diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 1ee0fe0..4c17720 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -74,7 +74,11 @@
 // MacroAssembler implements a collection of frequently used macros.
 class MacroAssembler: public Assembler {
  public:
-  MacroAssembler(void* buffer, int size);
+  // The isolate parameter can be NULL if the macro assembler should
+  // not use isolate-dependent functionality. In this case, it's the
+  // responsibility of the caller to never invoke such function on the
+  // macro assembler.
+  MacroAssembler(Isolate* isolate, void* buffer, int size);
 
   // Prevent the use of the RootArray during the lifetime of this
   // scope object.
@@ -319,6 +323,16 @@
                                            Register src,
                                            int power);
 
+  // Perform the logical or of two smi values and return a smi value.
+  // If either argument is not a smi, jump to on_not_smis and retain
+  // the original values of source registers. The destination register
+  // may be changed if it's not one of the source registers.
+  template <typename LabelType>
+  void SmiOrIfSmis(Register dst,
+                   Register src1,
+                   Register src2,
+                   LabelType* on_not_smis);
+
 
   // Simple comparison of smis.  Both sides must be known smis to use these,
   // otherwise use Cmp.
@@ -1029,7 +1043,10 @@
   // may be bigger than 2^16 - 1.  Requires a scratch register.
   void Ret(int bytes_dropped, Register scratch);
 
-  Handle<Object> CodeObject() { return code_object_; }
+  Handle<Object> CodeObject() {
+    ASSERT(!code_object_.is_null());
+    return code_object_;
+  }
 
   // Copy length bytes from source to destination.
   // Uses scratch register internally (if you have a low-eight register
@@ -1076,6 +1093,10 @@
   void set_allow_stub_calls(bool value) { allow_stub_calls_ = value; }
   bool allow_stub_calls() { return allow_stub_calls_; }
 
+  static int SafepointRegisterStackIndex(Register reg) {
+    return SafepointRegisterStackIndex(reg.code());
+  }
+
  private:
   // Order general registers are pushed by Pushad.
   // rax, rcx, rdx, rbx, rsi, rdi, r8, r9, r11, r14, r15.
@@ -1779,6 +1800,24 @@
 
 
 template <typename LabelType>
+void MacroAssembler::SmiOrIfSmis(Register dst, Register src1, Register src2,
+                                 LabelType* on_not_smis) {
+  if (dst.is(src1) || dst.is(src2)) {
+    ASSERT(!src1.is(kScratchRegister));
+    ASSERT(!src2.is(kScratchRegister));
+    movq(kScratchRegister, src1);
+    or_(kScratchRegister, src2);
+    JumpIfNotSmi(kScratchRegister, on_not_smis);
+    movq(dst, kScratchRegister);
+  } else {
+    movq(dst, src1);
+    or_(dst, src2);
+    JumpIfNotSmi(dst, on_not_smis);
+  }
+}
+
+
+template <typename LabelType>
 void MacroAssembler::JumpIfNotString(Register object,
                                      Register object_map,
                                      LabelType* not_string) {