Re-use phi reachability information to avoid a fixed-point computation.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h	(revision 9206)
+++ src/hydrogen-instructions.h	(working copy)
@@ -2209,6 +2209,13 @@
     is_convertible_to_integer_ = b;
   }
 
+  bool AllOperandsConvertibleToInteger() {
+    for (int i = 0; i < OperandCount(); ++i) {
+      if (!OperandAt(i)->IsConvertibleToInteger()) return false;
+    }
+    return true;
+  }
+
  protected:
   virtual void DeleteFromGraph();
   virtual void InternalSetOperandAt(int index, HValue* value) {