LCOV - code coverage report
Current view: top level - src/compiler - instruction-scheduler.h (source / functions) Hit Total Coverage
Test: app.info Lines: 0 18 0.0 %
Date: 2017-04-26 Functions: 0 2 0.0 %

          Line data    Source code
       1             : // Copyright 2015 the V8 project authors. All rights reserved.
       2             : // Use of this source code is governed by a BSD-style license that can be
       3             : // found in the LICENSE file.
       4             : 
       5             : #ifndef V8_COMPILER_INSTRUCTION_SCHEDULER_H_
       6             : #define V8_COMPILER_INSTRUCTION_SCHEDULER_H_
       7             : 
       8             : #include "src/compiler/instruction.h"
       9             : #include "src/zone/zone-containers.h"
      10             : 
      11             : namespace v8 {
      12             : namespace internal {
      13             : namespace compiler {
      14             : 
      15             : // A set of flags describing properties of the instructions so that the
      16             : // scheduler is aware of dependencies between instructions.
      17             : enum ArchOpcodeFlags {
      18             :   kNoOpcodeFlags = 0,
      19             :   kIsBlockTerminator = 1,  // The instruction marks the end of a basic block
      20             :                            // e.g.: jump and return instructions.
      21             :   kHasSideEffect = 2,      // The instruction has some side effects (memory
      22             :                            // store, function call...)
      23             :   kIsLoadOperation = 4,    // The instruction is a memory load.
      24             :   kMayNeedDeoptCheck = 8,  // The instruction might be associated with a deopt
      25             :                            // check. This is the case of instruction which can
      26             :                            // blow up with particular inputs (e.g.: division by
      27             :                            // zero on Intel platforms).
      28             : };
      29             : 
      30             : class InstructionScheduler final : public ZoneObject {
      31             :  public:
      32             :   InstructionScheduler(Zone* zone, InstructionSequence* sequence);
      33             : 
      34             :   void StartBlock(RpoNumber rpo);
      35             :   void EndBlock(RpoNumber rpo);
      36             : 
      37             :   void AddInstruction(Instruction* instr);
      38             : 
      39             :   static bool SchedulerSupported();
      40             : 
      41             :  private:
      42             :   // A scheduling graph node.
      43             :   // Represent an instruction and their dependencies.
      44             :   class ScheduleGraphNode: public ZoneObject {
      45             :    public:
      46             :     ScheduleGraphNode(Zone* zone, Instruction* instr);
      47             : 
      48             :     // Mark the instruction represented by 'node' as a dependecy of this one.
      49             :     // The current instruction will be registered as an unscheduled predecessor
      50             :     // of 'node' (i.e. it must be scheduled before 'node').
      51             :     void AddSuccessor(ScheduleGraphNode* node);
      52             : 
      53             :     // Check if all the predecessors of this instruction have been scheduled.
      54             :     bool HasUnscheduledPredecessor() {
      55             :       return unscheduled_predecessors_count_ != 0;
      56             :     }
      57             : 
      58             :     // Record that we have scheduled one of the predecessors of this node.
      59             :     void DropUnscheduledPredecessor() {
      60             :       DCHECK(unscheduled_predecessors_count_ > 0);
      61           0 :       unscheduled_predecessors_count_--;
      62             :     }
      63             : 
      64             :     Instruction* instruction() { return instr_; }
      65             :     ZoneDeque<ScheduleGraphNode*>& successors() { return successors_; }
      66             :     int latency() const { return latency_; }
      67             : 
      68             :     int total_latency() const { return total_latency_; }
      69           0 :     void set_total_latency(int latency) { total_latency_ = latency; }
      70             : 
      71             :     int start_cycle() const { return start_cycle_; }
      72           0 :     void set_start_cycle(int start_cycle) { start_cycle_ = start_cycle; }
      73             : 
      74             :    private:
      75             :     Instruction* instr_;
      76             :     ZoneDeque<ScheduleGraphNode*> successors_;
      77             : 
      78             :     // Number of unscheduled predecessors for this node.
      79             :     int unscheduled_predecessors_count_;
      80             : 
      81             :     // Estimate of the instruction latency (the number of cycles it takes for
      82             :     // instruction to complete).
      83             :     int latency_;
      84             : 
      85             :     // The sum of all the latencies on the path from this node to the end of
      86             :     // the graph (i.e. a node with no successor).
      87             :     int total_latency_;
      88             : 
      89             :     // The scheduler keeps a nominal cycle count to keep track of when the
      90             :     // result of an instruction is available. This field is updated by the
      91             :     // scheduler to indicate when the value of all the operands of this
      92             :     // instruction will be available.
      93             :     int start_cycle_;
      94             :   };
      95             : 
      96             :   // Keep track of all nodes ready to be scheduled (i.e. all their dependencies
      97             :   // have been scheduled. Note that this class is inteded to be extended by
      98             :   // concrete implementation of the scheduling queue which define the policy
      99             :   // to pop node from the queue.
     100             :   class SchedulingQueueBase {
     101             :    public:
     102           0 :     explicit SchedulingQueueBase(InstructionScheduler* scheduler)
     103             :       : scheduler_(scheduler),
     104           0 :         nodes_(scheduler->zone()) {
     105             :     }
     106             : 
     107             :     void AddNode(ScheduleGraphNode* node);
     108             : 
     109             :     bool IsEmpty() const {
     110             :       return nodes_.empty();
     111             :     }
     112             : 
     113             :    protected:
     114             :     InstructionScheduler* scheduler_;
     115             :     ZoneLinkedList<ScheduleGraphNode*> nodes_;
     116             :   };
     117             : 
     118             :   // A scheduling queue which prioritize nodes on the critical path (we look
     119             :   // for the instruction with the highest latency on the path to reach the end
     120             :   // of the graph).
     121             :   class CriticalPathFirstQueue : public SchedulingQueueBase  {
     122             :    public:
     123             :     explicit CriticalPathFirstQueue(InstructionScheduler* scheduler)
     124             :       : SchedulingQueueBase(scheduler) { }
     125             : 
     126             :     // Look for the best candidate to schedule, remove it from the queue and
     127             :     // return it.
     128             :     ScheduleGraphNode* PopBestCandidate(int cycle);
     129             :   };
     130             : 
     131             :   // A queue which pop a random node from the queue to perform stress tests on
     132             :   // the scheduler.
     133             :   class StressSchedulerQueue : public SchedulingQueueBase  {
     134             :    public:
     135             :     explicit StressSchedulerQueue(InstructionScheduler* scheduler)
     136             :       : SchedulingQueueBase(scheduler) { }
     137             : 
     138             :     ScheduleGraphNode* PopBestCandidate(int cycle);
     139             : 
     140             :    private:
     141             :     Isolate *isolate() {
     142             :       return scheduler_->isolate();
     143             :     }
     144             :   };
     145             : 
     146             :   // Perform scheduling for the current block specifying the queue type to
     147             :   // use to determine the next best candidate.
     148             :   template <typename QueueType>
     149           0 :   void ScheduleBlock();
     150             : 
     151             :   // Return the scheduling properties of the given instruction.
     152             :   int GetInstructionFlags(const Instruction* instr) const;
     153             :   int GetTargetInstructionFlags(const Instruction* instr) const;
     154             : 
     155             :   // Return true if the instruction is a basic block terminator.
     156             :   bool IsBlockTerminator(const Instruction* instr) const;
     157             : 
     158             :   // Check whether the given instruction has side effects (e.g. function call,
     159             :   // memory store).
     160             :   bool HasSideEffect(const Instruction* instr) const {
     161           0 :     return (GetInstructionFlags(instr) & kHasSideEffect) != 0;
     162             :   }
     163             : 
     164             :   // Return true if the instruction is a memory load.
     165             :   bool IsLoadOperation(const Instruction* instr) const {
     166           0 :     return (GetInstructionFlags(instr) & kIsLoadOperation) != 0;
     167             :   }
     168             : 
     169             :   // Return true if this instruction is usually associated with a deopt check
     170             :   // to validate its input.
     171             :   bool MayNeedDeoptCheck(const Instruction* instr) const {
     172           0 :     return (GetInstructionFlags(instr) & kMayNeedDeoptCheck) != 0;
     173             :   }
     174             : 
     175             :   // Return true if the instruction cannot be moved before the last deopt
     176             :   // point we encountered.
     177           0 :   bool DependsOnDeoptimization(const Instruction* instr) const {
     178           0 :     return MayNeedDeoptCheck(instr) || instr->IsDeoptimizeCall() ||
     179           0 :            HasSideEffect(instr) || IsLoadOperation(instr);
     180             :   }
     181             : 
     182             :   // Identify nops used as a definition point for live-in registers at
     183             :   // function entry.
     184           0 :   bool IsFixedRegisterParameter(const Instruction* instr) const {
     185           0 :     return (instr->arch_opcode() == kArchNop) && (instr->OutputCount() == 1) &&
     186           0 :            (instr->OutputAt(0)->IsUnallocated()) &&
     187             :            (UnallocatedOperand::cast(instr->OutputAt(0))
     188           0 :                 ->HasFixedRegisterPolicy() ||
     189             :             UnallocatedOperand::cast(instr->OutputAt(0))
     190           0 :                 ->HasFixedFPRegisterPolicy());
     191             :   }
     192             : 
     193             :   void ComputeTotalLatencies();
     194             : 
     195             :   static int GetInstructionLatency(const Instruction* instr);
     196             : 
     197             :   Zone* zone() { return zone_; }
     198             :   InstructionSequence* sequence() { return sequence_; }
     199           0 :   Isolate* isolate() { return sequence()->isolate(); }
     200             : 
     201             :   Zone* zone_;
     202             :   InstructionSequence* sequence_;
     203             :   ZoneVector<ScheduleGraphNode*> graph_;
     204             : 
     205             :   // Last side effect instruction encountered while building the graph.
     206             :   ScheduleGraphNode* last_side_effect_instr_;
     207             : 
     208             :   // Set of load instructions encountered since the last side effect instruction
     209             :   // which will be added as predecessors of the next instruction with side
     210             :   // effects.
     211             :   ZoneVector<ScheduleGraphNode*> pending_loads_;
     212             : 
     213             :   // Live-in register markers are nop instructions which are emitted at the
     214             :   // beginning of a basic block so that the register allocator will find a
     215             :   // defining instruction for live-in values. They must not be moved.
     216             :   // All these nops are chained together and added as a predecessor of every
     217             :   // other instructions in the basic block.
     218             :   ScheduleGraphNode* last_live_in_reg_marker_;
     219             : 
     220             :   // Last deoptimization instruction encountered while building the graph.
     221             :   ScheduleGraphNode* last_deopt_;
     222             : 
     223             :   // Keep track of definition points for virtual registers. This is used to
     224             :   // record operand dependencies in the scheduling graph.
     225             :   ZoneMap<int32_t, ScheduleGraphNode*> operands_map_;
     226             : };
     227             : 
     228             : }  // namespace compiler
     229             : }  // namespace internal
     230             : }  // namespace v8
     231             : 
     232             : #endif  // V8_COMPILER_INSTRUCTION_SCHEDULER_H_

Generated by: LCOV version 1.10