[turbofan] Introduce CheckHole and CheckHoleNaN operators.

src/compiler/effect-control-linearizer.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/effect-control-linearizer.h"
 
 #include "src/code-factory.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/linkage.h"
@@ skipping 437 matching lines @@
       break;
     case IrOpcode::kObjectIsUndetectable:
       state = LowerObjectIsUndetectable(node, *effect, *control);
       break;
     case IrOpcode::kStringFromCharCode:
       state = LowerStringFromCharCode(node, *effect, *control);
       break;
     case IrOpcode::kCheckIf:
       state = LowerCheckIf(node, frame_state, *effect, *control);
       break;
+    case IrOpcode::kCheckHole:
+      state = LowerCheckHole(node, frame_state, *effect, *control);
+      break;
+    case IrOpcode::kCheckHoleNaN:
+      state = LowerCheckHoleNaN(node, frame_state, *effect, *control);
+      break;
     case IrOpcode::kPlainPrimitiveToNumber:
       state = LowerPlainPrimitiveToNumber(node, *effect, *control);
       break;
     case IrOpcode::kPlainPrimitiveToWord32:
       state = LowerPlainPrimitiveToWord32(node, *effect, *control);
       break;
     case IrOpcode::kPlainPrimitiveToFloat64:
       state = LowerPlainPrimitiveToFloat64(node, *effect, *control);
       break;
     default:
@@ skipping 821 matching lines @@
 EffectControlLinearizer::LowerCheckIf(Node* node, Node* frame_state,
                                       Node* effect, Node* control) {
   NodeProperties::ReplaceEffectInput(node, effect);
   NodeProperties::ReplaceControlInput(node, control);
   node->InsertInput(graph()->zone(), 1, frame_state);
   NodeProperties::ChangeOp(node, common()->DeoptimizeIf());
   return ValueEffectControl(node, node, node);
 }
 
 EffectControlLinearizer::ValueEffectControl
+EffectControlLinearizer::LowerCheckHole(Node* node, Node* frame_state,
+                                        Node* effect, Node* control) {
+  CheckHoleMode mode = CheckHoleModeOf(node->op());
+  Node* value = node->InputAt(0);
+  Node* check = graph()->NewNode(machine()->WordEqual(), value,
+                                 jsgraph()->TheHoleConstant());
+  switch (mode) {
+    case CheckHoleMode::kAllowReturnHole:

[Jarin, 2016/06/15 11:18:43]

This is confusing - it does not return hole, it turns hole into undefined. Could
we have a name that somehow implies that (Like kConvertHoleToUndefined or some
such)?

[Benedikt Meurer, 2016/06/15 11:39:09]

Done.

+      value = graph()->NewNode(
+          common()->Select(MachineRepresentation::kTagged, BranchHint::kFalse),
+          check, jsgraph()->UndefinedConstant(), value);
+      break;
+    case CheckHoleMode::kNeverReturnHole:
+      control = effect = graph()->NewNode(common()->DeoptimizeIf(), check,

[Jarin, 2016/06/15 11:18:43]

kDeoptimizeIfHole?

[Benedikt Meurer, 2016/06/15 11:39:09]

I kinda prefer the never-return-hole thing here.

+                                          frame_state, effect, control);
+      break;
+  }
+
+  // Make sure the lowered node does not appear in any use lists.
+  node->TrimInputCount(0);
+
+  return ValueEffectControl(value, effect, control);
+}
+
+EffectControlLinearizer::ValueEffectControl
+EffectControlLinearizer::LowerCheckHoleNaN(Node* node, Node* frame_state,
+                                           Node* effect, Node* control) {
+  // If we reach this point w/o eliminating the {node} that's marked
+  // with allow-return-hole, we cannot do anything, so just deoptimize
+  // in case of the hole NaN (similar to Crankshaft).
+  Node* value = node->InputAt(0);
+  Node* check = graph()->NewNode(
+      machine()->Word32Equal(),
+      graph()->NewNode(machine()->Float64ExtractHighWord32(), value),
+      jsgraph()->Int32Constant(kHoleNanUpper32));
+  control = effect = graph()->NewNode(common()->DeoptimizeIf(), check,
+                                      frame_state, effect, control);
+
+  // Make sure the lowered node does not appear in any use lists.
+  node->TrimInputCount(0);
+
+  return ValueEffectControl(value, effect, control);
+}
+
+EffectControlLinearizer::ValueEffectControl
 EffectControlLinearizer::AllocateHeapNumberWithValue(Node* value, Node* effect,
                                                      Node* control) {
   Node* result = effect = graph()->NewNode(
       simplified()->Allocate(NOT_TENURED),
       jsgraph()->Int32Constant(HeapNumber::kSize), effect, control);
   effect = graph()->NewNode(simplified()->StoreField(AccessBuilder::ForMap()),
                             result, jsgraph()->HeapNumberMapConstant(), effect,
                             control);
   effect = graph()->NewNode(
       simplified()->StoreField(AccessBuilder::ForHeapNumberValue()), result,
@@ skipping 184 matching lines @@
         isolate(), graph()->zone(), callable.descriptor(), 0, flags,
         Operator::kNoThrow);
     to_number_operator_.set(common()->Call(desc));
   }
   return to_number_operator_.get();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8