Estimate a (close) upper bound on the size of black-marked objects on each page.

src/ia32/macro-assembler-ia32.h

 // Copyright 2011 the V8 project authors. All rights reserved.
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 // met:
 //
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@@ skipping 119 matching lines @@
   // then we just fall through, since it is already live.  If it is white and
   // we can determine that it doesn't need to be scanned, then we just mark it
   // black and fall through.  For the rest we jump to the label so the
   // incremental marker can fix its assumptions.
   void EnsureNotWhite(Register object,
                       Register scratch1,
                       Register scratch2,
                       Label* object_is_white_and_not_data,
                       Label::Distance distance);
 
-  // Detects conservatively whether an object is data-only, ie it does need to
-  // be scanned by the garbage collector.
-  void JumpIfDataObject(Register value,
-                        Register scratch,
-                        Label* not_data_object,
-                        Label::Distance not_data_object_distance);
-
   // Notify the garbage collector that we wrote a pointer into an object.
   // |object| is the object being stored into, |value| is the object being
   // stored.  value and scratch registers are clobbered by the operation.
   // The offset is the offset from the start of the object, not the offset from
   // the tagged HeapObject pointer.  For use with FieldOperand(reg, off).
   void RecordWriteField(
       Register object,
       int offset,
       Register value,
       Register scratch,
@@ skipping 639 matching lines @@
   // Helper for implementing JumpIfNotInNewSpace and JumpIfInNewSpace.
   void InNewSpace(Register object,
                   Register scratch,
                   Condition cc,
                   Label* condition_met,
                   Label::Distance condition_met_distance = Label::kFar);
 
   // Helper for finding the mark bits for an address.  Afterwards, the
   // bitmap register points at the word with the mark bits and the mask
   // the position of the first bit.  Uses ecx as scratch and leaves addr_reg
-  // unchanged.
+  // unchanged, unless it's also mask_reg.

[Erik Corry, 2011/06/24 09:46:17]

The implementation asserts that none of the registers are aliased so it seems
inconsistent for this comment to describe what happens if they are.

[Lasse Reichstein, 2011/06/24 11:09:08]

Ack, forgot to change comment back when I reverted my change to the function.

   inline void GetMarkBits(Register addr_reg,
                           Register bitmap_reg,
                           Register mask_reg);
 
   // Compute memory operands for safepoint stack slots.
   Operand SafepointRegisterSlot(Register reg);
   static int SafepointRegisterStackIndex(int reg_code);
 
   // Needs access to SafepointRegisterStackIndex for optimized frame
   // traversal.
@@ skipping 71 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_MACRO_ASSEMBLER_IA32_H_