Move EmbedderHeapTracer::TracePrologue call to the beginning of full gc

src/heap/mark-compact.cc

 // Copyright 2012 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/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 842 matching lines @@
   if (was_marked_incrementally_ && heap_->ShouldAbortIncrementalMarking()) {
     heap()->incremental_marking()->Stop();
     ClearMarkbits();
     AbortWeakCollections();
     AbortWeakCells();
     AbortTransitionArrays();
     AbortCompaction();
     was_marked_incrementally_ = false;
   }
 
+  if (!was_marked_incrementally_) {
+    if (heap_->UsingEmbedderHeapTracer()) {
+      heap_->mark_compact_collector()->embedder_heap_tracer()->TracePrologue();

[Michael Lippautz, 2016/06/09 14:18:13]

Since we might abort incremental marking (just above) we potentially call
TracePrologue() twice. Is this ok?

+    }
+  }
+
   // Don't start compaction if we are in the middle of incremental
   // marking cycle. We did not collect any slots.
   if (!FLAG_never_compact && !was_marked_incrementally_) {
     StartCompaction(NON_INCREMENTAL_COMPACTION);
   }
 
   PagedSpaces spaces(heap());
   for (PagedSpace* space = spaces.next(); space != NULL;
        space = spaces.next()) {
     space->PrepareForMarkCompact();
@@ skipping 1440 matching lines @@
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WEAK_CLOSURE);
 
     // The objects reachable from the roots are marked, yet unreachable
     // objects are unmarked.  Mark objects reachable due to host
     // application specific logic or through Harmony weak maps.
     {
       TRACE_GC(heap()->tracer(),
                GCTracer::Scope::MC_MARK_WEAK_CLOSURE_EPHEMERAL);
-      if (UsingEmbedderHeapTracer()) {
-        embedder_heap_tracer()->TracePrologue();
-        ProcessMarkingDeque();
-      }
       ProcessEphemeralMarking(&root_visitor, false);
     }
 
     // The objects reachable from the roots, weak maps or object groups
     // are marked. Objects pointed to only by weak global handles cannot be
     // immediately reclaimed. Instead, we have to mark them as pending and mark
     // objects reachable from them.
     //
     // First we identify nonlive weak handles and mark them as pending
     // destruction.
@@ skipping 1655 matching lines @@
     MarkBit mark_bit = Marking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       RelocInfo rinfo(isolate(), pc, RelocInfo::CODE_TARGET, 0, host);
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8