Ported SubStringStub to X64.

src/x64/codegen-x64.h

 // 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 695 matching lines @@
   }
 
   void SetArgsInRegisters() { args_in_registers_ = true; }
   void SetArgsReversed() { args_reversed_ = true; }
   bool HasSmiCodeInStub() { return (flags_ & NO_SMI_CODE_IN_STUB) == 0; }
   bool HasArgumentsInRegisters() { return args_in_registers_; }
   bool HasArgumentsReversed() { return args_reversed_; }
 };
 
 
+class StringStubBase: public CodeStub {
+ public:
+  // Generate code for copying characters using a simple loop. This should only
+  // be used in places where the number of characters is small and the
+  // additional setup and checking in GenerateCopyCharactersREP adds too much
+  // overhead. Copying of overlapping regions is not supported.
+  void GenerateCopyCharacters(MacroAssembler* masm,
+                              Register dest,
+                              Register src,
+                              Register count,
+                              bool ascii);
+
+  // Generate code for copying characters using the rep movs instruction.
+  // Copies rcx characters from rsi to rdi. Copying of overlapping regions is
+  // not supported.
+  void GenerateCopyCharactersREP(MacroAssembler* masm,
+                                 Register dest,     // Must be rdi.
+                                 Register src,      // Must be rsi.
+                                 Register count,    // Must be rcx.
+                                 bool ascii);
+};
+
+
 // Flag that indicates how to generate code for the stub StringAddStub.
 enum StringAddFlags {
   NO_STRING_ADD_FLAGS = 0,
   NO_STRING_CHECK_IN_STUB = 1 << 0  // Omit string check in stub.
 };
 
 
-class StringAddStub: public CodeStub {
+class StringAddStub: public StringStubBase {
  public:
   explicit StringAddStub(StringAddFlags flags) {
     string_check_ = ((flags & NO_STRING_CHECK_IN_STUB) == 0);
   }
 
  private:
   Major MajorKey() { return StringAdd; }
   int MinorKey() { return string_check_ ? 0 : 1; }
 
   void Generate(MacroAssembler* masm);
 
-  void GenerateCopyCharacters(MacroAssembler* masm,
-                              Register desc,
-                              Register src,
-                              Register count,
-                              bool ascii);
-
   // Should the stub check whether arguments are strings?
   bool string_check_;
 };
 
 
+class SubStringStub: public StringStubBase {
+ public:
+  SubStringStub() {}
+
+ private:
+  Major MajorKey() { return SubString; }
+  int MinorKey() { return 0; }
+
+  void Generate(MacroAssembler* masm);
+};
+
+
 class StringCompareStub: public CodeStub {
  public:
   explicit StringCompareStub() {}
 
   // Compare two flat ascii strings and returns result in rax after popping two
   // arguments from the stack.
   static void GenerateCompareFlatAsciiStrings(MacroAssembler* masm,
                                               Register left,
                                               Register right,
                                               Register scratch1,
                                               Register scratch2,
                                               Register scratch3,
                                               Register scratch4);
 
  private:
   Major MajorKey() { return StringCompare; }
   int MinorKey() { return 0; }
 
   void Generate(MacroAssembler* masm);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_CODEGEN_X64_H_