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..1aa1891731ed58e196e7071e3c61d8f38c8fb694 100644
--- a/dart/frog/leg/ssa/optimize.dart
+++ b/dart/frog/leg/ssa/optimize.dart
@@ -326,7 +326,9 @@ class SsaDeadPhiEliminator implements OptimizationPhase {
       HPhi next = null;
       while (current != null) {
         next = current.next;
-        if (!livePhis.contains(current)) {
+        if (!livePhis.contains(current)
+            // TODO(ahe): Not sure the following is correct.

[ngeoffray, 2012/03/06 11:49:48]

Why did you need to add this? Was it on one test case or all?

[ahe, 2012/03/06 12:24:35]

Just one test case, I think.

[ngeoffray, 2012/03/06 12:32:55]

Worth fixing? I'd rather keep the bug and try to fix it the right way.

[ahe, 2012/03/06 13:10:51]

I wanted to get rid of the assertion error. This is one of the problematic
assertions I ranted about a few days ago. However, I could not figure out how to
turn it into an internal error.

I think a compiler crash is extremely bad, and I will do whatever it takes to
get rid of them.

As far as I understand, this change is semantically correct, but may generate
suboptimal code.

[ngeoffray, 2012/03/07 08:55:31]

But you're fixing a symptom, not the bug. I think we both agree that we
definitely prefer *failing* (not crashing) tests compared to adding symptom
fixes. To avoid the crash, why don't you do:

if (!current.usedBy.isEmpty()) compiler.internalError("blah", instruction: phi);

If this does not work, you could also file a bug and reference it here.

+            && current.usedBy.isEmpty()) {
           block.removePhi(current);
         }
         current = next;