[turbofan] relative_id of splinters and their children.

src/compiler/register-allocator.h

 // 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.
 
 #ifndef V8_REGISTER_ALLOCATOR_H_
 #define V8_REGISTER_ALLOCATOR_H_
 
 #include "src/compiler/instruction.h"
 #include "src/ostreams.h"
 #include "src/zone-containers.h"
@@ skipping 389 matching lines @@
   void set_spilled(bool value) { bits_ = SpilledField::update(bits_, value); }
 
   UseInterval* FirstSearchIntervalForPosition(LifetimePosition position) const;
   void AdvanceLastProcessedMarker(UseInterval* to_start_of,
                                   LifetimePosition but_not_past) const;
 
   typedef BitField<bool, 0, 1> SpilledField;
   typedef BitField<int32_t, 6, 6> AssignedRegisterField;
   typedef BitField<MachineType, 12, 15> MachineTypeField;
 
+  // Unique among children and splinters of the same virtual register.
   int relative_id_;
   uint32_t bits_;
   UseInterval* last_interval_;
   UseInterval* first_interval_;
   UsePosition* first_pos_;
   TopLevelLiveRange* top_level_;
   LiveRange* next_;
   // This is used as a cache, it doesn't affect correctness.
   mutable UseInterval* current_interval_;
   // This is used as a cache, it doesn't affect correctness.
@@ skipping 108 matching lines @@
 
   TopLevelLiveRange* splintered_from() const { return splintered_from_; }
   bool IsSplinter() const { return splintered_from_ != nullptr; }
   bool MayRequireSpillRange() const {
     DCHECK(!IsSplinter());
     return !HasSpillOperand() && spill_range_ == nullptr;
   }
   void UpdateSpillRangePostMerge(TopLevelLiveRange* merged);
   int vreg() const { return vreg_; }
 
-  int GetNextChildId() { return ++last_child_id_; }
+  int GetNextChildId() {
+    return IsSplinter() ? splintered_from()->GetNextChildId()
+                        : ++last_child_id_;
+  }
+
   bool IsSpilledOnlyInDeferredBlocks() const {
     return spilled_in_deferred_blocks_;
   }
 
   struct SpillAtDefinitionList;
 
   SpillAtDefinitionList* spills_at_definition() const {
     return spills_at_definition_;
   }
   void set_last_child(LiveRange* range) { last_child_ = range; }
@@ skipping 498 matching lines @@
   RegisterAllocationData* const data_;
 
   DISALLOW_COPY_AND_ASSIGN(LiveRangeConnector);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_REGISTER_ALLOCATOR_H_