Cosmetic changes ("set up" is a verb, "setup" is a noun).

src/x64/macro-assembler-x64.h

 // 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 310 matching lines @@
   void InitializeRootRegister() {
     ExternalReference roots_array_start =
         ExternalReference::roots_array_start(isolate());
     movq(kRootRegister, roots_array_start);
     addq(kRootRegister, Immediate(kRootRegisterBias));
   }
 
   // ---------------------------------------------------------------------------
   // JavaScript invokes
 
-  // Setup call kind marking in rcx. The method takes rcx as an
+  // Set up call kind marking in rcx. The method takes rcx as an
   // explicit first parameter to make the code more readable at the
   // call sites.
   void SetCallKind(Register dst, CallKind kind);
 
   // Invoke the JavaScript function code by either calling or jumping.
   void InvokeCode(Register code,
                   const ParameterCount& expected,
                   const ParameterCount& actual,
                   InvokeFlag flag,
                   const CallWrapper& call_wrapper,
@@ skipping 1106 matching lines @@
     masm->popfd();                                                        \
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_