A64: Port LSeqStringSetChar optimizations from r16707 and r17521.

src/a64/macro-assembler-a64.h

Index: src/a64/macro-assembler-a64.h
diff --git a/src/a64/macro-assembler-a64.h b/src/a64/macro-assembler-a64.h
index b8db68a7daab946348cea6bdce7eb71444fcd4a9..7acce66f0649578dc828785c4d92437f613f131a 100644
--- a/src/a64/macro-assembler-a64.h
+++ b/src/a64/macro-assembler-a64.h
@@ -1475,7 +1475,9 @@ class MacroAssembler : public Assembler {
   // Inline caching support.
 
   void EmitSeqStringSetCharCheck(Register string,
-                                 Register index,    // Smi
+                                 Register index,
+                                 bool index_is_smi,

[baptiste.afsa1, 2014/02/06 15:48:13]

Usually v8 functions which use that kind of trick use an enum to specify the
"mode" instead of a bool. Maybe you should do the same here.

[ulan, 2014/02/06 16:06:14]

Done.

+                                 Register scratch,
                                  uint32_t encoding_mask);
 
   // Generate code for checking access rights - used for security checks