Initial support for polymorphic inlining.

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
diff --git a/runtime/vm/flow_graph_builder.cc b/runtime/vm/flow_graph_builder.cc
index b4b833ad9bd9c7a97ad7bfd6a73fe396d64403c2..ec4247a162ceddd48a43282d5ec23ab8dfdaf2af 100644
--- a/runtime/vm/flow_graph_builder.cc
+++ b/runtime/vm/flow_graph_builder.cc
@@ -96,6 +96,15 @@ void InlineExitCollector::AddExit(ReturnInstr* exit) {
 }
 
 
+void InlineExitCollector::Union(const InlineExitCollector* other) {
+  // It doesn't make sense to combine different calls or calls from
+  // different graphs.
+  ASSERT(caller_graph_ == other->caller_graph_);
+  ASSERT(call_ == other->call_);
+  exits_.AddArray(other->exits_);
+}
+
+
 int InlineExitCollector::LowestBlockIdFirst(const Data* a, const Data* b) {
   return (a->exit_block->block_id() - b->exit_block->block_id());
 }
@@ -132,7 +141,7 @@ Definition* InlineExitCollector::JoinReturns(BlockEntryInstr** exit_block,
     caller_graph_->set_max_block_id(join_id);
     JoinEntryInstr* join =
         new JoinEntryInstr(join_id, CatchClauseNode::kInvalidTryIndex);
-    join->InheritDeoptTarget(call_);
+    join->InheritDeoptTargetAfter(call_);
 
     // The dominator set of the join is the intersection of the dominator
     // sets of all the predecessors.  If we keep the dominator sets ordered
@@ -179,7 +188,8 @@ Definition* InlineExitCollector::JoinReturns(BlockEntryInstr** exit_block,
             // We either exhausted the dominators for this block before
             // exhausting the current intersection, or else we found a block
             // on the path from the root of the tree that is not in common.
-            ASSERT(j >= 2);
+            // I.e., there cannot be an empty set of dominators.
+            ASSERT(j > 0);
             join_dominators.TruncateTo(j);
             break;
           }