[turbofan] put late ssa deconstruction in register allocator behind a flag

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 180 matching lines @@
   LiveRange* next() const { return next_; }
   bool IsChild() const { return parent() != NULL; }
   int id() const { return id_; }
   bool IsFixed() const { return id_ < 0; }
   bool IsEmpty() const { return first_interval() == NULL; }
   InstructionOperand* CreateAssignedOperand(Zone* zone) const;
   int assigned_register() const { return assigned_register_; }
   int spill_start_index() const { return spill_start_index_; }
   void set_assigned_register(int reg, Zone* zone);
   void MakeSpilled(Zone* zone);
+  bool is_phi() const { return is_phi_; }
+  void set_is_phi(bool is_phi) { is_phi_ = is_phi; }
+  bool is_non_loop_phi() const { return is_non_loop_phi_; }
+  void set_is_non_loop_phi(bool is_non_loop_phi) {
+    is_non_loop_phi_ = is_non_loop_phi;
+  }
 
   // Returns use position in this live range that follows both start
   // and last processed use position.
   // Modifies internal state of live range!
   UsePosition* NextUsePosition(LifetimePosition start);
 
   // Returns use position for which register is required in this live
   // range and which follows both start and last processed use position
   // Modifies internal state of live range!
   UsePosition* NextRegisterPosition(LifetimePosition start);
@@ skipping 77 matching lines @@
 
  private:
   void ConvertOperands(Zone* zone);
   void ConvertUsesToOperand(InstructionOperand* op);
   UseInterval* FirstSearchIntervalForPosition(LifetimePosition position) const;
   void AdvanceLastProcessedMarker(UseInterval* to_start_of,
                                   LifetimePosition but_not_past) const;
 
   int id_;
   bool spilled_;
+  bool is_phi_;
+  bool is_non_loop_phi_;
   RegisterKind kind_;
   int assigned_register_;
   UseInterval* last_interval_;
   UseInterval* first_interval_;
   UsePosition* first_pos_;
   LiveRange* parent_;
   LiveRange* next_;
   // This is used as a cache, it doesn't affect correctness.
   mutable UseInterval* current_interval_;
   UsePosition* last_processed_use_;
@@ skipping 48 matching lines @@
   const ZoneVector<LiveRange*>& fixed_double_live_ranges() const {
     return fixed_double_live_ranges_;
   }
   InstructionSequence* code() const { return code_; }
   // This zone is for datastructures only needed during register allocation.
   Zone* local_zone() const { return local_zone_; }
 
   // Phase 1 : insert moves to account for fixed register operands.
   void MeetRegisterConstraints();
 
-  // Phase 2: compute liveness of all virtual register.
+  // Phase 2: deconstruct SSA by inserting moves in successors and the headers
+  // of blocks containing phis.
+  void ResolvePhis();
+
+  // Phase 3: compute liveness of all virtual register.
   void BuildLiveRanges();
   bool ExistsUseWithoutDefinition();
 
-  // Phase 3: compute register assignments.
+  // Phase 4: compute register assignments.
   void AllocateGeneralRegisters();
   void AllocateDoubleRegisters();
 
-  // Phase 4: reassign spill splots for maximal reuse.
+  // Phase 5: reassign spill splots for maximal reuse.
   void ReuseSpillSlots();
 
-  // Phase 5: compute values for pointer maps.
+  // Phase 6: compute values for pointer maps.
   void PopulatePointerMaps();  // TODO(titzer): rename to PopulateReferenceMaps.
 
-  // Phase 6: reconnect split ranges with moves.
+  // Phase 7: reconnect split ranges with moves.
   void ConnectRanges();
 
-  // Phase 7: insert moves to connect ranges across basic blocks.
+  // Phase 8: insert moves to connect ranges across basic blocks.
   void ResolveControlFlow();
 
  private:
   int GetVirtualRegister() {
     int vreg = code()->NextVirtualRegister();
     if (vreg >= UnallocatedOperand::kMaxVirtualRegisters) {
       allocation_ok_ = false;
       // Maintain the invariant that we return something below the maximum.
       return 0;
     }
@@ skipping 27 matching lines @@
   BitVector* ComputeLiveOut(const InstructionBlock* block);
   void AddInitialIntervals(const InstructionBlock* block, BitVector* live_out);
   bool IsOutputRegisterOf(Instruction* instr, int index);
   bool IsOutputDoubleRegisterOf(Instruction* instr, int index);
   void ProcessInstructions(const InstructionBlock* block, BitVector* live);
   void MeetRegisterConstraints(const InstructionBlock* block);
   void MeetConstraintsBetween(Instruction* first, Instruction* second,
                               int gap_index);
   void MeetRegisterConstraintsForLastInstructionInBlock(
       const InstructionBlock* block);
-  void ProcessPhis(const InstructionBlock* block);
+  void ResolvePhis(const InstructionBlock* block);
 
   // Helper methods for building intervals.
   InstructionOperand* AllocateFixed(UnallocatedOperand* operand, int pos,
                                     bool is_tagged);
   LiveRange* LiveRangeFor(InstructionOperand* operand);
   void Define(LifetimePosition position, InstructionOperand* operand,
               InstructionOperand* hint);
   void Use(LifetimePosition block_start, LifetimePosition position,
            InstructionOperand* operand, InstructionOperand* hint);
   void AddConstraintsGapMove(int index, InstructionOperand* from,
@@ skipping 129 matching lines @@
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(RegisterAllocator);
 };
 
 }
 }
 }  // namespace v8::internal::compiler
 
 #endif  // V8_REGISTER_ALLOCATOR_H_