Version 3.5.6.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index ff756e0b5bdf7aee0290d7f2b64a46233aa73508..b570672f682e0abcffaa7713f6fa0f0799ec627a 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -2124,14 +2124,18 @@ class LChunkBuilder BASE_EMBEDDED {
   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,