Fix a bug in the placement of minus-zero checks and in GVN....

src/hydrogen.cc

Index: src/hydrogen.cc
===================================================================
--- src/hydrogen.cc	(revision 6529)
+++ src/hydrogen.cc	(working copy)
@@ -1813,15 +1813,6 @@
                                               HValue* use,
                                               Representation to,
                                               bool is_truncating) {
-  // Propagate flags for negative zero checks upwards from conversions
-  // int32-to-tagged and int32-to-double.
-  Representation from = value->representation();
-  if (from.IsInteger32()) {
-    ASSERT(to.IsTagged() || to.IsDouble());
-    BitVector visited(GetMaximumValueID());
-    PropagateMinusZeroChecks(value, &visited);
-  }
-
   // Insert the representation change right before its use. For phi-uses we
   // insert at the end of the corresponding predecessor.
   HBasicBlock* insert_block = use->block();
@@ -1984,6 +1975,28 @@
 }
 
 
+void HGraph::ComputeMinusZeroChecks() {
+  for (int i = 0; i < blocks_.length(); ++i) {
+    for (HInstruction* current = blocks_[i]->first();
+         current != NULL;
+         current = current->next()) {
+      if (current->IsChange()) {
+        HChange* change = HChange::cast(current);
+        // Propagate flags for negative zero checks upwards from conversions
+        // int32-to-tagged and int32-to-double.
+        Representation from = change->value()->representation();
+        ASSERT(from.Equals(change->from()));
+        if (from.IsInteger32()) {
+          ASSERT(change->to().IsTagged() || change->to().IsDouble());
+          BitVector visited(GetMaximumValueID());

[William Hesse, 2011/01/31 12:22:54]

Is this allocation a problem?  Can you reuse one?

[fschneider, 2011/01/31 12:34:44]

Good point. Done.

+          PropagateMinusZeroChecks(change->value(), &visited);
+        }
+      }
+    }
+  }
+}
+
+
 // Implementation of utility classes to represent an expression's context in
 // the AST.
 AstContext::AstContext(HGraphBuilder* owner, Expression::Context kind)
@@ -2243,6 +2256,7 @@
   graph_->InitializeInferredTypes();
   graph_->Canonicalize();
   graph_->InsertRepresentationChanges();
+  graph_->ComputeMinusZeroChecks();
 
   // Eliminate redundant stack checks on backwards branches.
   HStackCheckEliminator sce(graph_);