Avoid critical edge on do/while, and do not make handleLoopInfo return conditionnaly false: block b…

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;
 
 class Interceptors {
   Compiler compiler;
   Interceptors(Compiler this.compiler);
 
@@ skipping 2031 matching lines @@
         bodyEntryBlock.setBlockFlow(info, conditionBlock);
       }
       open(conditionBlock);
 
       visit(node.condition);
       assert(!isAborted());
       HInstruction conditionInstruction = popBoolified();
       conditionEndBlock = close(
           new HLoopBranch(conditionInstruction, HLoopBranch.DO_WHILE_LOOP));
 
-      conditionEndBlock.addSuccessor(loopEntryBlock);  // The back-edge.
+      HBasicBlock avoidEdge = addNewBlock();

[floitsch, 2012/11/16 14:05:43]

avoidCriticalEdge, or but comment somewhere.

[ngeoffray, 2012/11/16 14:14:59]

Renamed to avoidCriticalEdge.

+      conditionEndBlock.addSuccessor(avoidEdge);  // The back-edge.
+      open(avoidEdge);
+      close(new HGoto());
+      avoidEdge.addSuccessor(loopEntryBlock);
+
       conditionExpression =
           new SubExpression(conditionBlock, conditionEndBlock);
     }
 
     loopEntryBlock.postProcessLoopHeader();
 
     endLoop(loopEntryBlock, conditionEndBlock, jumpHandler, localsHandler);
     jumpHandler.close();
 
     SubGraph bodyGraph = new SubGraph(bodyEntryBlock, bodyExitBlock);
@@ skipping 2778 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;
   }
 }