { return allocation_info_.top_address(); }
@@ -2765,7 +2792,6 @@ class NewSpace : public Space {
   SemiSpace from_space_;
   base::VirtualMemory reservation_;
   int pages_used_;
-  intptr_t allocated_since_last_gc_;
 
   // Allocation pointer and limit for normal allocation and allocation during
   // mark-compact collection.