[turbofan] Move graph trimming functionality to dedicated GraphTrimmer.

src/compiler/osr.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler.h"
 #include "src/compiler/all-nodes.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/control-reducer.h"
 #include "src/compiler/frame.h"
 #include "src/compiler/graph.h"
+#include "src/compiler/graph-trimmer.h"
 #include "src/compiler/graph-visualizer.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/loop-analysis.h"
 #include "src/compiler/node.h"
 #include "src/compiler/node-marker.h"
 #include "src/compiler/osr.h"
 #include "src/scopes.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 309 matching lines @@
   osr_loop_entry->ReplaceUses(graph->start());
   osr_loop_entry->Kill();
 
   // Normally the control reducer removes loops whose first input is dead,
   // but we need to avoid that because the osr_loop is reachable through
   // the second input, so reduce it and its phis manually.
   osr_loop->ReplaceInput(0, dead);
   Node* node = ControlReducer::ReduceMerge(jsgraph, osr_loop);
   if (node != osr_loop) osr_loop->ReplaceUses(node);
 
-  // Run the normal control reduction, which naturally trims away the dead
-  // parts of the graph.
+  // Run control reduction and graph trimming.
   ControlReducer::ReduceGraph(tmp_zone, jsgraph);
+  GraphTrimmer trimmer(tmp_zone, jsgraph->graph());
+  NodeVector roots(tmp_zone);
+  jsgraph->GetCachedNodes(&roots);
+  trimmer.TrimGraph(roots.begin(), roots.end());
 }
 
 
 void OsrHelper::SetupFrame(Frame* frame) {
   // The optimized frame will subsume the unoptimized frame. Do so by reserving
   // the first spill slots.
   frame->ReserveSpillSlots(UnoptimizedFrameSlots());
   // The frame needs to be adjusted by the number of unoptimized frame slots.
   frame->SetOsrStackSlotCount(static_cast<int>(UnoptimizedFrameSlots()));
 }
 
-
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8