Fix uint32-to-smi conversion in Lithium

src/hydrogen-uint32-analysis.cc

Index: src/hydrogen-uint32-analysis.cc
diff --git a/src/hydrogen-uint32-analysis.cc b/src/hydrogen-uint32-analysis.cc
index 835a198d4d8b53f42d06542806f3381116ea1869..fbd6b354ea44c24665b7f6484b6be297b4ff856d 100644
--- a/src/hydrogen-uint32-analysis.cc
+++ b/src/hydrogen-uint32-analysis.cc
@@ -36,7 +36,14 @@ bool HUint32AnalysisPhase::IsSafeUint32Use(HValue* val, HValue* use) {
   if (use->IsBitwise() || use->IsShl() || use->IsSar() || use->IsShr()) {
     return true;
   } else if (use->IsChange() || use->IsSimulate()) {
-    // Conversions and deoptimization have special support for unt32.
+    // Conversions and deoptimization have special support for uint32.
+    // This ASSERT guards that the conversion in question is actually
+    // implemented. Do not extend the whitelist without adding
+    // support to LChunkBuilder::DoChange().
+    ASSERT(!use->IsChange() ||

[Vyacheslav Egorov (Google), 2013/10/31 10:05:36]

I would make it 

else if (use->IsSimulate()) {
  // Deoptimization has special support.
  return true;
} else if (use->IsChange()) {
  // Conversion has special support. This assert (the rest of the comment)...
  ASSERT(...);
}

to not have somewhat confusing !use->IsChange()

+           HChange::cast(use)->to().IsDouble() ||
+           HChange::cast(use)->to().IsSmi() ||
+           HChange::cast(use)->to().IsTagged());
     return true;
   } else if (use->IsStoreKeyed()) {
     HStoreKeyed* store = HStoreKeyed::cast(use);