Precompilation: canonicalize lists of stackmaps.

runtime/vm/precompiler.cc

Index: runtime/vm/precompiler.cc
diff --git a/runtime/vm/precompiler.cc b/runtime/vm/precompiler.cc
index 2131fafdc551bda867454b23bafbf1b77f07f215..0425cfc812e67c9c91912d9e94032f0187702552 100644
--- a/runtime/vm/precompiler.cc
+++ b/runtime/vm/precompiler.cc
@@ -119,6 +119,7 @@ void Precompiler::DoCompileAll(
   BindStaticCalls();
 
   DedupStackmaps();
+  DedupStackmapLists();
 
   if (FLAG_trace_precompiler) {
     THR_Print("Precompiled %" Pd " functions, %" Pd " dynamic types,"
@@ -1108,6 +1109,55 @@ void Precompiler::DedupStackmaps() {
 }
 
 
+void Precompiler::DedupStackmapLists() {
+  class DedupStackmapListsVisitor : public FunctionVisitor {
+   public:
+    explicit DedupStackmapListsVisitor(Zone* zone) :
+      zone_(zone),
+      canonical_stackmap_lists_(),
+      code_(Code::Handle(zone)),
+      stackmaps_(Array::Handle(zone)),
+      stackmap_(Stackmap::Handle(zone)) {
+    }
+
+    void VisitFunction(const Function& function) {
+      if (!function.HasCode()) {
+        ASSERT(function.HasImplicitClosureFunction());
+        return;
+      }
+      code_ = function.CurrentCode();
+      stackmaps_ = code_.stackmaps();
+      if (stackmaps_.IsNull()) return;
+
+      stackmaps_ = DedupStackmapList(stackmaps_);
+      code_.set_stackmaps(stackmaps_);
+    }
+
+    RawArray* DedupStackmapList(const Array& stackmaps) {
+      const Array* canonical_stackmap_list =
+          canonical_stackmap_lists_.Lookup(&stackmaps);
+      if (canonical_stackmap_list == NULL) {
+        canonical_stackmap_lists_.Insert(
+            &Array::ZoneHandle(zone_, stackmaps.raw()));
+        return stackmaps.raw();
+      } else {
+        return canonical_stackmap_list->raw();
+      }
+    }
+
+   private:
+    Zone* zone_;
+    ArraySet canonical_stackmap_lists_;
+    Code& code_;
+    Array& stackmaps_;
+    Stackmap& stackmap_;
+  };
+
+  DedupStackmapListsVisitor visitor(Z);
+  VisitFunctions(&visitor);
+}
+
+
 void Precompiler::VisitFunctions(FunctionVisitor* visitor) {
   Library& lib = Library::Handle(Z);
   Class& cls = Class::Handle(Z);