[turbofan] First rudimentary inlining heuristic.

This is a first prototype for a rudimentary inlining heuristic allowing
enabling of general inlining based existing budget flags. Also note that
this approach does not yet work for multi-level inlining, for now the
list of candidates is processed exactly once.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1406543002

Cr-Commit-Position: refs/heads/master@{#31249}

src/compiler/js-inlining-heuristic.cc

@@ -4,6 +4,7 @@
 
 #include "src/compiler/js-inlining-heuristic.h"
 
+#include "src/compiler/dead-code-elimination.h"  // TODO(mstarzinger): Remove!
 #include "src/compiler/node-matchers.h"
 #include "src/objects-inl.h"
 
@@ -24,9 +25,88 @@ Reduction JSInliningHeuristic::Reduce(Node* node) {
     return inliner_.ReduceJSCallFunction(node, function);
   }
 
-  // All other functions are only handled with general inlining.
-  if (mode_ == kRestrictedInlining) return NoChange();
-  return inliner_.ReduceJSCallFunction(node, function);
+  // Handling of special inlining modes right away:
+  //  - For restricted inlining: stop all handling at this point.
+  //  - For stressing inlining: immediately handle all functions.
+  switch (mode_) {
+    case kRestrictedInlining:
+      return NoChange();
+    case kStressInlining:
+      return inliner_.ReduceJSCallFunction(node, function);
+    case kGeneralInlining:
+      break;
+  }
+
+  // ---------------------------------------------------------------------------
+  // Everything below this line is part of the inlining heuristic.
+  // ---------------------------------------------------------------------------
+
+  // Built-in functions are handled by the JSBuiltinReducer.
+  if (function->shared()->HasBuiltinFunctionId()) return NoChange();
+
+  // Quick check on source code length to avoid parsing large candidate.
+  if (function->shared()->SourceSize() > FLAG_max_inlined_source_size) {
+    return NoChange();
+  }
+
+  // Quick check on the size of the AST to avoid parsing large candidate.
+  if (function->shared()->ast_node_count() > FLAG_max_inlined_nodes) {
+    return NoChange();
+  }
+
+  // Gather feedback on how often this call site has been hit before.
+  CallFunctionParameters p = CallFunctionParametersOf(node->op());
+  CallICNexus nexus(p.feedback().vector(), p.feedback().slot());
+  int calls = nexus.ExtractCallCount();
+
+  // ---------------------------------------------------------------------------
+  // Everything above this line is part of the inlining heuristic.
+  // ---------------------------------------------------------------------------
+
+  // In the general case we remember the candidate for later.
+  candidates_.push_back({function, node, calls});
+  return NoChange();
+}
+
+
+void JSInliningHeuristic::ProcessCandidates() {
+  if (candidates_.empty()) return;  // Nothing to do without candidates.
+  std::sort(candidates_.begin(), candidates_.end(), Compare);
+  if (FLAG_trace_turbo_inlining) PrintCandidates();
+
+  int cumulative_count = 0;
+  for (const Candidate& candidate : candidates_) {
+    if (cumulative_count > FLAG_max_inlined_nodes_cumulative) break;
+    inliner_.ReduceJSCallFunction(candidate.node, candidate.function);
+    cumulative_count += candidate.function->shared()->ast_node_count();
+  }
+
+  // TODO(mstarzinger): Temporary workaround to eliminate dead control from the
+  // graph being introduced by the inliner. Make this part of the pipeline.
+  GraphReducer graph_reducer(local_zone_, jsgraph_->graph(), jsgraph_->Dead());
+  DeadCodeElimination dead_code_elimination(&graph_reducer, jsgraph_->graph(),
+                                            jsgraph_->common());
+  graph_reducer.AddReducer(&dead_code_elimination);
+  graph_reducer.ReduceGraph();
+}
+
+
+// static
+bool JSInliningHeuristic::Compare(const Candidate& left,
+                                  const Candidate& right) {
+  return left.calls > right.calls;
+}
+
+
+void JSInliningHeuristic::PrintCandidates() {
+  PrintF("Candidates for inlining (size=%zu):\n", candidates_.size());
+  for (const Candidate& candidate : candidates_) {
+    PrintF("  id:%d, calls:%d, size[source]:%d, size[ast]:%d / %s\n",
+           candidate.node->id(), candidate.calls,
+           candidate.function->shared()->SourceSize(),
+           candidate.function->shared()->ast_node_count(),
+           candidate.function->shared()->DebugName()->ToCString().get());
+  }
 }
 
 }  // namespace compiler

src/compiler/js-inlining-heuristic.h

@@ -13,18 +13,37 @@ namespace compiler {
 
 class JSInliningHeuristic final : public AdvancedReducer {
  public:
-  enum Mode { kRestrictedInlining, kGeneralInlining };
+  enum Mode { kGeneralInlining, kRestrictedInlining, kStressInlining };
   JSInliningHeuristic(Editor* editor, Mode mode, Zone* local_zone,
                       CompilationInfo* info, JSGraph* jsgraph)
       : AdvancedReducer(editor),
         mode_(mode),
-        inliner_(editor, local_zone, info, jsgraph) {}
+        local_zone_(local_zone),
+        jsgraph_(jsgraph),
+        inliner_(editor, local_zone, info, jsgraph),
+        candidates_(local_zone) {}
 
   Reduction Reduce(Node* node) final;
 
+  // Processes the list of candidates gathered while the reducer was running,
+  // and inlines call sites that the heuristic determines to be important.
+  void ProcessCandidates();
+
  private:
+  struct Candidate {
+    Handle<JSFunction> function;  // The call target being inlined.
+    Node* node;                   // The call site at which to inline.
+    int calls;                    // Number of times the call site was hit.
+  };
+
+  static bool Compare(const Candidate& left, const Candidate& right);
+  void PrintCandidates();
+
   Mode const mode_;
+  Zone* local_zone_;
+  JSGraph* jsgraph_;
   JSInliner inliner_;
+  ZoneVector<Candidate> candidates_;
 };
 
 }  // namespace compiler

src/compiler/pipeline.cc

@@ -542,6 +542,7 @@ struct InliningPhase {
     AddReducer(data, &graph_reducer, &context_specialization);
     AddReducer(data, &graph_reducer, &inlining);
     graph_reducer.ReduceGraph();
+    inlining.ProcessCandidates();
   }
 };