Avoid a smi check when comparing an unknown to a constant smi for equality on...

src/x64/codegen-x64.h

 // Copyright 2010 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 503 matching lines @@
   // Consumes the Results *left and *right.
   Result LikelySmiBinaryOperation(BinaryOperation* expr,
                                   Result* left,
                                   Result* right,
                                   OverwriteMode overwrite_mode);
 
   void Comparison(AstNode* node,
                   Condition cc,
                   bool strict,
                   ControlDestination* destination);
+
+  // If at least one of the sides is a constant smi, generate optimized code.
+  void ConstantSmiComparison(Condition cc,
+                             bool strict,
+                             ControlDestination* destination,
+                             Result* left_side,
+                             Result* right_side,
+                             bool left_side_constant_smi,
+                             bool right_side_constant_smi,
+                             bool is_loop_condition);
+
   void GenerateInlineNumberComparison(Result* left_side,
                                       Result* right_side,
                                       Condition cc,
                                       ControlDestination* dest);
 
   // To prevent long attacker-controlled byte sequences, integer constants
   // from the JavaScript source are loaded in two parts if they are larger
   // than 16 bits.
   static const int kMaxSmiInlinedBits = 16;
   bool IsUnsafeSmi(Handle<Object> value);
@@ skipping 516 matching lines @@
     return ObjectBits::encode(object_.code()) |
            AddressBits::encode(addr_.code()) |
            ScratchBits::encode(scratch_.code());
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_CODEGEN_X64_H_