Generate code for some switch statements.

dart/frog/leg/ssa/optimize.dart

Index: dart/frog/leg/ssa/optimize.dart
diff --git a/dart/frog/leg/ssa/optimize.dart b/dart/frog/leg/ssa/optimize.dart
index 7fdf1b0dcabaaea1b11b0a6aa0b9d002301519ec..634111625adf00689c8f9addfb1e6172a1b03d65 100644
--- a/dart/frog/leg/ssa/optimize.dart
+++ b/dart/frog/leg/ssa/optimize.dart
@@ -326,7 +326,7 @@ class SsaDeadPhiEliminator implements OptimizationPhase {
       HPhi next = null;
       while (current != null) {
         next = current.next;
-        if (!livePhis.contains(current)) {
+        if (!livePhis.contains(current) && current.usedBy.isEmpty()) {

[ahe, 2012/03/05 22:58:35]

Not sure about this.

[Lasse Reichstein Nielsen, 2012/03/06 08:57:14]

If it isn't empty, we will hit an assert in removePhi.
If that is actually happening for you, we should make the removal smarter.
If we don't have cycles, a simple recursive removal of the usedBy elements would
work, but if we do have cycles we need to break the cycle somehow (e.g.,
removing the phi from the inputs of its usedBy elements - we know that those
must be dead phis too).

[ahe, 2012/03/06 09:16:50]

I don't understand what you're talking about. I don't have good understanding of
this part of the compiler. I can add a TODO if you tell me exactly what to write
in it.

           block.removePhi(current);
         }
         current = next;