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thirdparty/clang/include/llvm/CodeGen/DFAPacketizer.h

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+//=- llvm/CodeGen/DFAPacketizer.h - DFA Packetizer for VLIW ---*- C++ -*-=====//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// This class implements a deterministic finite automaton (DFA) based
+// packetizing mechanism for VLIW architectures. It provides APIs to
+// determine whether there exists a legal mapping of instructions to
+// functional unit assignments in a packet. The DFA is auto-generated from
+// the target's Schedule.td file.
+//
+// A DFA consists of 3 major elements: states, inputs, and transitions. For
+// the packetizing mechanism, the input is the set of instruction classes for
+// a target. The state models all possible combinations of functional unit
+// consumption for a given set of instructions in a packet. A transition
+// models the addition of an instruction to a packet. In the DFA constructed
+// by this class, if an instruction can be added to a packet, then a valid
+// transition exists from the corresponding state. Invalid transitions
+// indicate that the instruction cannot be added to the current packet.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_DFAPACKETIZER_H
+#define LLVM_CODEGEN_DFAPACKETIZER_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include <map>
+
+namespace llvm {
+
+class MCInstrDesc;
+class MachineInstr;
+class MachineLoopInfo;
+class MachineDominatorTree;
+class InstrItineraryData;
+class DefaultVLIWScheduler;
+class SUnit;
+
+class DFAPacketizer {
+private:
+  typedef std::pair<unsigned, unsigned> UnsignPair;
+  const InstrItineraryData *InstrItins;
+  int CurrentState;
+  const int (*DFAStateInputTable)[2];
+  const unsigned *DFAStateEntryTable;
+
+  // CachedTable is a map from <FromState, Input> to ToState.
+  DenseMap<UnsignPair, unsigned> CachedTable;
+
+  // ReadTable - Read the DFA transition table and update CachedTable.
+  void ReadTable(unsigned int state);
+
+public:
+  DFAPacketizer(const InstrItineraryData *I, const int (*SIT)[2],
+                const unsigned *SET);
+
+  // Reset the current state to make all resources available.
+  void clearResources() {
+    CurrentState = 0;
+  }
+
+  // canReserveResources - Check if the resources occupied by a MCInstrDesc
+  // are available in the current state.
+  bool canReserveResources(const llvm::MCInstrDesc *MID);
+
+  // reserveResources - Reserve the resources occupied by a MCInstrDesc and
+  // change the current state to reflect that change.
+  void reserveResources(const llvm::MCInstrDesc *MID);
+
+  // canReserveResources - Check if the resources occupied by a machine
+  // instruction are available in the current state.
+  bool canReserveResources(llvm::MachineInstr *MI);
+
+  // reserveResources - Reserve the resources occupied by a machine
+  // instruction and change the current state to reflect that change.
+  void reserveResources(llvm::MachineInstr *MI);
+
+  const InstrItineraryData *getInstrItins() const { return InstrItins; }
+};
+
+// VLIWPacketizerList - Implements a simple VLIW packetizer using DFA. The
+// packetizer works on machine basic blocks. For each instruction I in BB, the
+// packetizer consults the DFA to see if machine resources are available to
+// execute I. If so, the packetizer checks if I depends on any instruction J in
+// the current packet. If no dependency is found, I is added to current packet
+// and machine resource is marked as taken. If any dependency is found, a target
+// API call is made to prune the dependence.
+class VLIWPacketizerList {
+protected:
+  const TargetMachine &TM;
+  const MachineFunction &MF;
+  const TargetInstrInfo *TII;
+
+  // The VLIW Scheduler.
+  DefaultVLIWScheduler *VLIWScheduler;
+
+  // Vector of instructions assigned to the current packet.
+  std::vector<MachineInstr*> CurrentPacketMIs;
+  // DFA resource tracker.
+  DFAPacketizer *ResourceTracker;
+
+  // Generate MI -> SU map.
+  std::map<MachineInstr*, SUnit*> MIToSUnit;
+
+public:
+  VLIWPacketizerList(
+    MachineFunction &MF, MachineLoopInfo &MLI, MachineDominatorTree &MDT,
+    bool IsPostRA);
+
+  virtual ~VLIWPacketizerList();
+
+  // PacketizeMIs - Implement this API in the backend to bundle instructions.
+  void PacketizeMIs(MachineBasicBlock *MBB,
+                    MachineBasicBlock::iterator BeginItr,
+                    MachineBasicBlock::iterator EndItr);
+
+  // getResourceTracker - return ResourceTracker
+  DFAPacketizer *getResourceTracker() {return ResourceTracker;}
+
+  // addToPacket - Add MI to the current packet.
+  virtual MachineBasicBlock::iterator addToPacket(MachineInstr *MI) {
+    MachineBasicBlock::iterator MII = MI;
+    CurrentPacketMIs.push_back(MI);
+    ResourceTracker->reserveResources(MI);
+    return MII;
+  }
+
+  // endPacket - End the current packet.
+  void endPacket(MachineBasicBlock *MBB, MachineInstr *MI);
+
+  // initPacketizerState - perform initialization before packetizing
+  // an instruction. This function is supposed to be overrided by
+  // the target dependent packetizer.
+  virtual void initPacketizerState() { return; }
+
+  // ignorePseudoInstruction - Ignore bundling of pseudo instructions.
+  virtual bool ignorePseudoInstruction(MachineInstr *I,
+                                       MachineBasicBlock *MBB) {
+    return false;
+  }
+
+  // isSoloInstruction - return true if instruction MI can not be packetized
+  // with any other instruction, which means that MI itself is a packet.
+  virtual bool isSoloInstruction(MachineInstr *MI) {
+    return true;
+  }
+
+  // isLegalToPacketizeTogether - Is it legal to packetize SUI and SUJ
+  // together.
+  virtual bool isLegalToPacketizeTogether(SUnit *SUI, SUnit *SUJ) {
+    return false;
+  }
+
+  // isLegalToPruneDependencies - Is it legal to prune dependece between SUI
+  // and SUJ.
+  virtual bool isLegalToPruneDependencies(SUnit *SUI, SUnit *SUJ) {
+    return false;
+  }
+
+};
+}
+
+#endif