[turbofan] Polymorphic inlining - try merge map check dispatch with function call dispatch.

This improves delta blue by about >5%. Unfortunately, this still does not help load
and check elimination because we do not learn maps from control flow.

Change-Id: I49a97dbc40576b9bc80c87ec2b459e37ba9b4440
Bug: v8:5267
Reviewed-on: https://chromium-review.googlesource.com/618328
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47405}

src/compiler/js-inlining-heuristic.cc

@@ -220,6 +220,275 @@ void JSInliningHeuristic::Finalize() {
   }
 }
 
+namespace {
+
+struct NodeAndIndex {
+  Node* node;
+  int index;
+};
+
+bool CollectStateValuesOwnedUses(Node* node, Node* state_values,
+                                 NodeAndIndex* uses_buffer, size_t* use_count,
+                                 size_t max_uses) {
+  // Only accumulate states that are not shared with other users.
+  if (state_values->UseCount() > 1) return true;
+  for (int i = 0; i < state_values->InputCount(); i++) {
+    Node* input = state_values->InputAt(i);
+    if (input->opcode() == IrOpcode::kStateValues) {
+      if (!CollectStateValuesOwnedUses(node, input, uses_buffer, use_count,
+                                       max_uses)) {
+        return false;
+      }
+    } else if (input == node) {
+      if (*use_count >= max_uses) return false;
+      uses_buffer[*use_count] = {state_values, i};
+      (*use_count)++;
+    }
+  }
+  return true;
+}
+
+}  // namespace
+
+Node* JSInliningHeuristic::DuplicateStateValuesAndRename(Node* state_values,
+                                                         Node* from, Node* to,
+                                                         StateCloneMode mode) {
+  // Only rename in states that are not shared with other users. This needs to
+  // be in sync with the condition in {CollectStateValuesOwnedUses}.
+  if (state_values->UseCount() > 1) return state_values;
+  Node* copy = mode == kChangeInPlace ? state_values : nullptr;
+  for (int i = 0; i < state_values->InputCount(); i++) {
+    Node* input = state_values->InputAt(i);
+    Node* processed;
+    if (input->opcode() == IrOpcode::kStateValues) {
+      processed = DuplicateStateValuesAndRename(input, from, to, mode);
+    } else if (input == from) {
+      processed = from;
+    } else {
+      processed = input;
+    }
+    if (processed != input) {
+      if (!copy) {
+        copy = graph()->CloneNode(state_values);
+      }
+      copy->ReplaceInput(i, processed);
+    }
+  }
+  return copy ? copy : state_values;
+}
+
+namespace {
+
+bool CollectFrameStateUniqueUses(Node* node, Node* frame_state,
+                                 NodeAndIndex* uses_buffer, size_t* use_count,
+                                 size_t max_uses) {
+  // Only accumulate states that are not shared with other users.
+  if (frame_state->UseCount() > 1) return true;
+  if (frame_state->InputAt(kFrameStateStackInput) == node) {
+    if (*use_count >= max_uses) return false;
+    uses_buffer[*use_count] = {frame_state, kFrameStateStackInput};
+    (*use_count)++;
+  }
+  if (!CollectStateValuesOwnedUses(node,
+                                   frame_state->InputAt(kFrameStateLocalsInput),
+                                   uses_buffer, use_count, max_uses)) {
+    return false;
+  }
+  return true;
+}
+
+}  // namespace
+
+Node* JSInliningHeuristic::DuplicateFrameStateAndRename(Node* frame_state,
+                                                        Node* from, Node* to,
+                                                        StateCloneMode mode) {
+  // Only rename in states that are not shared with other users. This needs to
+  // be in sync with the condition in {DuplicateFrameStateAndRename}.
+  if (frame_state->UseCount() > 1) return frame_state;
+  Node* copy = mode == kChangeInPlace ? frame_state : nullptr;
+  if (frame_state->InputAt(kFrameStateStackInput) == from) {
+    if (!copy) {
+      copy = graph()->CloneNode(frame_state);
+    }
+    copy->ReplaceInput(kFrameStateStackInput, to);
+  }
+  Node* locals = frame_state->InputAt(kFrameStateLocalsInput);
+  Node* new_locals = DuplicateStateValuesAndRename(locals, from, to, mode);
+  if (new_locals != locals) {
+    if (!copy) {
+      copy = graph()->CloneNode(frame_state);
+    }
+    copy->ReplaceInput(kFrameStateLocalsInput, new_locals);
+  }
+  return copy ? copy : frame_state;
+}
+
+bool JSInliningHeuristic::TryReuseDispatch(Node* node, Node* callee,
+                                           Candidate const& candidate,
+                                           Node** if_successes, Node** calls,
+                                           Node** inputs, int input_count) {
+  // We will try to reuse the control flow branch created for computing
+  // the {callee} target of the call. We only reuse the branch if there
+  // is no side-effect between the call and the branch, and if the callee is
+  // only used as the target (and possibly also in the related frame states).
+
+  int const num_calls = candidate.num_functions;
+
+  DCHECK_EQ(IrOpcode::kPhi, callee->opcode());
+  DCHECK_EQ(num_calls, callee->op()->ValueInputCount());
+
+  // If there is a control node between the callee computation
+  // and the call, bail out.
+  Node* merge = NodeProperties::GetControlInput(callee);
+  if (NodeProperties::GetControlInput(node) != merge) return false;
+
+  // If there is a non-checkpoint effect node between the callee computation
+  // and the call, bail out. We will drop any checkpoint between the call and
+  // the callee phi because the callee computation should have its own
+  // checkpoint that the call can fall back to.
+  Node* checkpoint = nullptr;
+  Node* effect = NodeProperties::GetEffectInput(node);
+  if (effect->opcode() == IrOpcode::kCheckpoint) {
+    checkpoint = effect;
+    if (NodeProperties::GetControlInput(checkpoint) != merge) return false;
+    effect = NodeProperties::GetEffectInput(effect);
+  }
+  if (effect->opcode() != IrOpcode::kEffectPhi) return false;
+  if (NodeProperties::GetControlInput(effect) != merge) return false;
+  Node* effect_phi = effect;
+
+  // We must replace the callee phi with the appropriate constant in
+  // the entire subgraph reachable by inputs from the call (terminating
+  // at phis and merges). Since we do not want to walk (and later duplicate)
+  // the subgraph here, we limit the possible uses to this set:
+  //
+  // 1. In the call (as a target).
+  // 2. The checkpoint between the call and the callee computation merge.
+  // 3. The lazy deoptimization frame state.
+  //
+  // This corresponds to the most common pattern, where the function is
+  // called with only local variables or constants as arguments.
+  //
+  // To check the uses, we first collect all the occurrences of callee in 1, 2
+  // and 3, and then we check that all uses of callee are in the collected
+  // occurrences. If there is an unaccounted use, we do not try to rewire
+  // the control flow.
+  //
+  // Note: With CFG, this would be much easier and more robust - we would just
+  // duplicate all the nodes between the merge and the call, replacing all
+  // occurrences of the {callee} phi with the appropriate constant.
+
+  // First compute the set of uses that are only reachable from 2 and 3.
+  const size_t kMaxUses = 8;
+  NodeAndIndex replaceable_uses[kMaxUses];
+  size_t replaceable_uses_count = 0;
+
+  // Collect the uses to check case 2.
+  if (checkpoint) {
+    if (!CollectFrameStateUniqueUses(callee, checkpoint->InputAt(0),
+                                     replaceable_uses, &replaceable_uses_count,
+                                     kMaxUses)) {
+      return false;
+    }
+  }
+
+  // Collect the uses to check case 3.
+  Node* frame_state = NodeProperties::GetFrameStateInput(node);
+  if (!CollectFrameStateUniqueUses(callee, frame_state, replaceable_uses,
+                                   &replaceable_uses_count, kMaxUses)) {
+    return false;
+  }
+
+  // Bail out if there is a use of {callee} that is not reachable from 1, 2
+  // and 3.
+  for (Edge edge : callee->use_edges()) {
+    // Case 1 (use by the call as a target).
+    if (edge.from() == node && edge.index() == 0) continue;
+    // Case 2 and 3 - used in checkpoint and/or lazy deopt frame states.
+    bool found = false;
+    for (size_t i = 0; i < replaceable_uses_count; i++) {
+      if (replaceable_uses[i].node == edge.from() &&
+          replaceable_uses[i].index == edge.index()) {
+        found = true;
+        break;
+      }
+    }
+    if (!found) return false;
+  }
+
+  // Clone the call and the framestate, including the uniquely reachable
+  // state values, making sure that we replace the phi with the constant.
+  for (int i = 0; i < num_calls; ++i) {
+    // Clone the calls for each branch.
+    // We need to specialize the calls to the correct target, effect, and
+    // control. We also need to duplicate the frame state, and change all
+    // the uses of the callee to the constant callee.
+    Node* target = callee->InputAt(i);
+    Node* effect = effect_phi->InputAt(i);
+    Node* control = merge->InputAt(i);
+    Node* new_frame_state = DuplicateFrameStateAndRename(
+        frame_state, callee, target,
+        (i == num_calls - 1) ? kChangeInPlace : kCloneState);
+
+    inputs[0] = target;
+    inputs[input_count - 3] = new_frame_state;
+    inputs[input_count - 2] = effect;
+    inputs[input_count - 1] = control;
+    calls[i] = if_successes[i] =
+        graph()->NewNode(node->op(), input_count, inputs);
+  }
+
+  // Mark the control inputs dead, so that we can kill the merge.
+  node->ReplaceInput(input_count - 1, jsgraph()->Dead());
+  callee->ReplaceInput(num_calls, jsgraph()->Dead());
+  effect_phi->ReplaceInput(num_calls, jsgraph()->Dead());
+  if (checkpoint) {
+    checkpoint->ReplaceInput(2, jsgraph()->Dead());
+  }
+
+  merge->Kill();
+  return true;
+}
+
+void JSInliningHeuristic::CreateOrReuseDispatch(Node* node, Node* callee,
+                                                Candidate const& candidate,
+                                                Node** if_successes,
+                                                Node** calls, Node** inputs,
+                                                int input_count) {
+  if (TryReuseDispatch(node, callee, candidate, if_successes, calls, inputs,
+                       input_count)) {
+    return;
+  }
+
+  Node* fallthrough_control = NodeProperties::GetControlInput(node);
+  int const num_calls = candidate.num_functions;
+
+  // Create the appropriate control flow to dispatch to the cloned calls.
+  for (int i = 0; i < num_calls; ++i) {
+    // TODO(2206): Make comparison be based on underlying SharedFunctionInfo
+    // instead of the target JSFunction reference directly.
+    Node* target = jsgraph()->HeapConstant(candidate.functions[i]);
+    if (i != (num_calls - 1)) {
+      Node* check =
+          graph()->NewNode(simplified()->ReferenceEqual(), callee, target);
+      Node* branch =
+          graph()->NewNode(common()->Branch(), check, fallthrough_control);
+      fallthrough_control = graph()->NewNode(common()->IfFalse(), branch);
+      if_successes[i] = graph()->NewNode(common()->IfTrue(), branch);
+    } else {
+      if_successes[i] = fallthrough_control;
+    }
+
+    // Clone the calls for each branch.
+    // The first input to the call is the actual target (which we specialize
+    // to the known {target}); the last input is the control dependency.
+    inputs[0] = target;
+    inputs[input_count - 1] = if_successes[i];
+    calls[i] = if_successes[i] =
+        graph()->NewNode(node->op(), input_count, inputs);
+  }
+}
+
 Reduction JSInliningHeuristic::InlineCandidate(Candidate const& candidate,
                                                bool force_inline) {
   int const num_calls = candidate.num_functions;
@@ -242,7 +511,6 @@ Reduction JSInliningHeuristic::InlineCandidate(Candidate const& candidate,
   Node* calls[kMaxCallPolymorphism + 1];
   Node* if_successes[kMaxCallPolymorphism];
   Node* callee = NodeProperties::GetValueInput(node, 0);
-  Node* fallthrough_control = NodeProperties::GetControlInput(node);
 
   // Setup the inputs for the cloned call nodes.
   int const input_count = node->InputCount();
@@ -252,28 +520,8 @@ Reduction JSInliningHeuristic::InlineCandidate(Candidate const& candidate,
   }
 
   // Create the appropriate control flow to dispatch to the cloned calls.
-  for (int i = 0; i < num_calls; ++i) {
-    // TODO(2206): Make comparison be based on underlying SharedFunctionInfo
-    // instead of the target JSFunction reference directly.
-    Node* target = jsgraph()->HeapConstant(candidate.functions[i]);
-    if (i != (num_calls - 1)) {
-      Node* check =
-          graph()->NewNode(simplified()->ReferenceEqual(), callee, target);
-      Node* branch =
-          graph()->NewNode(common()->Branch(), check, fallthrough_control);
-      fallthrough_control = graph()->NewNode(common()->IfFalse(), branch);
-      if_successes[i] = graph()->NewNode(common()->IfTrue(), branch);
-    } else {
-      if_successes[i] = fallthrough_control;
-    }
-
-    // The first input to the call is the actual target (which we specialize
-    // to the known {target}); the last input is the control dependency.
-    inputs[0] = target;
-    inputs[input_count - 1] = if_successes[i];
-    calls[i] = if_successes[i] =
-        graph()->NewNode(node->op(), input_count, inputs);
-  }
+  CreateOrReuseDispatch(node, callee, candidate, if_successes, calls, inputs,
+                        input_count);
 
   // Check if we have an exception projection for the call {node}.
   Node* if_exception = nullptr;

src/compiler/js-inlining-heuristic.h

@@ -64,6 +64,17 @@ class JSInliningHeuristic final : public AdvancedReducer {
   // Dumps candidates to console.
   void PrintCandidates();
   Reduction InlineCandidate(Candidate const& candidate, bool force_inline);
+  void CreateOrReuseDispatch(Node* node, Node* callee,
+                             Candidate const& candidate, Node** if_successes,
+                             Node** calls, Node** inputs, int input_count);
+  bool TryReuseDispatch(Node* node, Node* callee, Candidate const& candidate,
+                        Node** if_successes, Node** calls, Node** inputs,
+                        int input_count);
+  enum StateCloneMode { kCloneState, kChangeInPlace };
+  Node* DuplicateFrameStateAndRename(Node* frame_state, Node* from, Node* to,
+                                     StateCloneMode mode);
+  Node* DuplicateStateValuesAndRename(Node* state_values, Node* from, Node* to,
+                                      StateCloneMode mode);
 
   CommonOperatorBuilder* common() const;
   Graph* graph() const;