Introduce intrinsics for double values in Javascript.

src/a64/lithium-codegen-a64.cc

Index: src/a64/lithium-codegen-a64.cc
diff --git a/src/a64/lithium-codegen-a64.cc b/src/a64/lithium-codegen-a64.cc
index fea4db7ffd9ae7418c297ce9680979e8e391aed8..c0bd142dd1bae4e74981d195b0f236851a1dbfda 100644
--- a/src/a64/lithium-codegen-a64.cc
+++ b/src/a64/lithium-codegen-a64.cc
@@ -2231,6 +2231,30 @@ void LCodeGen::DoClampTToUint8(LClampTToUint8* instr) {
 }
 
 
+void LCodeGen::DoDoubleBits(LDoubleBits* instr) {
+  DoubleRegister value_reg = ToDoubleRegister(instr->value());
+  Register result_reg = ToRegister(instr->result());
+  if (instr->hydrogen()->bits() == HDoubleBits::HIGH) {
+    __ Fmov(result_reg, value_reg);
+    __ Mov(result_reg, Operand(result_reg, LSR, 32));
+  } else {
+    __ Fmov(result_reg.W(), value_reg.S());
+  }
+}
+
+
+void LCodeGen::DoConstructDouble(LConstructDouble* instr) {
+  Register hi_reg = ToRegister(instr->hi());
+  Register lo_reg = ToRegister(instr->lo());
+  Register temp = ToRegister(instr->temp());
+  DoubleRegister result_reg = ToDoubleRegister(instr->result());
+
+  __ And(temp, lo_reg, Operand(0xffffffff));
+  __ Orr(temp, temp, Operand(hi_reg, LSL, 32));
+  __ Fmov(result_reg, temp);
+}
+
+
 void LCodeGen::DoClassOfTestAndBranch(LClassOfTestAndBranch* instr) {
   Handle<String> class_name = instr->hydrogen()->class_name();
   Label* true_label = instr->TrueLabel(chunk_);