Version 3.5.6.

src/x64/lithium-x64.h

 // 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 2106 matching lines @@
       LInstruction* DefineAsSpilled(LTemplateInstruction<1, I, T>* instr,
                                     int index);
   template<int I, int T>
       LInstruction* DefineSameAsFirst(LTemplateInstruction<1, I, T>* instr);
   template<int I, int T>
       LInstruction* DefineFixed(LTemplateInstruction<1, I, T>* instr,
                                 Register reg);
   template<int I, int T>
       LInstruction* DefineFixedDouble(LTemplateInstruction<1, I, T>* instr,
                                       XMMRegister reg);
+  // Assigns an environment to an instruction.  An instruction which can
+  // deoptimize must have an environment.
   LInstruction* AssignEnvironment(LInstruction* instr);
+  // Assigns a pointer map to an instruction.  An instruction which can
+  // trigger a GC or a lazy deoptimization must have a pointer map.
   LInstruction* AssignPointerMap(LInstruction* instr);
 
   enum CanDeoptimize { CAN_DEOPTIMIZE_EAGERLY, CANNOT_DEOPTIMIZE_EAGERLY };
 
-  // By default we assume that instruction sequences generated for calls
-  // cannot deoptimize eagerly and we do not attach environment to this
-  // instruction.
+  // Marks a call for the register allocator.  Assigns a pointer map to
+  // support GC and lazy deoptimization.  Assigns an environment to support
+  // eager deoptimization if CAN_DEOPTIMIZE_EAGERLY.
   LInstruction* MarkAsCall(
       LInstruction* instr,
       HInstruction* hinstr,
       CanDeoptimize can_deoptimize = CANNOT_DEOPTIMIZE_EAGERLY);
   LInstruction* MarkAsSaveDoubles(LInstruction* instr);
 
   LInstruction* SetInstructionPendingDeoptimizationEnvironment(
       LInstruction* instr, int ast_id);
   void ClearInstructionPendingDeoptimizationEnvironment();
 
@@ skipping 24 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_