[turbofan] escape analysis supports arguments object and rest elements

src/compiler/escape-analysis-reducer.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/escape-analysis-reducer.h"
 
 #include "src/compiler/all-nodes.h"
 #include "src/compiler/js-graph.h"
+#include "src/compiler/simplified-operator.h"
+#include "src/compiler/type-cache.h"
 #include "src/counters.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 #ifdef DEBUG
 #define TRACE(...)                                    \
   do {                                                \
     if (FLAG_trace_turbo_escape) PrintF(__VA_ARGS__); \
@@ skipping 60 matching lines @@
             break;
           default:
             break;
         }
       }
       if (!depends_on_object_state) {
         fully_reduced_.Add(node->id());
       }
       return NoChange();
     }
+    case IrOpcode::kNewUnmappedArgumentsElements:
+      arguments_elements_.insert(node);
+    // Fallthrough.

[Jarin, 2017/02/27 13:24:34]

Could we get rid of the fallthrough?

Case fallthroughs are evil.

     default:
       // TODO(sigurds): Change this to GetFrameStateInputCount once
       // it is working. For now we use EffectInputCount > 0 to determine
       // whether a node might have a frame state input.
       if (exists_virtual_allocate_ && node->op()->EffectInputCount() > 0) {
         return ReduceFrameStateUses(node);
       }
       break;
   }
   return NoChange();
@@ skipping 291 matching lines @@
 #ifdef DEBUG
   AllNodes all(zone(), jsgraph()->graph());
   for (Node* node : all.reachable) {
     if (node->opcode() == IrOpcode::kAllocate) {
       CHECK(!escape_analysis_->IsVirtual(node));
     }
   }
 #endif  // DEBUG
 }
 
+void EscapeAnalysisReducer::Finalize() {
+  for (Node* node : arguments_elements_) {
+    DCHECK(node->opcode() == IrOpcode::kNewUnmappedArgumentsElements);
+
+    Node* arguments_frame = NodeProperties::GetValueInput(node, 0);
+    if (arguments_frame->opcode() != IrOpcode::kArgumentsFrame) continue;
+    Node* arguments_length = NodeProperties::GetValueInput(node, 1);
+    if (arguments_length->opcode() != IrOpcode::kArgumentsLength) continue;
+
+    bool escaping_use = false;
+    ZoneVector<Node*> loads(zone());
+    for (Edge edge : node->use_edges()) {
+      Node* use = edge.from();
+      if (!NodeProperties::IsValueEdge(edge)) continue;
+      switch (use->opcode()) {
+        case IrOpcode::kStateValues:
+        case IrOpcode::kTypedStateValues:
+        case IrOpcode::kObjectState:
+        case IrOpcode::kTypedObjectState:
+          break;
+        case IrOpcode::kLoadElement:
+          loads.push_back(use);
+          break;
+        case IrOpcode::kLoadField:
+          if (FieldAccessOf(use->op()).offset == FixedArray::kLengthOffset) {
+            loads.push_back(use);
+            break;
+          }
+        // Fallthrough.

[Jarin, 2017/02/27 13:24:34]

Could not you say here 
if (...) {
  load.push_back(use);
} else {
  escaping_use = true;
}
break;

+        default:
+          if (!use->use_edges().empty()) {

[Jarin, 2017/02/27 13:24:34]

Explain in a comment what this check does, please.

+            escaping_use = true;
+            break;
+          }
+      }
+      if (escaping_use) break;
+    }
+    if (!escaping_use) {
+      int formal_parameter_count =
+          FormalParameterCountOf(arguments_length->op());
+      Node* arguments_elements_state = jsgraph()->graph()->NewNode(
+          jsgraph()->common()->ArgumentsElementsState(
+              IsRestLengthOf(arguments_length->op())));
+      NodeProperties::SetType(arguments_elements_state, Type::OtherInternal());
+      ReplaceWithValue(node, arguments_elements_state);
+
+      ElementAccess stack_access;
+      stack_access.base_is_tagged = BaseTaggedness::kUntaggedBase;
+      // Reduce base address by {kPointerSize} such that (length - index)
+      // resolves to the right position.
+      stack_access.header_size =
+          CommonFrameConstants::kFixedFrameSizeAboveFp - kPointerSize;
+      stack_access.type = Type::NonInternal();
+      stack_access.machine_type = MachineType::AnyTagged();
+      stack_access.write_barrier_kind = WriteBarrierKind::kNoWriteBarrier;
+      const Operator* load_stack_op =
+          jsgraph()->simplified()->LoadElement(stack_access);
+
+      for (Node* load : loads) {
+        switch (load->opcode()) {
+          case IrOpcode::kLoadElement: {
+            Node* index = NodeProperties::GetValueInput(load, 1);
+            // {offset} is a reverted index starting from 1. The base address is
+            // adapted to allow offsets starting from 1.
+            Node* offset = jsgraph()->graph()->NewNode(
+                jsgraph()->simplified()->NumberSubtract(), arguments_length,
+                index);
+            NodeProperties::SetType(offset,
+                                    TypeCache::Get().kArgumentsLengthType);
+            NodeProperties::ReplaceValueInput(load, arguments_frame, 0);
+            NodeProperties::ReplaceValueInput(load, offset, 1);
+            NodeProperties::ChangeOp(load, load_stack_op);
+            break;
+          }
+          case IrOpcode::kLoadField: {
+            DCHECK_EQ(FieldAccessOf(load->op()).offset,
+                      FixedArray::kLengthOffset);
+            Node* length = NodeProperties::GetValueInput(node, 1);
+            ReplaceWithValue(load, length);
+            break;
+          }
+          default:
+            UNREACHABLE();
+        }
+      }
+    }
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8