Improve write barriers in optimized code.

src/ia32/macro-assembler-ia32.h

 // 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.
 
 #ifndef V8_IA32_MACRO_ASSEMBLER_IA32_H_
 #define V8_IA32_MACRO_ASSEMBLER_IA32_H_
 
 #include "src/assembler.h"
 #include "src/frames.h"
 #include "src/globals.h"
 
 namespace v8 {
 namespace internal {
 
 // Convenience for platform-independent signatures.  We do not normally
 // distinguish memory operands from other operands on ia32.
 typedef Operand MemOperand;
 
 enum RememberedSetAction { EMIT_REMEMBERED_SET, OMIT_REMEMBERED_SET };
 enum SmiCheck { INLINE_SMI_CHECK, OMIT_SMI_CHECK };
+enum PointersToHereCheck {
+  kPointersToHereMaybeInteresting,
+  kPointersToHereAreAlwaysInteresting
+};
 
 
 enum RegisterValueType {
   REGISTER_VALUE_IS_SMI,
   REGISTER_VALUE_IS_INT32
 };
 
 
 bool AreAliased(Register r1, Register r2, Register r3, Register r4);
 
@@ skipping 102 matching lines @@
   // 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,
       SaveFPRegsMode save_fp,
       RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
-      SmiCheck smi_check = INLINE_SMI_CHECK);
+      SmiCheck smi_check = INLINE_SMI_CHECK,
+      PointersToHereCheck pointers_to_here_check_for_value =
+          kPointersToHereMaybeInteresting);
 
   // As above, but the offset has the tag presubtracted.  For use with
   // Operand(reg, off).
   void RecordWriteContextSlot(
       Register context,
       int offset,
       Register value,
       Register scratch,
       SaveFPRegsMode save_fp,
       RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
-      SmiCheck smi_check = INLINE_SMI_CHECK) {
+      SmiCheck smi_check = INLINE_SMI_CHECK,
+      PointersToHereCheck pointers_to_here_check_for_value =
+          kPointersToHereMaybeInteresting) {
     RecordWriteField(context,
                      offset + kHeapObjectTag,
                      value,
                      scratch,
                      save_fp,
                      remembered_set_action,
-                     smi_check);
+                     smi_check,
+                     pointers_to_here_check_for_value);
   }
 
   // Notify the garbage collector that we wrote a pointer into a fixed array.
   // |array| is the array being stored into, |value| is the
   // object being stored.  |index| is the array index represented as a
   // Smi. All registers are clobbered by the operation RecordWriteArray
   // filters out smis so it does not update the write barrier if the
   // value is a smi.
   void RecordWriteArray(
       Register array,
       Register value,
       Register index,
       SaveFPRegsMode save_fp,
       RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
-      SmiCheck smi_check = INLINE_SMI_CHECK);
+      SmiCheck smi_check = INLINE_SMI_CHECK,
+      PointersToHereCheck pointers_to_here_check_for_value =
+          kPointersToHereMaybeInteresting);
 
   // For page containing |object| mark region covering |address|
   // dirty. |object| is the object being stored into, |value| is the
   // object being stored. The address and value registers are clobbered by the
   // operation. RecordWrite filters out smis so it does not update the
   // write barrier if the value is a smi.
   void RecordWrite(
       Register object,
       Register address,
       Register value,
       SaveFPRegsMode save_fp,
       RememberedSetAction remembered_set_action = EMIT_REMEMBERED_SET,
-      SmiCheck smi_check = INLINE_SMI_CHECK);
+      SmiCheck smi_check = INLINE_SMI_CHECK,
+      PointersToHereCheck pointers_to_here_check_for_value =
+          kPointersToHereMaybeInteresting);
 
   // For page containing |object| mark the region covering the object's map
   // dirty. |object| is the object being stored into, |map| is the Map object
   // that was stored.
   void RecordWriteForMap(
       Register object,
       Handle<Map> map,
       Register scratch1,
       Register scratch2,
       SaveFPRegsMode save_fp);
@@ skipping 894 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_MACRO_ASSEMBLER_IA32_H_