dart2js cps: Debugging utility and fix idempotency in shrinking reducer.

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

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.ir_tracer;
 
 import 'dart:async' show EventSink;
 import 'cps_ir_nodes.dart' as cps_ir;
 import '../tracer.dart';
 
@@ skipping 11 matching lines @@
 
   void traceGraph(String name, cps_ir.FunctionDefinition node) {
     tag("cfg", () {
       printProperty("name", name);
 
       names = new Names();
       BlockCollector builder = new BlockCollector(names);
       builder.visit(node);
 
       for (Block block in builder.entries) {
-        printBlock(block, entryPointParameters: node.parameters);
+        printBlock(block, entryPoint: node);
       }
       for (Block block in builder.cont2block.values) {
         printBlock(block);
       }
       names = null;
     });
   }
 
   // Temporary field used during tree walk
   Names names;
@@ skipping 13 matching lines @@
   int countUses(cps_ir.Definition definition) {
     int count = 0;
     cps_ir.Reference ref = definition.firstRef;
     while (ref != null) {
       ++count;
       ref = ref.next;
     }
     return count;
   }
 
-  /// If [entryPointParameters] is given, this block is an entry point
-  /// and [entryPointParameters] is the list of function parameters.
-  printBlock(Block block, {List<cps_ir.Definition> entryPointParameters}) {
+  /// If [entryPoint] is given, this block is an entry point.
+  printBlock(Block block, {cps_ir.FunctionDefinition entryPoint}) {
     tag("block", () {
       printProperty("name", block.name);
       printProperty("from_bci", -1);
       printProperty("to_bci", -1);
       printProperty("predecessors", block.pred.map((n) => n.name));
       printProperty("successors", block.succ.map((n) => n.name));
       printEmptyProperty("xhandlers");
       printEmptyProperty("flags");
       tag("states", () {
         tag("locals", () {
           printProperty("size", 0);
           printProperty("method", "None");
         });
       });
       tag("HIR", () {
         String formatParameter(cps_ir.Parameter param) {
           return '${names.name(param)} ${param.type}';
         }
-        if (entryPointParameters != null) {
-          String params = entryPointParameters.map(formatParameter).join(', ');
-          printStmt('x0', 'Entry ($params)');
+        if (entryPoint != null) {
+          String thisParam = entryPoint.thisParameter != null
+              ? formatParameter(entryPoint.thisParameter)
+              : 'no receiver';
+          String params = entryPoint.parameters.map(formatParameter).join(', ');
+          printStmt('x0', 'Entry ($thisParam) ($params)');
         }
         String params = block.parameters.map(formatParameter).join(', ');
         printStmt('x0', 'Parameters ($params)');
         visit(block.body);
       });
     });
   }
 
   void printStmt(String resultVar, String contents) {
     int bci = 0;
@@ skipping 577 matching lines @@
   }
 
   visitBoundsCheck(cps_ir.BoundsCheck node) {
     unexpectedNode(node);
   }
 
   visitNullCheck(cps_ir.NullCheck node) {
     unexpectedNode(node);
   }
 }