dart2js cps: Global value numbering and loop-invariant code motion.

pkg/compiler/lib/src/cps_ir/share_final_fields.dart

Index: pkg/compiler/lib/src/cps_ir/share_final_fields.dart
diff --git a/pkg/compiler/lib/src/cps_ir/share_final_fields.dart b/pkg/compiler/lib/src/cps_ir/share_final_fields.dart
index 3308c00e2407724b41dfa8258a2de89a87eddbf8..d33fb05505e6bed3cb554ea0b4cec9ec962e3338 100644
--- a/pkg/compiler/lib/src/cps_ir/share_final_fields.dart
+++ b/pkg/compiler/lib/src/cps_ir/share_final_fields.dart
@@ -122,8 +122,8 @@ class ShareFinalFields extends TrampolineRecursiveVisitor implements Pass {
       // still in scope and safe (non-null). We will have to replace
       // primitive.object with the most constrained refinement still in scope.
       Continuation referencedLoop =
-          lowestCommonAncestor(loopHeaderFor[refinedReceiver],
-                               currentLoopHeader);
+          loopHierarchy.lowestCommonAncestor(loopHeaderFor[refinedReceiver],
+                                             currentLoopHeader);
       if (referencedLoop != currentLoopHeader) {
         Continuation hoistTarget = getCurrentOuterLoop(scope: referencedLoop);
         LetCont loopBinding = hoistTarget.parent;
@@ -157,25 +157,4 @@ class ShareFinalFields extends TrampolineRecursiveVisitor implements Pass {
     if (backend.isNative(field)) return false;
     return field.isFinal || field.isConst;
   }
-
-  /// Returns the the innermost loop that effectively encloses both
-  /// c1 and c2 (or `null` if there is no such loop).
-  Continuation lowestCommonAncestor(Continuation c1, Continuation c2) {
-    int d1 = getDepth(c1), d2 = getDepth(c2);
-    while (c1 != c2) {
-      if (d1 <= d2) {
-        c2 = loopHierarchy.getEnclosingLoop(c2);
-        d2 = getDepth(c2);
-      } else {
-        c1 = loopHierarchy.getEnclosingLoop(c1);
-        d1 = getDepth(c1);
-      }
-    }
-    return c1;
-  }
-
-  int getDepth(Continuation loop) {
-    if (loop == null) return -1;
-    return loopHierarchy.loopDepth[loop];
-  }
 }