Simplify generated code for trivial bailout methods.

lib/compiler/implementation/ssa/nodes.dart

 // Copyright (c) 2011, 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.
 
 interface HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
   R visitBitXor(HBitXor node);
@@ skipping 966 matching lines @@
 abstract class HCheck extends HInstruction {
   HCheck(inputs) : super(inputs);
   HInstruction get checkedInput() => inputs[0];
   bool isStatement() => true;
 }
 
 class HTypeGuard extends HCheck {
   final int state;
   final HType guardedType;
   bool isOn = false;
+  // A list of sorted variable names to be able to share a common
+  // environment between type guards with the same [state].
+  List<String> sortedVariableNames;
+
   HTypeGuard(this.guardedType, this.state, List<HInstruction> env) : super(env);
 
   void prepareGvn() {
     assert(!hasSideEffects());
     setUseGvn();
   }
 
   HInstruction get guarded() => inputs.last();
   HInstruction get checkedInput() => guarded;
 
@@ skipping 1486 matching lines @@
                         this.labels);
 
   HBasicBlock get start() {
     if (initializer !== null) return initializer.start;
     if (kind == DO_WHILE_LOOP) {
       return body.start;
     }
     return condition.start;
   }
 
+  HBasicBlock get loopHeader() {
+    return kind == DO_WHILE_LOOP ? body.start : condition.start;
+  }
+
   HBasicBlock get end() {
     if (updates !== null) return updates.end;
     if (kind == DO_WHILE_LOOP) {
       return condition.end;
     }
     return body.end;
   }
 
   static int loopType(Node node) {
     return node.accept(const LoopTypeVisitor());
@@ skipping 77 matching lines @@
   HBasicBlock get start() => expression.start;
   HBasicBlock get end() {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty());
     return statements.last().end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }