ia32 StringAddStub: fast two character case.

src/ia32/code-stubs-ia32.h

Index: src/ia32/code-stubs-ia32.h
diff --git a/src/ia32/code-stubs-ia32.h b/src/ia32/code-stubs-ia32.h
index acf4a6f94879968fc4629389f7f2d756383e844d..82d812f08b642108f38370a7b5a1a182304e2ebf 100644
--- a/src/ia32/code-stubs-ia32.h
+++ b/src/ia32/code-stubs-ia32.h
@@ -234,16 +234,20 @@ class StringHelper : public AllStatic {
                                         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.