Use 'default:' for the first bailout-case with more than one target.

lib/compiler/implementation/ssa/codegen.dart

 // Copyright (c) 2012, 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.
 
 class SsaCodeGeneratorTask extends CompilerTask {
   final JavaScriptBackend backend;
   SsaCodeGeneratorTask(JavaScriptBackend backend)
       : this.backend = backend,
         super(backend.compiler);
   String get name() => 'SSA code generator';
@@ skipping 2848 matching lines @@
   void endLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
   }
 }
 
 class SsaUnoptimizedCodeGenerator extends SsaCodeGenerator {
 
   final CodeBuffer setup;
   final CodeBuffer newParameters;
   final List<String> labels;
   int labelId = 0;
+  /**
+   * Keeps track if a bailout switch already used its [:default::] clause. New
+   * bailout-switches just push [:false:] on the stack and replace it when
+   * they used the [:default::] clause.
+   */
+  final List<bool> defaultClauseUsedInBailoutStack;
 
   SsaBailoutPropagator propagator;
   HInstruction savedFirstInstruction;
 
   SsaUnoptimizedCodeGenerator(backend, work, parameters, parameterNames)
     : super(backend, work, parameters, parameterNames),
       setup = new CodeBuffer(),
       newParameters = new CodeBuffer(),
-      labels = <String>[];
+      labels = <String>[],
+      defaultClauseUsedInBailoutStack = <bool>[];
 
   String pushLabel() {
     String label = 'L${labelId++}';
     labels.addLast(label);
     return label;
   }
 
   String popLabel() {
     return labels.removeLast();
   }
@@ skipping 105 matching lines @@
       }
       setup.add('$name = env$i;\n');
       i++;
     }
     setup.add('      break;\n');
   }
 
   void startBailoutCase(List<HTypeGuard> bailouts1,
                         List<HTypeGuard> bailouts2) {
     indent--;
-    handleBailoutCase(bailouts1);
-    handleBailoutCase(bailouts2);
+    if (!defaultClauseUsedInBailoutStack.last() &&
+        bailouts1.length + bailouts2.length >= 2) {
+      addIndented('default:\n');
+      int len = defaultClauseUsedInBailoutStack.length;
+      defaultClauseUsedInBailoutStack[len - 1] = true;
+    } else {
+      handleBailoutCase(bailouts1);
+      handleBailoutCase(bailouts2);
+    }
     indent++;
   }
 
   void handleBailoutCase(List<HTypeGuard> guards) {
-    for (int i = 0, len = guards.length; i < len; i++) {
-      addIndented('case ${guards[i].state}:\n');
+    if (!defaultClauseUsedInBailoutStack.last() && guards.length >= 2) {
+      addIndented('default:\n');
+      int len = defaultClauseUsedInBailoutStack.length;
+      defaultClauseUsedInBailoutStack[len - 1] = true;
+    } else {
+      for (int i = 0, len = guards.length; i < len; i++) {
+        addIndented('case ${guards[i].state}:\n');
+      }
     }
   }
 
   void startBailoutSwitch() {
+    defaultClauseUsedInBailoutStack.add(false);
     addIndented('switch (state) {\n');
     indent++;
     addIndented('case 0:\n');
     indent++;
   }
 
   void endBailoutSwitch() {
     indent--; // Close 'case'.
     indent--;
     addIndented('}\n');  // Close 'switch'.
+    defaultClauseUsedInBailoutStack.removeLast();
   }
 
   void beginLoop(HBasicBlock block) {
     String newLabel = pushLabel();
     if (block.hasGuards()) {
       startBailoutCase(block.guards, const <HTypeGuard>[]);
     }
 
     addIndentation();
     HLoopInformation loopInformation = block.loopInformation;
@@ skipping 107 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }