[turbofan] Move graph trimming functionality to dedicated GraphTrimmer.

src/compiler/osr.cc

Index: src/compiler/osr.cc
diff --git a/src/compiler/osr.cc b/src/compiler/osr.cc
index 4d8583bdc1bac23684f9623cd6012ca2ebcea43b..fcd04768fd7bb5720685dac59e65e951a2b82348 100644
--- a/src/compiler/osr.cc
+++ b/src/compiler/osr.cc
@@ -8,6 +8,7 @@
 #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"
@@ -337,9 +338,12 @@ void OsrHelper::Deconstruct(JSGraph* jsgraph, CommonOperatorBuilder* common,
   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());
 }
 
 
@@ -351,7 +355,6 @@ void OsrHelper::SetupFrame(Frame* frame) {
   frame->SetOsrStackSlotCount(static_cast<int>(UnoptimizedFrameSlots()));
 }
 
-
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8