Smi immediates are not supported on x64. Do not use it.

src/x64/lithium-x64.cc

 // Copyright 2012 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 1514 matching lines @@
   if (instr->representation().IsSmiOrInteger32()) {
     // Check to see if it would be advantageous to use an lea instruction rather
     // than an add. This is the case when no overflow check is needed and there
     // are multiple uses of the add's inputs, so using a 3-register add will
     // preserve all input values for later uses.
     bool use_lea = LAddI::UseLea(instr);
     ASSERT(instr->left()->representation().Equals(instr->representation()));
     ASSERT(instr->right()->representation().Equals(instr->representation()));
     LOperand* left = UseRegisterAtStart(instr->BetterLeftOperand());
     HValue* right_candidate = instr->BetterRightOperand();
-    LOperand* right = use_lea
-        ? UseRegisterOrConstantAtStart(right_candidate)
-        : UseOrConstantAtStart(right_candidate);
+    LOperand* right;
+    if (instr->representation().IsSmi()) {
+      // We cannot add a tagged immediate to a tagged value,
+      // so we request it in a register.
+      right = UseRegisterAtStart(right_candidate);
+    } else {
+      right = use_lea ? UseRegisterOrConstantAtStart(right_candidate)
+                      : UseOrConstantAtStart(right_candidate);
+    }
     LAddI* add = new(zone()) LAddI(left, right);
     bool can_overflow = instr->CheckFlag(HValue::kCanOverflow);
-    LInstruction* result = use_lea
-        ? DefineAsRegister(add)
-        : DefineSameAsFirst(add);
+    LInstruction* result = use_lea ? DefineAsRegister(add)
+                                   : DefineSameAsFirst(add);
     if (can_overflow) {
       result = AssignEnvironment(result);
     }
     return result;
   } else if (instr->representation().IsExternal()) {
     ASSERT(instr->left()->representation().IsExternal());
     ASSERT(instr->right()->representation().IsInteger32());
     ASSERT(!instr->CheckFlag(HValue::kCanOverflow));
     bool use_lea = LAddI::UseLea(instr);
     LOperand* left = UseRegisterAtStart(instr->left());
@@ skipping 1045 matching lines @@
   LOperand* index = UseTempRegister(instr->index());
   LLoadFieldByIndex* load = new(zone()) LLoadFieldByIndex(object, index);
   LInstruction* result = DefineSameAsFirst(load);
   return AssignPointerMap(result);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64