Add an optional parameter to the dominatedUsers function in case we want to analyze the whole block,

lib/compiler/implementation/ssa/optimize.dart

Index: lib/compiler/implementation/ssa/optimize.dart
===================================================================
--- lib/compiler/implementation/ssa/optimize.dart	(revision 10938)
+++ lib/compiler/implementation/ssa/optimize.dart	(working copy)
@@ -682,7 +682,7 @@
   HIntegerCheck insertIntegerCheck(HInstruction node, HInstruction value) {
     HIntegerCheck check = new HIntegerCheck(value);
     node.block.addBefore(node, check);
-    Set<HInstruction> dominatedUsers = value.dominatedUsers(check);
+    Set<HInstruction> dominatedUsers = value.dominatedUsers(node);
     for (HInstruction user in dominatedUsers) {
       user.changeUse(value, check);
     }
@@ -1135,13 +1135,12 @@
   void changeUsesDominatedBy(HBasicBlock dominator,
                              HInstruction input,
                              HType convertedType) {
-    HTypeConversion newInput;
     Set<HInstruction> dominatedUsers = input.dominatedUsers(dominator.first);
+    if (dominatedUsers.isEmpty()) return;
+
+    HTypeConversion newInput = new HTypeConversion(convertedType, input);
+    dominator.addBefore(dominator.first, newInput);
     for (HInstruction user in dominatedUsers) {

[kasperl, 2012/08/20 12:58:35]

Use dominatedUsers.forEach?

[ngeoffray, 2012/08/20 13:01:32]

Sure. Personal preference?

-      if (newInput === null) {
-        newInput = new HTypeConversion(convertedType, input);
-        dominator.addBefore(dominator.first, newInput);
-      }
       user.changeUse(input, newInput);
     }
   }