[turbofan] Introduce a dedicated ConvertTaggedHoleToUndefined operator.

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 696 matching lines @@
       break;
     case IrOpcode::kStringCharCodeAt:
       state = LowerStringCharCodeAt(node, *effect, *control);
       break;
     case IrOpcode::kCheckFloat64Hole:
       state = LowerCheckFloat64Hole(node, frame_state, *effect, *control);
       break;
     case IrOpcode::kCheckTaggedHole:
       state = LowerCheckTaggedHole(node, frame_state, *effect, *control);
       break;
+    case IrOpcode::kConvertTaggedHoleToUndefined:
+      state = LowerConvertTaggedHoleToUndefined(node, *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;
     case IrOpcode::kEnsureWritableFastElements:
@@ skipping 1684 matching lines @@
   control = effect =
       graph()->NewNode(common()->DeoptimizeIf(DeoptimizeReason::kHole), check,
                        frame_state, effect, control);
 
   return ValueEffectControl(value, effect, control);
 }
 
 EffectControlLinearizer::ValueEffectControl
 EffectControlLinearizer::LowerCheckTaggedHole(Node* node, Node* frame_state,
                                               Node* effect, Node* control) {
-  CheckTaggedHoleMode mode = CheckTaggedHoleModeOf(node->op());
   Node* value = node->InputAt(0);
   Node* check = graph()->NewNode(machine()->WordEqual(), value,
                                  jsgraph()->TheHoleConstant());
-  switch (mode) {
-    case CheckTaggedHoleMode::kConvertHoleToUndefined:
-      value = graph()->NewNode(
-          common()->Select(MachineRepresentation::kTagged, BranchHint::kFalse),
-          check, jsgraph()->UndefinedConstant(), value);
-      break;
-    case CheckTaggedHoleMode::kNeverReturnHole:
-      control = effect =
-          graph()->NewNode(common()->DeoptimizeIf(DeoptimizeReason::kHole),
-                           check, frame_state, effect, control);
-      break;
-  }
+  control = effect =
+      graph()->NewNode(common()->DeoptimizeIf(DeoptimizeReason::kHole), check,
+                       frame_state, effect, control);
 
   return ValueEffectControl(value, effect, control);
 }
+
+EffectControlLinearizer::ValueEffectControl
+EffectControlLinearizer::LowerConvertTaggedHoleToUndefined(Node* node,
+                                                           Node* effect,
+                                                           Node* control) {
+  Node* value = node->InputAt(0);
+  Node* check = graph()->NewNode(machine()->WordEqual(), value,
+                                 jsgraph()->TheHoleConstant());
+  Node* branch =
+      graph()->NewNode(common()->Branch(BranchHint::kFalse), check, control);
+
+  Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+  Node* vtrue = jsgraph()->UndefinedConstant();
+
+  Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+  Node* vfalse = value;
+
+  control = graph()->NewNode(common()->Merge(2), if_true, if_false);
+  value = graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
+                           vtrue, vfalse, control);
+
+  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);
@@ skipping 839 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