Fix uint32-to-smi conversion in Lithium

src/hydrogen-uint32-analysis.cc

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@@ skipping 18 matching lines @@
 
 namespace v8 {
 namespace internal {
 
 
 bool HUint32AnalysisPhase::IsSafeUint32Use(HValue* val, HValue* use) {
   // Operations that operate on bits are safe.
   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);
     if (store->is_external()) {
       // Storing a value into an external integer array is a bit level
       // operation.
       if (store->value() == val) {
         // Clamping or a conversion to double should have beed inserted.
         ASSERT(store->elements_kind() != EXTERNAL_PIXEL_ELEMENTS);
         ASSERT(store->elements_kind() != EXTERNAL_FLOAT_ELEMENTS);
@@ skipping 168 matching lines @@
 
   // Some phis might have been optimistically marked with kUint32 flag.
   // Remove this flag from those phis that are unsafe and propagate
   // this information transitively potentially clearing kUint32 flag
   // from some non-phi operations that are used as operands to unsafe phis.
   UnmarkUnsafePhis();
 }
 
 
 } }  // namespace v8::internal