Fix very subtle bug in HNode.changeUse.

lib/compiler/implementation/ssa/nodes.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.
 
 interface HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
   R visitBitXor(HBitXor node);
@@ skipping 913 matching lines @@
   // Change all uses of [oldInput] by [this] to [newInput]. Also
   // updates the [usedBy] of [oldInput] and [newInput].
   void changeUse(HInstruction oldInput, HInstruction newInput) {
     for (int i = 0; i < inputs.length; i++) {
       if (inputs[i] === oldInput) {
         inputs[i] = newInput;
         newInput.usedBy.add(this);
       }
     }
     List<HInstruction> oldInputUsers = oldInput.usedBy;
-    for (int i = 0; i < oldInputUsers.length; i++) {
+    int i = 0;
+    while (i < oldInputUsers.length) {
       if (oldInputUsers[i] == this) {
         oldInputUsers[i] = oldInputUsers[oldInput.usedBy.length - 1];
-        oldInputUsers.length = oldInputUsers.length - 1;
+        oldInputUsers.length--;
+      } else {
+        i++;
       }
     }
   }
 
   // Compute the set of users of this instruction that is dominated by
   // [other].
   Set<HInstruction> dominatedUsers(HInstruction other) {
     // Keep track of all instructions that we have to deal with later
     // and count the number of them that are in the current block.
     Set<HInstruction> users = new Set<HInstruction>();
     int usersInCurrentBlock = 0;
 
     // Run through all the users and see if they are dominated or
     // potentially dominated by [other].
-    HBasicBlock block = other.block;
+    HBasicBlock otherBlock = other.block;
     for (int i = 0, length = usedBy.length; i < length; i++) {
       HInstruction current = usedBy[i];
-      if (current !== other && block.dominates(current.block)) {
-        if (current.block === block) usersInCurrentBlock++;
+      if (current !== other && otherBlock.dominates(current.block)) {
+        if (current.block === otherBlock) usersInCurrentBlock++;
         users.add(current);
       }
     }
 
     // Run through all the instructions before [other] and remove them
     // from the users set.
     if (usersInCurrentBlock > 0) {
-      HInstruction current = block.first;
+      HInstruction current = otherBlock.first;
       while (current !== other) {
         if (users.contains(current)) {
           users.remove(current);
           if (--usersInCurrentBlock == 0) break;
         }
         current = current.next;
       }
     }
 
     return users;
@@ skipping 1684 matching lines @@
   HBasicBlock get start() => expression.start;
   HBasicBlock get end() {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty());
     return statements.last().end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }