Correctly format builtin constructors in stack traces

src/objects.h

 // Copyright 2015 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/assert-scope.h"
@@ skipping 5056 matching lines @@
   // [is_turbofanned]: For kind STUB or OPTIMIZED_FUNCTION, tells whether the
   // code object was generated by the TurboFan optimizing compiler.
   inline bool is_turbofanned();
   inline void set_is_turbofanned(bool value);
 
   // [can_have_weak_objects]: For kind OPTIMIZED_FUNCTION, tells whether the
   // embedded objects in code should be treated weakly.
   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();
   inline void set_has_deoptimization_support(bool value);
 
   // [has_debug_break_slots]: For FUNCTION kind, tells if it has
   // been compiled with debug break slots.
   inline bool has_debug_break_slots();
   inline void set_has_debug_break_slots(bool value);
 
@@ skipping 315 matching lines @@
                         PlatformSmiTagging::kSmiValueSize -
                             HasUnwindingInfoField::kNext + 1> {};
 
   // KindSpecificFlags1 layout (STUB, BUILTIN and OPTIMIZED_FUNCTION)
   static const int kStackSlotsFirstBit = 0;
   static const int kStackSlotsBitCount = 24;
   static const int kMarkedForDeoptimizationBit =
       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
   class MarkedForDeoptimizationField
       : public BitField<bool, kMarkedForDeoptimizationBit, 1> {};  // NOLINT
   class IsTurbofannedField : public BitField<bool, kIsTurbofannedBit, 1> {
   };  // 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;
   class IsCrankshaftedField: public BitField<bool,
       kIsCrankshaftedBit, 1> {};  // NOLINT
 
   // KindSpecificFlags2 layout (STUB and OPTIMIZED_FUNCTION)
   static const int kSafepointTableOffsetFirstBit = kIsCrankshaftedBit + 1;
   static const int kSafepointTableOffsetBitCount = 30;
 
@@ skipping 5536 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_