Introduce intrinsics for double values in Javascript.

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 e7784259707cb1a046a8bf221d0ecc404bc131e5..63f0533cd11395f14049e328174bd3c89e8c0b25 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -2798,6 +2798,16 @@ void Assembler::movss(const Operand& src, XMMRegister dst) {
 }
 
 
+void Assembler::psllq(XMMRegister reg, byte imm8) {
+  EnsureSpace ensure_space(this);
+  emit(0x66);
+  emit(0x0F);
+  emit(0x73);
+  emit_sse_operand(rsi, reg);  // rsi == 6
+  emit(imm8);
+}
+
+
 void Assembler::cvttss2si(Register dst, const Operand& src) {
   EnsureSpace ensure_space(this);
   emit(0xF3);