Compensate for the lack of code motion in licm.

sdk/lib/_internal/compiler/implementation/ssa/optimize.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;
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
@@ skipping 1022 matching lines @@
     }
   }
 
   void moveLoopInvariantCodeFromBlock(HBasicBlock block,
                                       HBasicBlock loopHeader,
                                       int changesFlags) {
     assert(block.parentLoopHeader == loopHeader || block == loopHeader);
     HBasicBlock preheader = loopHeader.predecessors[0];
     int dependsFlags = SideEffects.computeDependsOnFlags(changesFlags);
     HInstruction instruction = block.first;
-    bool firstInstructionInLoop = block == loopHeader;
+    bool isLoopAlwaysTaken() {
+      HInstruction instruction = loopHeader.last;
+      return instruction is HGoto || instruction.inputs[0].isConstantTrue();
+    }
+    bool firstInstructionInLoop = block == loopHeader
+        // Compensate for lack of code motion.
+        || (blockChangesFlags[loopHeader.id] == 0
+            && isLoopAlwaysTaken()
+            && loopHeader.successors[0] == block);
     while (instruction != null) {
       HInstruction next = instruction.next;
       if (instruction.useGvn()
           && (!instruction.canThrow() || firstInstructionInLoop)
           && !instruction.sideEffects.dependsOn(dependsFlags)) {
         bool loopInvariantInputs = true;
         List<HInstruction> inputs = instruction.inputs;
         for (int i = 0, length = inputs.length; i < length; i++) {
           if (isInputDefinedAfterDominator(inputs[i], preheader)) {
             loopInvariantInputs = false;
@@ skipping 285 matching lines @@
       // that knows it is not of a specific Type.
     }
 
     for (HIf ifUser in notIfUsers) {
       changeUsesDominatedBy(ifUser.elseBlock, input, convertedType);
       // TODO(ngeoffray): Also change uses for the then block on a HType
       // that knows it is not of a specific Type.
     }
   }
 }