Initial support for polymorphic inlining.

runtime/vm/flow_graph.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph.h"
 
 #include "vm/bit_vector.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/intermediate_language.h"
 #include "vm/longjump.h"
@@ skipping 829 matching lines @@
     }
   }
 
   for (BlockIterator it(postorder_iterator()); !it.Done(); it.Advance()) {
     JoinEntryInstr* join = it.Current()->AsJoinEntry();
     if (join != NULL) join->RemoveDeadPhis(constant_null());
   }
 }
 
 
+void FlowGraph::RemoveRedefinitions() {

[Florian Schneider, 2013/05/03 10:41:36]

This is very similar to what we do with ConstraintInstr after array bounds check
elimination. Could you share the code?

[Kevin Millikin (Google), 2013/05/03 11:47:38]

That one uses a maintained list of constraints, this one searches in the graph
for redefinitions.  I don't really want to maintain a list of redefinitions in
the graph as part of this change, so I'll leave it as is.

However, it does point out a bug in this code: it does not properly handle
redefinitions of redefinitions and nothing prevents them from arising.

+  // Remove redefinition instructions inserted to inhibit hoisting.
+  for (BlockIterator block_it = reverse_postorder_iterator();
+       !block_it.Done();
+       block_it.Advance()) {
+    for (ForwardInstructionIterator instr_it(block_it.Current());
+         !instr_it.Done();
+         instr_it.Advance()) {
+      RedefinitionInstr* redefinition = instr_it.Current()->AsRedefinition();
+      if (redefinition != NULL) {
+        redefinition->ReplaceUsesWith(redefinition->value()->definition());
+        instr_it.RemoveCurrentFromGraph();
+      }
+    }
+  }
+}
+
+
 // Find the natural loop for the back edge m->n and attach loop information
 // to block n (loop header). The algorithm is described in "Advanced Compiler
 // Design & Implementation" (Muchnick) p192.
 static void FindLoop(BlockEntryInstr* m,
                      BlockEntryInstr* n,
                      intptr_t num_blocks) {
   GrowableArray<BlockEntryInstr*> stack;
   BitVector* loop = new BitVector(num_blocks);
 
   loop->Add(n->preorder_number());
@@ skipping 171 matching lines @@
 }
 
 
 bool BlockEffects::IsSideEffectFreePath(BlockEntryInstr* from,
                                         BlockEntryInstr* to) const {
   return available_at_[to->postorder_number()]->Contains(
       from->postorder_number());
 }
 
 }  // namespace dart