Reland of Remove slots that point to unboxed doubles from the StoreBuffer/SlotsBuffer.

src/heap/store-buffer.cc

Index: src/heap/store-buffer.cc
diff --git a/src/heap/store-buffer.cc b/src/heap/store-buffer.cc
index 37326e7e3f116b621ff02d71e77ec2f28dfaa090..f533431bb0de57bfdf45c404887d9edcddf79f01 100644
--- a/src/heap/store-buffer.cc
+++ b/src/heap/store-buffer.cc
@@ -247,6 +247,55 @@ void StoreBuffer::Filter(int flag) {
 }
 
 
+void StoreBuffer::RemoveSlots(Address start_address, Address end_address) {
+  struct IsValueInRangePredicate {
+    Address start_address_;
+    Address end_address_;
+
+    IsValueInRangePredicate(Address start_address, Address end_address)
+        : start_address_(start_address), end_address_(end_address) {}
+
+    bool operator()(Address addr) {
+      return start_address_ <= addr && addr < end_address_;
+    }
+  };
+
+  IsValueInRangePredicate predicate(start_address, end_address);
+  // Some address in old space that does not move.
+  const Address kRemovedSlot = heap_->undefined_value()->address();
+  DCHECK(Page::FromAddress(kRemovedSlot)->NeverEvacuate());
+
+  {
+    Address* top = reinterpret_cast<Address*>(heap_->store_buffer_top());
+    std::replace_if(start_, top, predicate, kRemovedSlot);
+  }
+
+  if (old_buffer_is_sorted_) {
+    // Remove slots from an old buffer preserving the order.
+    Address* lower = std::lower_bound(old_start_, old_top_, start_address);
+    if (lower != old_top_) {
+      // [lower, old_top_) range contain elements that are >= |start_address|.
+      Address* upper = std::lower_bound(lower, old_top_, end_address);
+      // Remove [lower, upper) from the buffer.
+      if (upper == old_top_) {
+        // All elements in [lower, old_top_) range are < |end_address|.
+        old_top_ = lower;
+      } else if (lower != upper) {
+        // [upper, old_top_) range contain elements that are >= |end_address|,
+        // move [upper, old_top_) range to [lower, ...) and update old_top_.
+        Address* new_top = lower;
+        for (Address* p = upper; p < old_top_; p++) {
+          *new_top++ = *p;
+        }
+        old_top_ = new_top;
+      }
+    }
+  } else {
+    std::replace_if(old_start_, old_top_, predicate, kRemovedSlot);
+  }
+}
+
+
 void StoreBuffer::SortUniq() {
   Compact();
   if (old_buffer_is_sorted_) return;
@@ -297,12 +346,18 @@ static Address* in_store_buffer_1_element_cache = NULL;
 
 
 bool StoreBuffer::CellIsInStoreBuffer(Address cell_address) {
-  if (!FLAG_enable_slow_asserts) return true;
+  DCHECK_NOT_NULL(cell_address);
+  Address* top = reinterpret_cast<Address*>(heap_->store_buffer_top());
   if (in_store_buffer_1_element_cache != NULL &&
       *in_store_buffer_1_element_cache == cell_address) {
-    return true;
+    // Check if the cache still points into the active part of the buffer.
+    if ((start_ <= in_store_buffer_1_element_cache &&
+         in_store_buffer_1_element_cache < top) ||
+        (old_start_ <= in_store_buffer_1_element_cache &&
+         in_store_buffer_1_element_cache < old_top_)) {
+      return true;
+    }
   }
-  Address* top = reinterpret_cast<Address*>(heap_->store_buffer_top());
   for (Address* current = top - 1; current >= start_; current--) {
     if (*current == cell_address) {
       in_store_buffer_1_element_cache = current;