Introduce intrinsics for double values in Javascript.

src/a64/lithium-a64.h

Index: src/a64/lithium-a64.h
diff --git a/src/a64/lithium-a64.h b/src/a64/lithium-a64.h
index 26234e92429f0fadfc0eb64b32cefd5ec253acc2..fed928035415a3173dee2b5984c429c98e51a260 100644
--- a/src/a64/lithium-a64.h
+++ b/src/a64/lithium-a64.h
@@ -84,12 +84,14 @@ class LCodeGen;
   V(ConstantI)                                  \
   V(ConstantS)                                  \
   V(ConstantT)                                  \
+  V(ConstructDouble)                            \
   V(Context)                                    \
   V(DateField)                                  \
   V(DebugBreak)                                 \
   V(DeclareGlobals)                             \
   V(Deoptimize)                                 \
   V(DivI)                                       \
+  V(DoubleBits)                                 \
   V(DoubleToIntOrSmi)                           \
   V(Drop)                                       \
   V(Dummy)                                      \
@@ -1011,6 +1013,35 @@ class LClampTToUint8 V8_FINAL : public LTemplateInstruction<1, 1, 2> {
 };
 
 
+class LDoubleBits V8_FINAL : public LTemplateInstruction<1, 1, 0> {
+ public:
+  explicit LDoubleBits(LOperand* value) {
+    inputs_[0] = value;
+  }
+
+  LOperand* value() { return inputs_[0]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(DoubleBits, "double-bits")
+  DECLARE_HYDROGEN_ACCESSOR(DoubleBits)
+};
+
+
+class LConstructDouble V8_FINAL : public LTemplateInstruction<1, 2, 1> {
+ public:
+  LConstructDouble(LOperand* hi, LOperand* lo, LOperand* temp) {
+    inputs_[0] = hi;
+    inputs_[1] = lo;
+    temps_[0] = temp;
+  }
+
+  LOperand* hi() { return inputs_[0]; }
+  LOperand* lo() { return inputs_[1]; }
+  LOperand* temp() { return temps_[0]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(ConstructDouble, "construct-double")
+};
+
+
 class LClassOfTestAndBranch V8_FINAL : public LControlInstruction<1, 2> {
  public:
   LClassOfTestAndBranch(LOperand* value, LOperand* temp1, LOperand* temp2) {