[turbofan] Introduce dedicated BitcastWordToTagged machine operator.

src/compiler/instruction-selector.cc

 // Copyright 2014 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/instruction-selector.h"
 
 #include <limits>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
@@ skipping 996 matching lines @@
     case IrOpcode::kInt64LessThanOrEqual:
       return VisitInt64LessThanOrEqual(node);
     case IrOpcode::kUint64Div:
       return MarkAsWord64(node), VisitUint64Div(node);
     case IrOpcode::kUint64LessThan:
       return VisitUint64LessThan(node);
     case IrOpcode::kUint64LessThanOrEqual:
       return VisitUint64LessThanOrEqual(node);
     case IrOpcode::kUint64Mod:
       return MarkAsWord64(node), VisitUint64Mod(node);
+    case IrOpcode::kBitcastWordToTagged:
+      return MarkAsReference(node), VisitBitcastWordToTagged(node);
     case IrOpcode::kChangeFloat32ToFloat64:
       return MarkAsFloat64(node), VisitChangeFloat32ToFloat64(node);
     case IrOpcode::kChangeInt32ToFloat64:
       return MarkAsFloat64(node), VisitChangeInt32ToFloat64(node);
     case IrOpcode::kChangeUint32ToFloat64:
       return MarkAsFloat64(node), VisitChangeUint32ToFloat64(node);
     case IrOpcode::kChangeFloat64ToInt32:
       return MarkAsWord32(node), VisitChangeFloat64ToInt32(node);
     case IrOpcode::kChangeFloat64ToUint32:
       return MarkAsWord32(node), VisitChangeFloat64ToUint32(node);
@@ skipping 219 matching lines @@
 
 void InstructionSelector::VisitStackSlot(Node* node) {
   int size = 1 << ElementSizeLog2Of(StackSlotRepresentationOf(node->op()));
   int slot = frame_->AllocateSpillSlot(size);
   OperandGenerator g(this);
 
   Emit(kArchStackSlot, g.DefineAsRegister(node),
        sequence()->AddImmediate(Constant(slot)), 0, nullptr);
 }
 
+void InstructionSelector::VisitBitcastWordToTagged(Node* node) {
+  OperandGenerator g(this);
+  Node* value = node->InputAt(0);
+  Emit(kArchNop, g.DefineSameAsFirst(node), g.Use(value));
+}
+
 // 32 bit targets do not implement the following instructions.
 #if V8_TARGET_ARCH_32_BIT
 
 void InstructionSelector::VisitWord64And(Node* node) { UNIMPLEMENTED(); }
 
 
 void InstructionSelector::VisitWord64Or(Node* node) { UNIMPLEMENTED(); }
 
 
 void InstructionSelector::VisitWord64Xor(Node* node) { UNIMPLEMENTED(); }
@@ skipping 541 matching lines @@
   return new (instruction_zone()) FrameStateDescriptor(
       instruction_zone(), state_info.type(), state_info.bailout_id(),
       state_info.state_combine(), parameters, locals, stack,
       state_info.shared_info(), outer_state);
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8