Add support for adding an external and a tagged pointer

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 11e85a0c034ab6a689eaa4fdf55cb537f9af1035..68b84c1749fda629ea1ae1df4c75d47f4fac3473 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -4830,11 +4830,21 @@ class HPower final : public HTemplateInstruction<2> {
 };
 
 
+enum ExternalAddType {
+  AddOfExternalAndTagged,
+  AddOfExternalAndInt32,
+  NoExternalAdd
+};
+
+
 class HAdd final : public HArithmeticBinaryOperation {
  public:
   static HInstruction* New(Isolate* isolate, Zone* zone, HValue* context,
                            HValue* left, HValue* right,
                            Strength strength = Strength::WEAK);
+  static HInstruction* New(Isolate* isolate, Zone* zone, HValue* context,
+                           HValue* left, HValue* right, Strength strength,
+                           ExternalAddType external_add_type);
 
   // Add is only commutative if two integer values are added and not if two
   // tagged values are added (because it might be a String concatenation).
@@ -4877,6 +4887,8 @@ class HAdd final : public HArithmeticBinaryOperation {
 
   Representation RequiredInputRepresentation(int index) override;
 
+  ExternalAddType external_add_type() const { return external_add_type_; }
+
   DECLARE_CONCRETE_INSTRUCTION(Add)
 
  protected:
@@ -4885,10 +4897,28 @@ class HAdd final : public HArithmeticBinaryOperation {
   Range* InferRange(Zone* zone) override;
 
  private:
-  HAdd(HValue* context, HValue* left, HValue* right, Strength strength)
-      : HArithmeticBinaryOperation(context, left, right, strength) {
+  HAdd(HValue* context, HValue* left, HValue* right, Strength strength,
+       ExternalAddType external_add_type = NoExternalAdd)
+      : HArithmeticBinaryOperation(context, left, right, strength),
+        external_add_type_(external_add_type) {
     SetFlag(kCanOverflow);
+    if (left->representation().IsExternal()) {
+      if (right->representation().IsTagged()) {
+        DCHECK_EQ(external_add_type_, AddOfExternalAndTagged);
+        SetDependsOnFlag(kNewSpacePromotion);
+      } else {
+        // This is a bit of a hack: The call to this constructor is generated
+        // by a macro that also supports sub and mul, so it doesn't pass in
+        // a value for external_add_type but uses the default.
+        DCHECK_EQ(external_add_type_, NoExternalAdd);
+        external_add_type_ = AddOfExternalAndInt32;
+      }
+    } else {
+      DCHECK_EQ(external_add_type_, NoExternalAdd);
+    }

[Jarin, 2015/07/20 14:17:56]

Hmm, I was imagining you would drive it the other way:

if (external_add_type == AddOfExternalAndTagged) {
  DCHECK(left->representation().IsExternal());
  DCHECK(right->representation().IsTagged());
  SetDependsOnFlag(kNewSpacePromotion);
} else {
  ...
}

   }
+
+  ExternalAddType external_add_type_;
 };