Revert of [turbofan] Remove redundant code.

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 2425 matching lines @@
     auto current = unhandled_live_ranges().back();
     unhandled_live_ranges().pop_back();
     DCHECK(UnhandledIsSorted());
     auto position = current->Start();
 #ifdef DEBUG
     allocation_finger_ = position;
 #endif
     TRACE("Processing interval %d:%d start=%d\n", current->TopLevel()->vreg(),
           current->relative_id(), position.value());
 
+    if (current->IsTopLevel() && !current->TopLevel()->HasNoSpillType()) {
+      TRACE("Live range %d:%d already has a spill operand\n",
+            current->TopLevel()->vreg(), current->relative_id());
+      auto next_pos = position;
+      if (next_pos.IsGapPosition()) {
+        next_pos = next_pos.NextStart();
+      }
+      auto pos = current->NextUsePositionRegisterIsBeneficial(next_pos);
+      // If the range already has a spill operand and it doesn't need a
+      // register immediately, split it and spill the first part of the range.
+      if (pos == nullptr) {
+        Spill(current);
+        continue;
+      } else if (pos->pos() > current->Start().NextStart()) {
+        // Do not spill live range eagerly if use position that can benefit from
+        // the register is too close to the start of live range.
+        SpillBetween(current, current->Start(), pos->pos());
+        DCHECK(UnhandledIsSorted());
+        continue;
+      }
+    }
+
     if (current->IsTopLevel() && TryReuseSpillForPhi(current->TopLevel()))
       continue;
 
     for (size_t i = 0; i < active_live_ranges().size(); ++i) {
       auto cur_active = active_live_ranges()[i];
       if (cur_active->End() <= position) {
         ActiveToHandled(cur_active);
         --i;  // The live range was removed from the list of active live ranges.
       } else if (!cur_active->Covers(position)) {
         ActiveToInactive(cur_active);
@@ skipping 965 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