[turbofan] Introduce DeoptimizeIf And DeoptimizeUnless common operators.

src/compiler/branch-elimination.cc

 // Copyright 2015 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/branch-elimination.h"
 
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/simplified-operator.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 BranchElimination::BranchElimination(Editor* editor, JSGraph* js_graph,
                                      Zone* zone)
     : AdvancedReducer(editor),
+      jsgraph_(js_graph),
       node_conditions_(zone, js_graph->graph()->NodeCount()),
       zone_(zone),
       dead_(js_graph->graph()->NewNode(js_graph->common()->Dead())) {}
 
-
 BranchElimination::~BranchElimination() {}
 
 
 Reduction BranchElimination::Reduce(Node* node) {
   switch (node->opcode()) {
     case IrOpcode::kDead:
       return NoChange();
+    case IrOpcode::kDeoptimizeIf:
+    case IrOpcode::kDeoptimizeUnless:
+      return ReduceDeoptimizeConditional(node);
     case IrOpcode::kMerge:
       return ReduceMerge(node);
     case IrOpcode::kLoop:
       return ReduceLoop(node);
     case IrOpcode::kBranch:
       return ReduceBranch(node);
     case IrOpcode::kIfFalse:
       return ReduceIf(node, false);
     case IrOpcode::kIfTrue:
       return ReduceIf(node, true);
@@ skipping 29 matching lines @@
           default:
             UNREACHABLE();
         }
       }
       return Replace(dead());
     }
   }
   return TakeConditionsFromFirstControl(node);
 }
 
+Reduction BranchElimination::ReduceDeoptimizeConditional(Node* node) {
+  DCHECK(node->opcode() == IrOpcode::kDeoptimizeIf ||
+         node->opcode() == IrOpcode::kDeoptimizeUnless);
+  bool condition_is_true = node->opcode() == IrOpcode::kDeoptimizeUnless;
+  Node* condition = NodeProperties::GetValueInput(node, 0);
+  Node* frame_state = NodeProperties::GetValueInput(node, 1);
+  Node* effect = NodeProperties::GetEffectInput(node);
+  Node* control = NodeProperties::GetControlInput(node);
+  ControlPathConditions const* conditions = node_conditions_.Get(control);
+  // If we do not know anything about the predecessor, do not propagate just
+  // yet because we will have to recompute anyway once we compute the
+  // predecessor.
+  if (conditions == nullptr) {
+    DCHECK_NULL(node_conditions_.Get(node));
+    return NoChange();
+  }
+  Maybe<bool> condition_value = conditions->LookupCondition(condition);
+  if (condition_value.IsJust()) {
+    // If we know the condition we can discard the branch.
+    if (condition_is_true == condition_value.FromJust()) {
+      return Replace(control);

[Jarin, 2016/02/24 08:56:38]

Perhaps add a comment saying that we do not need to update the conditions here
because we are replacing with the 'control' node and that node already contains
the right information.

[Benedikt Meurer, 2016/02/24 09:04:56]

Done.

+    } else {
+      control = graph()->NewNode(common()->Deoptimize(DeoptimizeKind::kEager),
+                                 frame_state, effect, control);
+      // TODO(bmeurer): This should be on the AdvancedReducer somehow.
+      NodeProperties::MergeControlToEnd(graph(), common(), control);
+      Revisit(graph()->end());
+      return Replace(dead());
+    }
+  }
+  return UpdateConditions(
+      node, conditions->AddCondition(zone_, condition, condition_is_true));
+}
 
 Reduction BranchElimination::ReduceIf(Node* node, bool is_true_branch) {
   // Add the condition to the list arriving from the input branch.
   Node* branch = NodeProperties::GetControlInput(node, 0);
   const ControlPathConditions* from_branch = node_conditions_.Get(branch);
   // If we do not know anything about the predecessor, do not propagate just
   // yet because we will have to recompute anyway once we compute the
   // predecessor.
   if (from_branch == nullptr) {
     DCHECK(node_conditions_.Get(node) == nullptr);
@@ skipping 168 matching lines @@
         this_condition->is_true != other_condition->is_true) {
       return false;
     }
     this_condition = this_condition->next;
     other_condition = other_condition->next;
   }
   UNREACHABLE();
   return false;
 }
 
+Graph* BranchElimination::graph() const { return jsgraph()->graph(); }
+
+CommonOperatorBuilder* BranchElimination::common() const {
+  return jsgraph()->common();
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8