Revert "dart2js cps: Add helpers for common IR manipulation."

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

Index: pkg/compiler/lib/src/cps_ir/redundant_phi.dart
diff --git a/pkg/compiler/lib/src/cps_ir/redundant_phi.dart b/pkg/compiler/lib/src/cps_ir/redundant_phi.dart
index ae57325dff142de9c48634b8f72fb5ecd28aa61c..e678a968efcf9fee1f8ba667aa715a210a08d24f 100644
--- a/pkg/compiler/lib/src/cps_ir/redundant_phi.dart
+++ b/pkg/compiler/lib/src/cps_ir/redundant_phi.dart
@@ -187,9 +187,19 @@ bool _isInScopeOf(LetCont letCont, Definition definition) {
 void _moveIntoScopeOf(LetCont letCont, Definition definition) {
   if (_isInScopeOf(letCont, definition)) return;
 
+  // Remove the continuation binding from its current spot.
+  InteriorNode parent = letCont.parent;
+  parent.body = letCont.body;
+  letCont.body.parent = parent;
+
+  // Insert it just below the binding of definition.
   InteriorNode binding = definition.parent;
-  letCont.remove();
-  letCont.insertBelow(binding);
+
+  letCont.body = binding.body;
+  binding.body.parent = letCont;
+
+  binding.body = letCont;
+  letCont.parent = binding;
 }
 
 /// Ensures [continuation] has its own LetCont binding by creating
@@ -201,7 +211,9 @@ LetCont _makeUniqueBinding(Continuation continuation) {
   if (letCont.continuations.length == 1) return letCont;
   letCont.continuations.remove(continuation);
   LetCont newBinding = new LetCont(continuation, letCont.body);
+  newBinding.body.parent = newBinding;
+  newBinding.parent = letCont;
+  letCont.body = newBinding;
   continuation.parent = newBinding;
-  newBinding.insertBelow(letCont);
   return newBinding;
 }