Implement 'as' operator.

lib/compiler/implementation/ssa/variable_allocator.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.
 
 /**
  * The [LiveRange] class covers a range where an instruction is live.
  */
 class LiveRange {
   final int start;
   // [end] is not final because it can be updated due to loops.
@@ skipping 266 matching lines @@
     // Update all instructions that are liveIns in [header] to have a
     // range that covers the loop.
     env.liveInstructions.forEach((HInstruction instruction, int id) {
       LiveInterval range = env.liveIntervals.putIfAbsent(
           instruction, () => new LiveInterval());
       range.loopUpdate(env.startId, lastId);
       env.liveInstructions[instruction] = lastId;
     });
 
     env.removeLoopMarker(header);
-   
-    // Update all liveIns set to contain the liveIns of [header]. 
+
+    // Update all liveIns set to contain the liveIns of [header].
     liveInstructions.forEach((HBasicBlock block, LiveEnvironment other) {
       if (other.loopMarkers.containsKey(header)) {
         env.liveInstructions.forEach((HInstruction instruction, int id) {
           other.liveInstructions[instruction] = id;
         });
         other.removeLoopMarker(header);
         env.loopMarkers.forEach((k, v) { other.loopMarkers[k] = v; });
       }
     });
   }
@@ skipping 250 matching lines @@
     if (generateAtUseSite.contains(instruction)) return false;
     // A [HCheck] instruction that has control flow needs a name only if its
     // checked input needs a name (e.g. a check [HConstant] does not
     // need a name).
     if (instruction is HCheck && instruction.isControlFlow()) {
       HCheck check = instruction;
       return needsName(instruction.checkedInput);
     }
     return true;
   }
- 
+
   /**
    * Returns whether [instruction] dies at the instruction [at].
    */
   bool diesAt(HInstruction instruction, HInstruction at) {
     LiveInterval atInterval = liveIntervals[at];
     LiveInterval instructionInterval = liveIntervals[instruction];
     int start = atInterval.start;
     return instructionInterval.diesAt(start);
   }
 
@@ skipping 21 matching lines @@
       if (!needsName(input)) {
         names.addAssignment(predecessor, input, phi);
       } else {
         names.addCopy(predecessor, input, phi);
       }
     }
 
     namer.allocateName(phi);
   }
 }