Remove write barriers for cells on x64, ARM and MIPS.

src/x64/lithium-codegen-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2029 matching lines @@
   // been deleted from the property dictionary. In that case, we need
   // to update the property details in the property dictionary to mark
   // it as no longer deleted. We deoptimize in that case.
   if (instr->hydrogen()->RequiresHoleCheck()) {
     __ CompareRoot(Operand(address, 0), Heap::kTheHoleValueRootIndex);
     DeoptimizeIf(equal, instr->environment());
   }
 
   // Store the value.
   __ movq(Operand(address, 0), value);
-
-  if (instr->hydrogen()->NeedsWriteBarrier()) {
-    Label smi_store;
-    HType type = instr->hydrogen()->value()->type();
-    if (!type.IsHeapNumber() && !type.IsString() && !type.IsNonPrimitive()) {
-      __ JumpIfSmi(value, &smi_store, Label::kNear);
-    }
-
-    int offset = JSGlobalPropertyCell::kValueOffset - kHeapObjectTag;
-    __ lea(object, Operand(address, -offset));
-    // Cells are always in the remembered set.
-    __ RecordWrite(object,
-                   address,
-                   value,
-                   kSaveFPRegs,
-                   OMIT_REMEMBERED_SET,
-                   OMIT_SMI_CHECK);
-    __ bind(&smi_store);
-  }
+  // Cells are always rescanned, so no write barrier here.
 }
 
 
 void LCodeGen::DoStoreGlobalGeneric(LStoreGlobalGeneric* instr) {
   ASSERT(ToRegister(instr->global_object()).is(rdx));
   ASSERT(ToRegister(instr->value()).is(rax));
 
   __ Move(rcx, instr->name());
   Handle<Code> ic = (instr->strict_mode_flag() == kStrictMode)
       ? isolate()->builtins()->StoreIC_Initialize_Strict()
@@ skipping 2247 matching lines @@
   RegisterEnvironmentForDeoptimization(environment, Safepoint::kNoLazyDeopt);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64