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223 lines
8.2 KiB
C++
223 lines
8.2 KiB
C++
//===- llvm/CodeGen/DFAPacketizer.h - DFA Packetizer for VLIW ---*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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// This class implements a deterministic finite automaton (DFA) based
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// packetizing mechanism for VLIW architectures. It provides APIs to
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// determine whether there exists a legal mapping of instructions to
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// functional unit assignments in a packet. The DFA is auto-generated from
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// the target's Schedule.td file.
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//
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// A DFA consists of 3 major elements: states, inputs, and transitions. For
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// the packetizing mechanism, the input is the set of instruction classes for
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// a target. The state models all possible combinations of functional unit
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// consumption for a given set of instructions in a packet. A transition
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// models the addition of an instruction to a packet. In the DFA constructed
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// by this class, if an instruction can be added to a packet, then a valid
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// transition exists from the corresponding state. Invalid transitions
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// indicate that the instruction cannot be added to the current packet.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_DFAPACKETIZER_H
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#define LLVM_CODEGEN_DFAPACKETIZER_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/ScheduleDAGMutation.h"
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#include <cstdint>
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#include <map>
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#include <memory>
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#include <utility>
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#include <vector>
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namespace llvm {
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class DefaultVLIWScheduler;
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class InstrItineraryData;
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class MachineFunction;
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class MachineInstr;
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class MachineLoopInfo;
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class MCInstrDesc;
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class SUnit;
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class TargetInstrInfo;
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// --------------------------------------------------------------------
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// Definitions shared between DFAPacketizer.cpp and DFAPacketizerEmitter.cpp
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// DFA_MAX_RESTERMS * DFA_MAX_RESOURCES must fit within sizeof DFAInput.
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// This is verified in DFAPacketizer.cpp:DFAPacketizer::DFAPacketizer.
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//
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// e.g. terms x resource bit combinations that fit in uint32_t:
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// 4 terms x 8 bits = 32 bits
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// 3 terms x 10 bits = 30 bits
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// 2 terms x 16 bits = 32 bits
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//
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// e.g. terms x resource bit combinations that fit in uint64_t:
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// 8 terms x 8 bits = 64 bits
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// 7 terms x 9 bits = 63 bits
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// 6 terms x 10 bits = 60 bits
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// 5 terms x 12 bits = 60 bits
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// 4 terms x 16 bits = 64 bits <--- current
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// 3 terms x 21 bits = 63 bits
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// 2 terms x 32 bits = 64 bits
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//
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#define DFA_MAX_RESTERMS 4 // The max # of AND'ed resource terms.
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#define DFA_MAX_RESOURCES 16 // The max # of resource bits in one term.
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using DFAInput = uint64_t;
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using DFAStateInput = int64_t;
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#define DFA_TBLTYPE "int64_t" // For generating DFAStateInputTable.
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// --------------------------------------------------------------------
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class DFAPacketizer {
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private:
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using UnsignPair = std::pair<unsigned, DFAInput>;
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const InstrItineraryData *InstrItins;
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int CurrentState = 0;
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const DFAStateInput (*DFAStateInputTable)[2];
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const unsigned *DFAStateEntryTable;
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// CachedTable is a map from <FromState, Input> to ToState.
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DenseMap<UnsignPair, unsigned> CachedTable;
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// Read the DFA transition table and update CachedTable.
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void ReadTable(unsigned state);
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public:
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DFAPacketizer(const InstrItineraryData *I, const DFAStateInput (*SIT)[2],
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const unsigned *SET);
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// Reset the current state to make all resources available.
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void clearResources() {
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CurrentState = 0;
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}
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// Return the DFAInput for an instruction class.
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DFAInput getInsnInput(unsigned InsnClass);
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// Return the DFAInput for an instruction class input vector.
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static DFAInput getInsnInput(const std::vector<unsigned> &InsnClass);
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// Check if the resources occupied by a MCInstrDesc are available in
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// the current state.
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bool canReserveResources(const MCInstrDesc *MID);
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// Reserve the resources occupied by a MCInstrDesc and change the current
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// state to reflect that change.
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void reserveResources(const MCInstrDesc *MID);
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// Check if the resources occupied by a machine instruction are available
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// in the current state.
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bool canReserveResources(MachineInstr &MI);
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// Reserve the resources occupied by a machine instruction and change the
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// current state to reflect that change.
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void reserveResources(MachineInstr &MI);
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const InstrItineraryData *getInstrItins() const { return InstrItins; }
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};
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// VLIWPacketizerList implements a simple VLIW packetizer using DFA. The
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// packetizer works on machine basic blocks. For each instruction I in BB,
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// the packetizer consults the DFA to see if machine resources are available
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// to execute I. If so, the packetizer checks if I depends on any instruction
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// in the current packet. If no dependency is found, I is added to current
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// packet and the machine resource is marked as taken. If any dependency is
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// found, a target API call is made to prune the dependence.
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class VLIWPacketizerList {
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protected:
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MachineFunction &MF;
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const TargetInstrInfo *TII;
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AliasAnalysis *AA;
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// The VLIW Scheduler.
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DefaultVLIWScheduler *VLIWScheduler;
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// Vector of instructions assigned to the current packet.
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std::vector<MachineInstr*> CurrentPacketMIs;
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// DFA resource tracker.
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DFAPacketizer *ResourceTracker;
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// Map: MI -> SU.
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std::map<MachineInstr*, SUnit*> MIToSUnit;
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public:
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// The AliasAnalysis parameter can be nullptr.
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VLIWPacketizerList(MachineFunction &MF, MachineLoopInfo &MLI,
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AliasAnalysis *AA);
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virtual ~VLIWPacketizerList();
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// Implement this API in the backend to bundle instructions.
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void PacketizeMIs(MachineBasicBlock *MBB,
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MachineBasicBlock::iterator BeginItr,
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MachineBasicBlock::iterator EndItr);
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// Return the ResourceTracker.
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DFAPacketizer *getResourceTracker() {return ResourceTracker;}
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// addToPacket - Add MI to the current packet.
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virtual MachineBasicBlock::iterator addToPacket(MachineInstr &MI) {
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CurrentPacketMIs.push_back(&MI);
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ResourceTracker->reserveResources(MI);
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return MI;
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}
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// End the current packet and reset the state of the packetizer.
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// Overriding this function allows the target-specific packetizer
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// to perform custom finalization.
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virtual void endPacket(MachineBasicBlock *MBB,
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MachineBasicBlock::iterator MI);
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// Perform initialization before packetizing an instruction. This
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// function is supposed to be overrided by the target dependent packetizer.
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virtual void initPacketizerState() {}
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// Check if the given instruction I should be ignored by the packetizer.
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virtual bool ignorePseudoInstruction(const MachineInstr &I,
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const MachineBasicBlock *MBB) {
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return false;
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}
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// Return true if instruction MI can not be packetized with any other
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// instruction, which means that MI itself is a packet.
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virtual bool isSoloInstruction(const MachineInstr &MI) { return true; }
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// Check if the packetizer should try to add the given instruction to
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// the current packet. One reasons for which it may not be desirable
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// to include an instruction in the current packet could be that it
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// would cause a stall.
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// If this function returns "false", the current packet will be ended,
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// and the instruction will be added to the next packet.
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virtual bool shouldAddToPacket(const MachineInstr &MI) { return true; }
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// Check if it is legal to packetize SUI and SUJ together.
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virtual bool isLegalToPacketizeTogether(SUnit *SUI, SUnit *SUJ) {
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return false;
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}
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// Check if it is legal to prune dependece between SUI and SUJ.
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virtual bool isLegalToPruneDependencies(SUnit *SUI, SUnit *SUJ) {
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return false;
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}
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// Add a DAG mutation to be done before the packetization begins.
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void addMutation(std::unique_ptr<ScheduleDAGMutation> Mutation);
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bool alias(const MachineInstr &MI1, const MachineInstr &MI2,
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bool UseTBAA = true) const;
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private:
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bool alias(const MachineMemOperand &Op1, const MachineMemOperand &Op2,
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bool UseTBAA = true) const;
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};
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} // end namespace llvm
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#endif // LLVM_CODEGEN_DFAPACKETIZER_H
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