[heap] Introduce enum of garbage collection reasons.

src/heap/spaces.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/spaces.h"
 
 #include <utility>
 
 #include "src/base/bits.h"
 #include "src/base/platform/platform.h"
@@ skipping 2540 matching lines @@
   DCHECK(size_in_bytes <= kMaxBlockSize);
   DCHECK(IsAligned(size_in_bytes, kPointerSize));
   // Don't free list allocate if there is linear space available.
   DCHECK(owner_->limit() - owner_->top() < size_in_bytes);
 
   // Mark the old linear allocation area with a free space map so it can be
   // skipped when scanning the heap.  This also puts it back in the free list
   // if it is big enough.
   owner_->EmptyAllocationInfo();
 
-  owner_->heap()->StartIncrementalMarkingIfNeeded(
-      Heap::kNoGCFlags, kNoGCCallbackFlags, "old space step");
+  owner_->heap()->StartIncrementalMarkingIfAllocationLimitIsReached(
+      Heap::kNoGCFlags, kNoGCCallbackFlags);
 
   int new_node_size = 0;
   FreeSpace* new_node = FindNodeFor(size_in_bytes, &new_node_size);
   if (new_node == nullptr) return nullptr;
 
   int bytes_left = new_node_size - size_in_bytes;
   DCHECK(bytes_left >= 0);
 
 #ifdef DEBUG
   for (int i = 0; i < size_in_bytes / kPointerSize; i++) {
@@ skipping 415 matching lines @@
   MSAN_ALLOCATED_UNINITIALIZED_MEMORY(object->address(), object_size);
 
   if (Heap::ShouldZapGarbage()) {
     // Make the object consistent so the heap can be verified in OldSpaceStep.
     // We only need to do this in debug builds or if verify_heap is on.
     reinterpret_cast<Object**>(object->address())[0] =
         heap()->fixed_array_map();
     reinterpret_cast<Object**>(object->address())[1] = Smi::FromInt(0);
   }
 
-  heap()->StartIncrementalMarkingIfNeeded(Heap::kNoGCFlags, kNoGCCallbackFlags,
-                                          "old space step");
+  heap()->StartIncrementalMarkingIfAllocationLimitIsReached(Heap::kNoGCFlags,
+                                                            kNoGCCallbackFlags);
   AllocationStep(object->address(), object_size);
 
   if (heap()->incremental_marking()->black_allocation()) {
     Marking::MarkBlack(ObjectMarking::MarkBitFrom(object));
     MemoryChunk::IncrementLiveBytesFromGC(object, object_size);
   }
   return object;
 }
 
 
@@ skipping 219 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8