Introduce intrinsics for double values in Javascript.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 3724cff8df904fafdf82fbfbf628256e241f444b..3f2f0214f684a7771e90731a4f665ab79556fd85 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -80,12 +80,14 @@ 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(DoubleToI)                                  \
   V(DoubleToSmi)                                \
   V(Drop)                                       \
@@ -2313,6 +2315,33 @@ class LCheckNonSmi V8_FINAL : public LTemplateInstruction<0, 1, 0> {
 };
 
 
+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, 0> {
+ public:
+  LConstructDouble(LOperand* hi, LOperand* lo) {
+    inputs_[0] = hi;
+    inputs_[1] = lo;
+  }
+
+  LOperand* hi() { return inputs_[0]; }
+  LOperand* lo() { return inputs_[1]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(ConstructDouble, "construct-double")
+};
+
+
 class LAllocate V8_FINAL : public LTemplateInstruction<1, 2, 1> {
  public:
   LAllocate(LOperand* context, LOperand* size, LOperand* temp) {