Correctly format builtin constructors in stack traces

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 9671c9ba74e62530a026175e5a801d107eb8c595..2e742c3603b1a2aa4f7a3084962dff14d03bf378 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5074,6 +5074,12 @@ class Code: public HeapObject {
   inline bool can_have_weak_objects();
   inline void set_can_have_weak_objects(bool value);
 
+  // [is_construct_stub]: For kind BUILTIN, tells whether the code object
+  // represents a hand-written construct stub
+  // (e.g., NumberConstructor_ConstructStub).
+  inline bool is_construct_stub();
+  inline void set_is_construct_stub(bool value);
+
   // [has_deoptimization_support]: For FUNCTION kind, tells if it has
   // deoptimization support.
   inline bool has_deoptimization_support();
@@ -5409,9 +5415,10 @@ class Code: public HeapObject {
       kStackSlotsFirstBit + kStackSlotsBitCount;
   static const int kIsTurbofannedBit = kMarkedForDeoptimizationBit + 1;
   static const int kCanHaveWeakObjects = kIsTurbofannedBit + 1;
+  static const int kIsConstructStub = kCanHaveWeakObjects + 1;

[Yang, 2016/07/08 07:08:04]

We could be smarter here. Aside from IsTurbofannedBit, none of the existing
fields is used for BUILTIN. And the IsTurbofannedBit is actually not relevant
for BUILTIN either, so we could just only set it if the code kind is
OPTIMIZED_FUNCTION.

So we could actually choose 0 for kIsConstructStub to reuse the bit.

That being said, I would also be fine with leaving this as is and simply add a
comment for the future, since we still have a bunch of bits left at this point.

[jgruber, 2016/07/08 10:02:41]

Done.

 
   STATIC_ASSERT(kStackSlotsFirstBit + kStackSlotsBitCount <= 32);
-  STATIC_ASSERT(kCanHaveWeakObjects + 1 <= 32);
+  STATIC_ASSERT(kIsConstructStub + 1 <= 32);
 
   class StackSlotsField: public BitField<int,
       kStackSlotsFirstBit, kStackSlotsBitCount> {};  // NOLINT
@@ -5421,6 +5428,8 @@ class Code: public HeapObject {
   };  // NOLINT
   class CanHaveWeakObjectsField
       : public BitField<bool, kCanHaveWeakObjects, 1> {};  // NOLINT
+  class IsConstructStubField : public BitField<bool, kIsConstructStub, 1> {
+  };  // NOLINT
 
   // KindSpecificFlags2 layout (ALL)
   static const int kIsCrankshaftedBit = 0;