Speed up FastAsciiArrayJoin on ia32 by improving hand-written assembly code.

src/ia32/macro-assembler-ia32.h

 // Copyright 2010 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 368 matching lines @@
   // initialized.
   void AllocateConsString(Register result,
                           Register scratch1,
                           Register scratch2,
                           Label* gc_required);
   void AllocateAsciiConsString(Register result,
                                Register scratch1,
                                Register scratch2,
                                Label* gc_required);
 
-  // All registers must be distinct.  Only current_string needs valid contents
-  // on entry.  All registers may be invalid on exit.  result_operand is
-  // unchanged, padding_chars is updated correctly.
-  // The top of new space must contain a sequential ascii string with
-  // padding_chars bytes free in its top word.  The sequential ascii string
-  // current_string is concatenated to it, allocating the necessary amount
-  // of new memory.
-  void AppendStringToTopOfNewSpace(
-      Register current_string,  // Tagged pointer to string to copy.
-      Register current_string_length,
-      Register result_pos,
-      Register scratch,
-      Register new_padding_chars,
-      Operand operand_result,
-      Operand operand_padding_chars,
-      Label* bailout);
+  // Copy memory, byte-by-byte, from source to destination.  Not optimized for
+  // long or aligned copies.
+  // The contents of index and scratch are destroyed.
+  void CopyBytes(Register source,
+                 Register destination,
+                 Register length,
+                 Register scratch);
 
   // ---------------------------------------------------------------------------
   // Support functions.
 
   // Check if result is zero and op is negative.
   void NegativeZeroTest(Register result, Register op, Label* then_label);
 
   // Check if result is zero and op is negative in code using jump targets.
   void NegativeZeroTest(CodeGenerator* cgen,
                         Register result,
@@ skipping 350 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_MACRO_ASSEMBLER_IA32_H_