Fix issue 9939 by making the body of a try block have two successors: the join block after the try/…

sdk/lib/_internal/compiler/implementation/ssa/builder.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.
 
 part of ssa;
 
 /**
  * A special element for the extra parameter taken by intercepted
  * methods. We need to override [Element.computeType] because our
  * optimizers may look at its declared type.
@@ skipping 4599 matching lines @@
     HBasicBlock startTryBlock;
     HBasicBlock endTryBlock;
     HBasicBlock startCatchBlock;
     HBasicBlock endCatchBlock;
     HBasicBlock startFinallyBlock;
     HBasicBlock endFinallyBlock;
 
     startTryBlock = graph.addNewBlock();
     open(startTryBlock);
     visit(node.tryBlock);
-    if (!isAborted()) endTryBlock = close(new HGoto());
+    // We use a [HExitTry] instead of a [HGoto] for the try block
+    // because it will have multiple successors: the join block, and
+    // the catch or finally block.
+    if (!isAborted()) endTryBlock = close(new HExitTry());
     SubGraph bodyGraph = new SubGraph(startTryBlock, lastOpenedBlock);
     SubGraph catchGraph = null;
     HLocalValue exception = null;
 
     if (!node.catchBlocks.isEmpty) {
       localsHandler = new LocalsHandler.from(savedLocals);
       startCatchBlock = graph.addNewBlock();
       open(startCatchBlock);
       // TODO(kasperl): Bad smell. We shouldn't be constructing elements here.
       // Note that the name of this element is irrelevant.
@@ skipping 138 matching lines @@
     enterBlock.addSuccessor(startTryBlock);
     addOptionalSuccessor(enterBlock, startCatchBlock);
     addOptionalSuccessor(enterBlock, startFinallyBlock);
     enterBlock.addSuccessor(exitBlock);
 
     // The body has either the catch or the finally block as successor.
     if (endTryBlock != null) {
       assert(startCatchBlock != null || startFinallyBlock != null);
       endTryBlock.addSuccessor(
           startCatchBlock != null ? startCatchBlock : startFinallyBlock);
+      endTryBlock.addSuccessor(exitBlock);
     }
 
     // The catch block has either the finally or the exit block as
     // successor.
     if (endCatchBlock != null) {
       endCatchBlock.addSuccessor(
           startFinallyBlock != null ? startFinallyBlock : exitBlock);
     }
 
     // The finally block has the exit block as successor.
@@ skipping 442 matching lines @@
           new HSubGraphBlockInformation(elseBranch.graph));
 
     HBasicBlock conditionStartBlock = conditionBranch.block;
     conditionStartBlock.setBlockFlow(info, joinBlock);
     SubGraph conditionGraph = conditionBranch.graph;
     HIf branch = conditionGraph.end.last;
     assert(branch is HIf);
     branch.blockInformation = conditionStartBlock.blockFlow;
   }
 }