Add new HSeqStringGetChar instruction.

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index 2c266d2cd594bdb620086759c8f2779fa9271317..00bfa4eb8378443533c339d68c03da9f8f663e2a 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -1366,6 +1366,15 @@ void Assembler::movb(const Operand& dst, Immediate imm) {
 }
 
 
+void Assembler::movw(Register dst, const Operand& src) {
+  EnsureSpace ensure_space(this);
+  emit(0x66);
+  emit_optional_rex_32(dst, src);
+  emit(0x8B);
+  emit_operand(dst, src);
+}
+
+
 void Assembler::movw(const Operand& dst, Register src) {
   EnsureSpace ensure_space(this);
   emit(0x66);