[turbofan] round robin register picking

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/zone-containers.h"
 
@@ skipping 553 matching lines @@
   ZoneVector<LiveRange*> fixed_live_ranges_;
   ZoneVector<LiveRange*> fixed_double_live_ranges_;
   ZoneList<LiveRange*> unhandled_live_ranges_;
   ZoneList<LiveRange*> active_live_ranges_;
   ZoneList<LiveRange*> inactive_live_ranges_;
   ZoneList<LiveRange*> reusable_slots_;
   ZoneList<SpillRange*> spill_ranges_;
 
   RegisterKind mode_;
   int num_registers_;
+  uint8_t first_register_to_try_;  // For robin round register picking.
 
   BitVector* assigned_registers_;
   BitVector* assigned_double_registers_;
 
   // Indicates success or failure during register allocation.
   bool allocation_ok_;
 
 #ifdef DEBUG
   LifetimePosition allocation_finger_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(RegisterAllocator);
 };
 
 }
 }
 }  // namespace v8::internal::compiler
 
 #endif  // V8_REGISTER_ALLOCATOR_H_