SSI implementation.

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index 0837bf9634e33cc088a7a8dea90e479161c65902..236369ce64a11ae539113bcc2eb5c5a20b005867 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -161,6 +161,29 @@ class HBasicBlock: public ZoneObject {
 
   inline Zone* zone() const;
 
+  void BuildSsiRecursively() {
+    BuildSsi();
+    for (int i = 0; i < dominated_blocks()->length(); ++i) {
+      dominated_blocks()->at(i)->BuildSsiRecursively();
+    }
+  }
+  void BuildSsi() {
+    for (int i = 0; i < phis()->length(); i++) {
+      HPhi* current = phis()->at(i);
+      current->SetFlag(HValue::kProcessedBySsi);
+      current->BuildSsi();
+    }
+
+    for (HInstruction* current = first();
+        current != NULL;
+        current = current->next()) {
+      // We set the flag before calling BuildSsi so that, while creating new
+      // SSI definitions, uses inside current will not be updated.
+      current->SetFlag(HValue::kProcessedBySsi);
+      current->BuildSsi();
+    }
+  }
+
 #ifdef DEBUG
   void Verify();
 #endif
@@ -290,6 +313,7 @@ class HGraph: public ZoneObject {
     undefined_constant_.set(constant);
   }
   HConstant* GetConstantUndefined() const { return undefined_constant_.get(); }
+  HConstant* GetConstant0();
   HConstant* GetConstant1();
   HConstant* GetConstantMinus1();
   HConstant* GetConstantTrue();
@@ -370,6 +394,9 @@ class HGraph: public ZoneObject {
     uint32_instructions_->Add(instr, zone());
   }
 
+  void BuildSsi();
+  void CleanupSsi();
+
  private:
   HConstant* GetConstant(SetOncePointer<HConstant>* pointer,
                          Handle<Object> value);
@@ -399,6 +426,7 @@ class HGraph: public ZoneObject {
   ZoneList<HPhi*>* phi_list_;
   ZoneList<HInstruction*>* uint32_instructions_;
   SetOncePointer<HConstant> undefined_constant_;
+  SetOncePointer<HConstant> constant_0_;
   SetOncePointer<HConstant> constant_1_;
   SetOncePointer<HConstant> constant_minus1_;
   SetOncePointer<HConstant> constant_true_;