[turbofan] Merge group spill ranges.

src/compiler/greedy-allocator.h

 // 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.
 
 #ifndef V8_GREEDY_ALLOCATOR_H_
 #define V8_GREEDY_ALLOCATOR_H_
 
 #include "src/compiler/coalesced-live-ranges.h"
 #include "src/compiler/register-allocator.h"
 #include "src/zone-containers.h"
@@ skipping 161 matching lines @@
 
   // Finds the first call instruction in the path of this range. Splits before
   // and requeues that segment (if any), spills the section over the call, and
   // returns the section after the call. The return is:
   // - same range, if no call was found
   // - nullptr, if the range finished at the call and there's no "after the
   //   call" portion.
   // - the portion after the call.
   LiveRange* GetRemainderAfterSplittingAroundFirstCall(LiveRange* range);
 
+  // While we attempt to merge spill ranges later on in the allocation pipeline,
+  // we want to ensure group elements get merged. Waiting until later may hinder
+  // merge-ability, since the pipeline merger (being naive) may create conflicts
+  // between spill ranges of group members.
+  void TryReuseSpillRangesForGroups();
+
   // Necessary heuristic: spill when all else failed.
   void SpillRangeAsLastResort(LiveRange* range);
 
   void AssignRangeToRegister(int reg_id, LiveRange* range);
 
   Zone* local_zone_;
   ZoneVector<CoalescedLiveRanges*> allocations_;
   AllocationScheduler scheduler_;
   ZoneVector<LiveRangeGroup*> groups_;
 
   DISALLOW_COPY_AND_ASSIGN(GreedyAllocator);
 };
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_GREEDY_ALLOCATOR_H_