lib/CodeGen/PrologEpilogInserter.h

   1 //===-- PrologEpilogInserter.h - Prolog/Epilog code insertion -*- 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 //
  10 // This pass is responsible for finalizing the functions frame layout, saving
  11 // callee saved registers, and for emitting prolog & epilog code for the
  12 // function.
  13 //
  14 // This pass must be run after register allocation.  After this pass is
  15 // executed, it is illegal to construct MO_FrameIndex operands.
  16 //
  17 // This pass also implements a shrink wrapping variant of prolog/epilog
  18 // insertion.
  19 //
  20 //===----------------------------------------------------------------------===//
  21
  22 #ifndef LLVM_CODEGEN_PEI_H
  23 #define LLVM_CODEGEN_PEI_H
  24
  25 #include "llvm/CodeGen/Passes.h"
  26 #include "llvm/CodeGen/MachineFunctionPass.h"
  27 #include "llvm/CodeGen/MachineLoopInfo.h"
  28 #include "llvm/ADT/SparseBitVector.h"
  29 #include "llvm/ADT/DenseMap.h"
  30 #include "llvm/Target/TargetRegisterInfo.h"
  31
  32 namespace llvm {
  33   class RegScavenger;
  34   class MachineBasicBlock;
  35
  36   class PEI : public MachineFunctionPass {
  37   public:
  38     static char ID;
  39     PEI() : MachineFunctionPass(ID) {
  40       initializePEIPass(*PassRegistry::getPassRegistry());
  41     }
  42
  43     const char *getPassName() const {
  44       return "Prolog/Epilog Insertion & Frame Finalization";
  45     }
  46
  47     virtual void getAnalysisUsage(AnalysisUsage &AU) const;
  48
  49     /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
  50     /// frame indexes with appropriate references.
  51     ///
  52     bool runOnMachineFunction(MachineFunction &Fn);
  53
  54   private:
  55     RegScavenger *RS;
  56
  57     // MinCSFrameIndex, MaxCSFrameIndex - Keeps the range of callee saved
  58     // stack frame indexes.
  59     unsigned MinCSFrameIndex, MaxCSFrameIndex;
  60
  61     // Analysis info for spill/restore placement.
  62     // "CSR": "callee saved register".
  63
  64     // CSRegSet contains indices into the Callee Saved Register Info
  65     // vector built by calculateCalleeSavedRegisters() and accessed
  66     // via MF.getFrameInfo()->getCalleeSavedInfo().
  67     typedef SparseBitVector<> CSRegSet;
  68
  69     // CSRegBlockMap maps MachineBasicBlocks to sets of callee
  70     // saved register indices.
  71     typedef DenseMap<MachineBasicBlock*, CSRegSet> CSRegBlockMap;
  72
  73     // Set and maps for computing CSR spill/restore placement:
  74     //  used in function (UsedCSRegs)
  75     //  used in a basic block (CSRUsed)
  76     //  anticipatable in a basic block (Antic{In,Out})
  77     //  available in a basic block (Avail{In,Out})
  78     //  to be spilled at the entry to a basic block (CSRSave)
  79     //  to be restored at the end of a basic block (CSRRestore)
  80     CSRegSet UsedCSRegs;
  81     CSRegBlockMap CSRUsed;
  82     CSRegBlockMap AnticIn, AnticOut;
  83     CSRegBlockMap AvailIn, AvailOut;
  84     CSRegBlockMap CSRSave;
  85     CSRegBlockMap CSRRestore;
  86
  87     // Entry and return blocks of the current function.
  88     MachineBasicBlock* EntryBlock;
  89     SmallVector<MachineBasicBlock*, 4> ReturnBlocks;
  90
  91     // Map of MBBs to top level MachineLoops.
  92     DenseMap<MachineBasicBlock*, MachineLoop*> TLLoops;
  93
  94     // Flag to control shrink wrapping per-function:
  95     // may choose to skip shrink wrapping for certain
  96     // functions.
  97     bool ShrinkWrapThisFunction;
  98
  99     // Flag to control whether to use the register scavenger to resolve
 100     // frame index materialization registers. Set according to
 101     // TRI->requiresFrameIndexScavenging() for the curren function.
 102     bool FrameIndexVirtualScavenging;
 103
 104 #ifndef NDEBUG
 105     // Machine function handle.
 106     MachineFunction* MF;
 107
 108     // Flag indicating that the current function
 109     // has at least one "short" path in the machine
 110     // CFG from the entry block to an exit block.
 111     bool HasFastExitPath;
 112 #endif
 113
 114     bool calculateSets(MachineFunction &Fn);
 115     bool calcAnticInOut(MachineBasicBlock* MBB);
 116     bool calcAvailInOut(MachineBasicBlock* MBB);
 117     void calculateAnticAvail(MachineFunction &Fn);
 118     bool addUsesForMEMERegion(MachineBasicBlock* MBB,
 119                               SmallVector<MachineBasicBlock*, 4>& blks);
 120     bool addUsesForTopLevelLoops(SmallVector<MachineBasicBlock*, 4>& blks);
 121     bool calcSpillPlacements(MachineBasicBlock* MBB,
 122                              SmallVector<MachineBasicBlock*, 4> &blks,
 123                              CSRegBlockMap &prevSpills);
 124     bool calcRestorePlacements(MachineBasicBlock* MBB,
 125                                SmallVector<MachineBasicBlock*, 4> &blks,
 126                                CSRegBlockMap &prevRestores);
 127     void placeSpillsAndRestores(MachineFunction &Fn);
 128     void placeCSRSpillsAndRestores(MachineFunction &Fn);
 129     void calculateCallsInformation(MachineFunction &Fn);
 130     void calculateCalleeSavedRegisters(MachineFunction &Fn);
 131     void insertCSRSpillsAndRestores(MachineFunction &Fn);
 132     void calculateFrameObjectOffsets(MachineFunction &Fn);
 133     void replaceFrameIndices(MachineFunction &Fn);
 134     void scavengeFrameVirtualRegs(MachineFunction &Fn);
 135     void insertPrologEpilogCode(MachineFunction &Fn);
 136
 137     // Initialize DFA sets, called before iterations.
 138     void clearAnticAvailSets();
 139     // Clear all sets constructed by shrink wrapping.
 140     void clearAllSets();
 141
 142     // Initialize all shrink wrapping data.
 143     void initShrinkWrappingInfo();
 144
 145     // Convienences for dealing with machine loops.
 146     MachineBasicBlock* getTopLevelLoopPreheader(MachineLoop* LP);
 147     MachineLoop* getTopLevelLoopParent(MachineLoop *LP);
 148
 149     // Propgate CSRs used in MBB to all MBBs of loop LP.
 150     void propagateUsesAroundLoop(MachineBasicBlock* MBB, MachineLoop* LP);
 151
 152     // Convenience for recognizing return blocks.
 153     bool isReturnBlock(MachineBasicBlock* MBB);
 154
 155 #ifndef NDEBUG
 156     // Debugging methods.
 157
 158     // Mark this function as having fast exit paths.
 159     void findFastExitPath();
 160
 161     // Verify placement of spills/restores.
 162     void verifySpillRestorePlacement();
 163
 164     std::string getBasicBlockName(const MachineBasicBlock* MBB);
 165     std::string stringifyCSRegSet(const CSRegSet& s);
 166     void dumpSet(const CSRegSet& s);
 167     void dumpUsed(MachineBasicBlock* MBB);
 168     void dumpAllUsed();
 169     void dumpSets(MachineBasicBlock* MBB);
 170     void dumpSets1(MachineBasicBlock* MBB);
 171     void dumpAllSets();
 172     void dumpSRSets();
 173 #endif
 174
 175   };
 176 } // End llvm namespace
 177 #endif