//===-- PreAllocSplitting.cpp - Pre-allocation Interval Spltting Pass. ----===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the machine instruction level pre-register allocation
// live interval splitting pass. It finds live interval barriers, i.e.
// instructions which will kill all physical registers in certain register
// classes, and split all live intervals which cross the barrier.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "pre-alloc-split"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegisterCoalescer.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
using namespace llvm;

namespace {
  class VISIBILITY_HIDDEN PreAllocSplitting : public MachineFunctionPass {
    // ProcessedBarriers - Register live interval barriers that have already
    // been processed.
    SmallPtrSet<MachineInstr*, 16> ProcessedBarriers;

    // ActiveBarriers - Register live interval barriers that are currently
    // being processed.
    SmallSet<unsigned, 16> ActiveBarriers;
  public:
    static char ID;
    PreAllocSplitting() : MachineFunctionPass(&ID) {}

    virtual bool runOnMachineFunction(MachineFunction &MF);

    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
      AU.addRequired<LiveIntervals>();
      AU.addPreserved<LiveIntervals>();
      AU.addPreserved<MachineLoopInfo>();
      AU.addPreserved<RegisterCoalescer>();
      if (StrongPHIElim)
        AU.addPreservedID(StrongPHIEliminationID);
      else
        AU.addPreservedID(PHIEliminationID);
      AU.addPreservedID(TwoAddressInstructionPassID);
      MachineFunctionPass::getAnalysisUsage(AU);
    }
    
    virtual void releaseMemory() {
      ProcessedBarriers.clear();
      ActiveBarriers.clear();
    }

    virtual const char *getPassName() const {
      return "Pre-Register Allocaton Live Interval Splitting";
    }
  };
} // end anonymous namespace

char PreAllocSplitting::ID = 0;

static RegisterPass<PreAllocSplitting>
X("pre-alloc-splitting", "Pre-Register Allocation Live Interval Splitting");

const PassInfo *const llvm::PreAllocSplittingID = &X;

bool PreAllocSplitting::runOnMachineFunction(MachineFunction &MF) {
  return false;
}