1 //=- llvm/CodeGen/DFAPacketizer.h - DFA Packetizer for VLIW ---*- C++ -*-=====//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 // This class implements a deterministic finite automaton (DFA) based
10 // packetizing mechanism for VLIW architectures. It provides APIs to
11 // determine whether there exists a legal mapping of instructions to
12 // functional unit assignments in a packet. The DFA is auto-generated from
13 // the target's Schedule.td file.
14 //
15 // A DFA consists of 3 major elements: states, inputs, and transitions. For
16 // the packetizing mechanism, the input is the set of instruction classes for
17 // a target. The state models all possible combinations of functional unit
18 // consumption for a given set of instructions in a packet. A transition
19 // models the addition of an instruction to a packet. In the DFA constructed
20 // by this class, if an instruction can be added to a packet, then a valid
21 // transition exists from the corresponding state. Invalid transitions
22 // indicate that the instruction cannot be added to the current packet.
23 //
24 //===----------------------------------------------------------------------===//
25 
26 #ifndef LLVM_CODEGEN_DFAPACKETIZER_H
27 #define LLVM_CODEGEN_DFAPACKETIZER_H
28 
29 #include "llvm/ADT/DenseMap.h"
30 
31 namespace llvm {
32 
33 class MCInstrDesc;
34 class MachineInstr;
35 class InstrItineraryData;
36 
37 class DFAPacketizer {
38 private:
39   typedef std::pair<unsigned, unsigned> UnsignPair;
40   const InstrItineraryData *InstrItins;
41   int CurrentState;
42   const int (*DFAStateInputTable)[2];
43   const unsigned *DFAStateEntryTable;
44 
45   // CachedTable is a map from <FromState, Input> to ToState.
46   DenseMap<UnsignPair, unsigned> CachedTable;
47 
48   // ReadTable - Read the DFA transition table and update CachedTable.
49   void ReadTable(unsigned int state);
50 
51 public:
52   DFAPacketizer(const InstrItineraryData *I, const int (*SIT)[2],
53                 const unsigned *SET);
54 
55   // Reset the current state to make all resources available.
56   void clearResources() {
57     CurrentState = 0;
58   }
59 
60   // canReserveResources - Check if the resources occupied by a MCInstrDesc
61   // are available in the current state.
62   bool canReserveResources(const llvm::MCInstrDesc *MID);
63 
64   // reserveResources - Reserve the resources occupied by a MCInstrDesc and
65   // change the current state to reflect that change.
66   void reserveResources(const llvm::MCInstrDesc *MID);
67 
68   // canReserveResources - Check if the resources occupied by a machine
69   // instruction are available in the current state.
70   bool canReserveResources(llvm::MachineInstr *MI);
71 
72   // reserveResources - Reserve the resources occupied by a machine
73   // instruction and change the current state to reflect that change.
74   void reserveResources(llvm::MachineInstr *MI);
75 };
76 }
77 
78 #endif
79