dart2js cps: Use definitions by default, not references.

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

 library dart2js.cps_ir.finalize;
 
 import 'cps_ir_nodes.dart';
 import 'cps_fragment.dart';
 import 'optimizers.dart' show Pass;
 import '../js_backend/js_backend.dart' show JavaScriptBackend;
 import '../js_backend/backend_helpers.dart';
 import '../js/js.dart' as js;
 
 /// A transformation pass that must run immediately before the tree IR builder.
@@ skipping 20 matching lines @@
     return next;
   }
 
   bool areAdjacent(Primitive first, Primitive second) {
     return first.parent == second.parent.parent;
   }
 
   CpsFragment visitBoundsCheck(BoundsCheck node) {
     CpsFragment cps = new CpsFragment(node.sourceInformation);
     if (node.hasNoChecks) {
-      node..replaceUsesWith(node.object.definition)..destroy();
+      node..replaceUsesWith(node.object)..destroy();
       return cps;
     }
     Continuation fail = cps.letCont();
-    Primitive index = node.index.definition;
+    Primitive index = node.index;
     if (node.hasIntegerCheck) {
       cps.ifTruthy(cps.applyBuiltin(BuiltinOperator.IsNotUnsigned32BitInteger,
           [index, index]))
           .invokeContinuation(fail);
     } else if (node.hasLowerBoundCheck) {
       cps.ifTruthy(cps.applyBuiltin(BuiltinOperator.NumLt,
           [index, cps.makeZero()]))
           .invokeContinuation(fail);
     }
     if (node.hasUpperBoundCheck) {
-      Primitive length = node.length.definition;
+      Primitive length = node.length;
       if (length is GetLength &&
           length.hasExactlyOneUse &&
           areAdjacent(length, node)) {
         // Rebind the GetLength here, so it does not get stuck outside the
         // condition, blocked from propagating by the lower bounds check.
         LetPrim lengthBinding = length.parent;
         lengthBinding.remove();
         cps.letPrim(length);
       }
       cps.ifTruthy(cps.applyBuiltin(BuiltinOperator.NumGe,
           [index, length]))
           .invokeContinuation(fail);
     }
     if (node.hasEmptinessCheck) {
       cps.ifTruthy(cps.applyBuiltin(BuiltinOperator.StrictEq,
-          [node.length.definition, cps.makeZero()]))
+          [node.length, cps.makeZero()]))
           .invokeContinuation(fail);
     }
     cps.insideContinuation(fail).invokeStaticThrower(
           helpers.throwIndexOutOfRangeException,
-          [node.object.definition, index]);
-    node..replaceUsesWith(node.object.definition)..destroy();
+          [node.object, index]);
+    node..replaceUsesWith(node.object)..destroy();
     return cps;
   }
 
   void visitGetStatic(GetStatic node) {
-    if (node.witness != null) {
-      node..witness.unlink()..witness = null;
+    if (node.witnessRef != null) {
+      node..witnessRef.unlink()..witnessRef = null;
     }
   }
 
   void visitForeignCode(ForeignCode node) {
     if (js.isIdentityTemplate(node.codeTemplate)) {
       // The CPS builder replaces identity templates with refinements, except
       // when the refined type is an array type.  Some optimizations assume the
       // type of an object is immutable, but the type of an array can change
       // after allocation.  After the finalize pass, this assumption is no
       // longer needed, so we can replace the remaining idenitity templates.
-      Refinement refinement = new Refinement(
-          node.arguments.single.definition,
-          node.type)..type = node.type;
+      Refinement refinement = new Refinement(node.argument(0), node.type)
+          ..type = node.type;
       node.replaceWith(refinement);
     }
   }
 }