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 b3047eee6cdce3b5fa149bbb10c1d7c1b56773dd..fe0a94407f38814ac686ca177d86c71627fe5bb8 100644
--- a/src/a64/macro-assembler-a64.h
+++ b/src/a64/macro-assembler-a64.h
@@ -1473,7 +1473,8 @@ class MacroAssembler : public Assembler {
   // Inline caching support.
 
   void EmitSeqStringSetCharCheck(Register string,
-                                 Register index,    // Smi
+                                 Register index,
+                                 Register scratch,

[ulan, 2014/02/06 14:23:43]

This is different from arm port, which takes value register here and doesn't use
it.

                                  uint32_t encoding_mask);
 
   // Generate code for checking access rights - used for security checks