Improve implementation of HSeqStringSetChar.

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 dcb9fa562159b8e33f2cfff8b7ffcf205c57b77e..5da18dd3a1f107a489cc325070c0e3d551491cf7 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -1357,6 +1357,15 @@ void Assembler::movb(const Operand& dst, Register src) {
 }
 
 
+void Assembler::movb(const Operand& dst, Immediate imm) {
+  EnsureSpace ensure_space(this);
+  emit_optional_rex_32(dst);
+  emit(0xC6);
+  emit_operand(0x0, dst);
+  emit(static_cast<byte>(imm.value_));
+}
+
+
 void Assembler::movw(const Operand& dst, Register src) {
   EnsureSpace ensure_space(this);
   emit(0x66);
@@ -1366,6 +1375,17 @@ void Assembler::movw(const Operand& dst, Register src) {
 }
 
 
+void Assembler::movw(const Operand& dst, Immediate imm) {
+  EnsureSpace ensure_space(this);
+  emit(0x66);
+  emit_optional_rex_32(dst);
+  emit(0xC7);
+  emit_operand(0x0, dst);
+  emit(static_cast<byte>(imm.value_ & 0xff));
+  emit(static_cast<byte>(imm.value_ >> 8));
+}
+
+
 void Assembler::movl(Register dst, const Operand& src) {
   EnsureSpace ensure_space(this);
   emit_optional_rex_32(dst, src);