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)
@@ -1136,7 +1136,7 @@
                              HInstruction input,
                              HType convertedType) {
     HTypeConversion newInput;
-    Set<HInstruction> dominatedUsers = input.dominatedUsers(dominator.first);
+    Set<HInstruction> dominatedUsers = input.dominatedUsers(null, dominator);
     for (HInstruction user in dominatedUsers) {

[kasperl, 2012/08/20 11:37:22]

How about returning if dominatedUsers.isEmpty and then just creating newInput
right away (outside the loop)? Seems cleaner than checking if newInput is null
inside the loop.

       if (newInput === null) {
         newInput = new HTypeConversion(convertedType, input);