[turbofan]: Fix bug in register hinting

src/compiler/register-allocator.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/base/adapters.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/register-allocator.h"
 #include "src/string-stream.h"
 
 namespace v8 {
@@ skipping 178 matching lines @@
 void UsePosition::ResolveHint(UsePosition* use_pos) {
   DCHECK_NOT_NULL(use_pos);
   if (HintTypeField::decode(flags_) != UsePositionHintType::kUnresolved) return;
   hint_ = use_pos;
   flags_ = HintTypeField::update(flags_, UsePositionHintType::kUsePos);
 }
 
 
 void UsePosition::set_type(UsePositionType type, bool register_beneficial) {
   DCHECK_IMPLIES(type == UsePositionType::kRequiresSlot, !register_beneficial);
+  DCHECK_EQ(kUnassignedRegister, AssignedRegisterField::decode(flags_));
   flags_ = TypeField::encode(type) |
-           RegisterBeneficialField::encode(register_beneficial);
+           RegisterBeneficialField::encode(register_beneficial) |
+           HintTypeField::encode(HintTypeField::decode(flags_)) |
+           AssignedRegisterField::encode(kUnassignedRegister);
 }
 
 
 UseInterval* UseInterval::SplitAt(LifetimePosition pos, Zone* zone) {
   DCHECK(Contains(pos) && pos != start());
   auto after = new (zone) UseInterval(pos, end_);
   after->next_ = next_;
   next_ = nullptr;
   end_ = pos;
   return after;
@@ skipping 2845 matching lines @@
     auto eliminate = moves->PrepareInsertAfter(move);
     to_insert.push_back(move);
     if (eliminate != nullptr) to_eliminate.push_back(eliminate);
   }
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8