ia32 StringAddStub: fast two character case.

src/ia32/code-stubs-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
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 //       disclaimer in the documentation and/or other materials provided
@@ skipping 216 matching lines @@
   // Generate code for copying characters using the rep movs instruction.
   // Copies ecx characters from esi to edi. Copying of overlapping regions is
   // not supported.
   static void GenerateCopyCharactersREP(MacroAssembler* masm,
                                         Register dest,     // Must be edi.
                                         Register src,      // Must be esi.
                                         Register count,    // Must be ecx.
                                         Register scratch,  // Neither of above.
                                         bool ascii);
 
-  // Probe the symbol table for a two character string. If the string is
-  // not found by probing a jump to the label not_found is performed. This jump
-  // does not guarantee that the string is not in the symbol table. If the
-  // string is found the code falls through with the string in register eax.
+  // Probe the symbol table for a two character string. If the string
+  // requires non-standard hashing a jump to the label not_probed is
+  // performed and registers c1 and c2 are preserved. If the string is
+  // not found by probing a jump to the label not_found is
+  // performed. This jump does not guarantee that the string is not in

[Søren Thygesen Gjesse, 2010/09/01 11:19:31]

Maybe extend the comment to say that c1 and c2 are clobbered when a jump to
not_found is performed.

[Vitaly Repeshko, 2010/09/01 17:21:51]

Done.

+  // the symbol table. If the string is found the code falls through
+  // with the string in register eax.
   static void GenerateTwoCharacterSymbolTableProbe(MacroAssembler* masm,
                                                    Register c1,
                                                    Register c2,
                                                    Register scratch1,
                                                    Register scratch2,
                                                    Register scratch3,
+                                                   Label* not_probed,

[Søren Thygesen Gjesse, 2010/09/01 11:19:31]

How about renaming not_probed to not_found_c1_c2_preserved? Maybe not?

[Vitaly Repeshko, 2010/09/01 17:21:51]

I think having this described in the comment is enough.

                                                    Label* not_found);
 
   // Generate string hash.
   static void GenerateHashInit(MacroAssembler* masm,
                                Register hash,
                                Register character,
                                Register scratch);
   static void GenerateHashAddCharacter(MacroAssembler* masm,
                                        Register hash,
                                        Register character,
@@ skipping 94 matching lines @@
   void Print() {
     PrintF("NumberToStringStub\n");
   }
 #endif
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_CODE_STUBS_IA32_H_