[turbofan] LiveRange splitting at interval boundary fix.

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 339 matching lines @@
 
   UseInterval* after = nullptr;
   while (current != nullptr) {
     if (current->Contains(position)) {
       after = current->SplitAt(position, zone);
       break;
     }
     auto next = current->next();
     if (next->start() >= position) {
       split_at_start = (next->start() == position);
+      after = next;
+      current->set_next(nullptr);
       break;
     }
     current = next;
   }
 
   // Partition original use intervals to the two live ranges.
   auto before = current;
-  if (after == nullptr) after = before->next();
   result->last_interval_ =
       (last_interval_ == before)
           ? after            // Only interval in the range after split.
           : last_interval_;  // Last interval of the original range.
   result->first_interval_ = after;
   last_interval_ = before;
 
   // Find the last use position before the split and the first use
   // position after it.
   auto use_after = first_pos_;
@@ skipping 2463 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