[turbofan] Run checkpoint elimination early.

This runs the existing checkpoint elimination during the "inlining"
optimization phase. It will eliminate redundant checkpoint nodes and
hence reduce graph size earlier. After this change the reducer in
question runs during {InliningPhase} as well as {TypedLoweringPhase}.

R=bmeurer@chromium.org

Review-Url: https://codereview.chromium.org/2670763003
Cr-Commit-Position: refs/heads/master@{#42918}

src/compiler/pipeline.cc

@@ -777,6 +777,7 @@ struct InliningPhase {
     JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
     DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
                                               data->common());
+    CheckpointElimination checkpoint_elimination(&graph_reducer);
     CommonOperatorReducer common_reducer(&graph_reducer, data->graph(),
                                          data->common(), data->machine());
     JSCallReducer::Flags call_reducer_flags = JSCallReducer::kNoFlags;
@@ -818,6 +819,7 @@ struct InliningPhase {
             ? JSIntrinsicLowering::kDeoptimizationEnabled
             : JSIntrinsicLowering::kDeoptimizationDisabled);
     AddReducer(data, &graph_reducer, &dead_code_elimination);
+    AddReducer(data, &graph_reducer, &checkpoint_elimination);
     AddReducer(data, &graph_reducer, &common_reducer);
     if (data->info()->is_frame_specializing()) {
       AddReducer(data, &graph_reducer, &frame_specialization);