Use cmov instructions to avoid some conditional branches in stub code....

src/x64/codegen-x64.cc

 // Copyright 2009 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 6580 matching lines @@
   __ TailCallRuntime(ExternalReference(f), 1, f->result_size);
 }
 
 
 void ArgumentsAccessStub::GenerateReadLength(MacroAssembler* masm) {
   // Check if the calling frame is an arguments adaptor frame.
   Label adaptor;
   __ movq(rdx, Operand(rbp, StandardFrameConstants::kCallerFPOffset));
   __ SmiCompare(Operand(rdx, StandardFrameConstants::kContextOffset),
                 Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
-  __ j(equal, &adaptor);
-
-  // Nothing to do: The formal number of parameters has already been
-  // passed in register rax by calling function. Just return it.
-  __ ret(0);
 
   // Arguments adaptor case: Read the arguments length from the
   // adaptor frame and return it.
-  __ bind(&adaptor);
-  __ movq(rax, Operand(rdx, ArgumentsAdaptorFrameConstants::kLengthOffset));
+  // Otherwise nothing to do: The number of formal parameters has already been
+  // passed in register eax by calling function. Just return it.
+  __ cmovq(equal, rax,
+           Operand(rdx, ArgumentsAdaptorFrameConstants::kLengthOffset));
   __ ret(0);
 }
 
 
 int CEntryStub::MinorKey() {
   ASSERT(result_size_ <= 2);
 #ifdef _WIN64
   // Simple results returned in rax (using default code).
   // Complex results must be written to address passed as first argument.
   // Use even numbers for minor keys, reserving the odd numbers for
@@ skipping 1423 matching lines @@
   masm.GetCode(&desc);
   // Call the function from C++.
   return FUNCTION_CAST<ModuloFunction>(buffer);
 }
 
 #endif
 
 #undef __
 
 } }  // namespace v8::internal