[heap] More flag cleanup.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index aa63a00650ea3c4e8074e0786a80fce06a84819e..4bb07e08f80ea750cdf60c90e1dc9a4f1219b128 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -10,6 +10,7 @@
 
 #include "src/allocation.h"
 #include "src/assert-scope.h"
+#include "src/base/flags.h"
 #include "src/globals.h"
 #include "src/heap/gc-idle-time-handler.h"
 #include "src/heap/incremental-marking.h"
@@ -621,6 +622,23 @@ class Heap {
     kSmiRootsStart = kStringTableRootIndex + 1
   };
 
+  // Flags to indicate modes for a GC run.
+  enum GCFlag {
+    kNoGCFlags = 0u,
+    kReduceMemoryFootprintMask = 1u << 0,
+    kAbortIncrementalMarkingMask = 1u << 1,
+    kFinalizeIncrementalMarkingMask = 1u << 2,
+
+    // Making the heap iterable requires us to abort incremental marking.
+    kMakeHeapIterableMask = kAbortIncrementalMarkingMask,
+  };
+  typedef base::Flags<GCFlag> GCFlags;
+
+  enum GCFlagOverride {
+    kOverride,
+    kDontOverride,
+  };
+
   // Indicates whether live bytes adjustment is triggered
   // - from within the GC code before sweeping started (SEQUENTIAL_TO_SWEEPER),
   // - or from within GC (CONCURRENT_TO_SWEEPER),
@@ -643,6 +661,36 @@ class Heap {
     OBJECT_STATS_COUNT = FIRST_CODE_AGE_SUB_TYPE + Code::kCodeAgeCount + 1
   };
 
+  class GCFlagScope {
+   public:
+    GCFlagScope(Heap* heap, GCFlags gc_flags, GCCallbackFlags callback_flags,
+                GCFlagOverride override)
+        : heap_(heap), override_(override) {
+      if (override_ == kDontOverride) {
+        saved_gc_flags_ = heap->current_gc_flags_;
+        saved_gc_callback_flags_ = heap->current_gc_callback_flags_;
+      }
+      heap->set_current_gc_flags(gc_flags);
+      heap->current_gc_callback_flags_ = callback_flags;
+    }
+
+    ~GCFlagScope() {
+      if (override_ == kDontOverride) {
+        heap_->set_current_gc_flags(saved_gc_flags_);
+        heap_->current_gc_callback_flags_ = saved_gc_callback_flags_;
+      } else {
+        heap_->set_current_gc_flags(kNoGCFlags);
+        heap_->current_gc_callback_flags_ = kNoGCCallbackFlags;
+      }
+    }
+
+   private:
+    Heap* heap_;
+    GCFlagOverride override_;
+    GCFlags saved_gc_flags_;
+    GCCallbackFlags saved_gc_callback_flags_;
+  };
+
   // Taking this lock prevents the GC from entering a phase that relocates
   // object references.
   class RelocationLock {
@@ -745,14 +793,6 @@ class Heap {
   // callee is only valid in sloppy mode.
   static const int kArgumentsCalleeIndex = 1;
 
-  static const int kNoGCFlags = 0;
-  static const int kReduceMemoryFootprintMask = 1;
-  static const int kAbortIncrementalMarkingMask = 2;
-  static const int kFinalizeIncrementalMarkingMask = 4;
-
-  // Making the heap iterable requires us to abort incremental marking.
-  static const int kMakeHeapIterableMask = kAbortIncrementalMarkingMask;
-
   // The roots that have an index less than this are always in old space.
   static const int kOldSpaceRoots = 0x20;
 
@@ -1312,22 +1352,25 @@ class Heap {
   // Methods triggering GCs. ===================================================
   // ===========================================================================
 
-  // Performs garbage collection operation.
+  // Perform a garbage collection operation in a given space.
   // Returns whether there is a chance that another major GC could
   // collect more garbage.

[Hannes Payer (out of office), 2015/08/27 12:41:14]

Explain in detail here how the flags work.

   inline bool CollectGarbage(
-      AllocationSpace space, const char* gc_reason = NULL,
-      const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
+      AllocationSpace space, const char* gc_reason = nullptr,
+      const GCFlags flags = kNoGCFlags,
+      const GCCallbackFlags callback_flags = kNoGCCallbackFlags,
+      const GCFlagOverride override = kOverride);
+
+  inline bool CollectGarbageNewSpace(const char* gc_reason = nullptr);

[Hannes Payer (out of office), 2015/08/27 12:41:14]

Also mention here what impact the flags have.

 
-  // Performs a full garbage collection.  If (flags & kMakeHeapIterableMask) is
-  // non-zero, then the slower precise sweeper is used, which leaves the heap
-  // in a state where we can iterate over the heap visiting all objects.
+  // Performs a full garbage collection.
   void CollectAllGarbage(
-      int flags = kFinalizeIncrementalMarkingMask, const char* gc_reason = NULL,
+      const char* gc_reason = nullptr,
+      const GCFlags flags = Heap::kFinalizeIncrementalMarkingMask,
       const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
 
   // Last hope GC, should try to squeeze as much as possible.
-  void CollectAllAvailableGarbage(const char* gc_reason = NULL);
+  void CollectAllAvailableGarbage(const char* gc_reason = nullptr);
 
   // Invoked when GC was requested via the stack guard.
   void HandleGCRequest();
@@ -1376,7 +1419,7 @@ class Heap {
 
   // Starts incremental marking assuming incremental marking is currently
   // stopped.
-  void StartIncrementalMarking(int gc_flags = kNoGCFlags,
+  void StartIncrementalMarking(const GCFlags = kNoGCFlags,
                                const GCCallbackFlags gc_callback_flags =
                                    GCCallbackFlags::kNoGCCallbackFlags,
                                const char* reason = nullptr);
@@ -1687,7 +1730,7 @@ class Heap {
 
   StoreBuffer* store_buffer() { return &store_buffer_; }
 
-  void set_current_gc_flags(int flags) {
+  void set_current_gc_flags(GCFlags flags) {
     current_gc_flags_ = flags;
     DCHECK(!ShouldFinalizeIncrementalMarking() ||
            !ShouldAbortIncrementalMarking());
@@ -1729,17 +1772,13 @@ class Heap {
   // Performs garbage collection operation.
   // Returns whether there is a chance that another major GC could
   // collect more garbage.
-  bool CollectGarbage(
-      GarbageCollector collector, const char* gc_reason,
-      const char* collector_reason,
-      const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
+  bool CollectGarbage(GarbageCollector collector, const char* gc_reason,
+                      const char* collector_reason);
 
   // Performs garbage collection
   // Returns whether there is a chance another major GC could
   // collect more garbage.
-  bool PerformGarbageCollection(
-      GarbageCollector collector,
-      const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
+  bool PerformGarbageCollection(GarbageCollector collector);
 
   inline void UpdateOldSpaceLimits();
 
@@ -2359,7 +2398,7 @@ class Heap {
   bool configured_;
 
   // Currently set GC flags that are respected by all GC components.
-  int current_gc_flags_;
+  GCFlags current_gc_flags_;
 
   // Currently set GC callback flags that are used to pass information between
   // the embedder and V8's GC.