path: root/lib/CodeGen/SplitKit.cpp

//===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the SplitAnalysis class as well as mutator functions for
// live range splitting.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "splitter"
#include "SplitKit.h"
#include "VirtRegMap.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"

using namespace llvm;

static cl::opt<bool>
AllowSplit("spiller-splits-edges",
           cl::desc("Allow critical edge splitting during spilling"));

//===----------------------------------------------------------------------===//
//                                 Split Analysis
//===----------------------------------------------------------------------===//

SplitAnalysis::SplitAnalysis(const MachineFunction &mf,
                             const LiveIntervals &lis,
                             const MachineLoopInfo &mli)
  : mf_(mf),
    lis_(lis),
    loops_(mli),
    tii_(*mf.getTarget().getInstrInfo()),
    curli_(0) {}

void SplitAnalysis::clear() {
  usingInstrs_.clear();
  usingBlocks_.clear();
  usingLoops_.clear();
  curli_ = 0;
}

bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) {
  MachineBasicBlock *T, *F;
  SmallVector<MachineOperand, 4> Cond;
  return !tii_.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond);
}

/// analyzeUses - Count instructions, basic blocks, and loops using curli.
void SplitAnalysis::analyzeUses() {
  const MachineRegisterInfo &MRI = mf_.getRegInfo();
  for (MachineRegisterInfo::reg_iterator I = MRI.reg_begin(curli_->reg);
       MachineInstr *MI = I.skipInstruction();) {
    if (MI->isDebugValue() || !usingInstrs_.insert(MI))
      continue;
    MachineBasicBlock *MBB = MI->getParent();
    if (usingBlocks_[MBB]++)
      continue;
    if (MachineLoop *Loop = loops_.getLoopFor(MBB))
      usingLoops_[Loop]++;
  }
  DEBUG(dbgs() << "  counted "
               << usingInstrs_.size() << " instrs, "
               << usingBlocks_.size() << " blocks, "
               << usingLoops_.size()  << " loops.\n");
}

/// removeUse - Update statistics by noting that MI no longer uses curli.
void SplitAnalysis::removeUse(const MachineInstr *MI) {
  if (!usingInstrs_.erase(MI))
    return;

  // Decrement MBB count.
  const MachineBasicBlock *MBB = MI->getParent();
  BlockCountMap::iterator bi = usingBlocks_.find(MBB);
  assert(bi != usingBlocks_.end() && "MBB missing");
  assert(bi->second && "0 count in map");
  if (--bi->second)
    return;
  // No more uses in MBB.
  usingBlocks_.erase(bi);

  // Decrement loop count.
  MachineLoop *Loop = loops_.getLoopFor(MBB);
  if (!Loop)
    return;
  LoopCountMap::iterator li = usingLoops_.find(Loop);
  assert(li != usingLoops_.end() && "Loop missing");
  assert(li->second && "0 count in map");
  if (--li->second)
    return;
  // No more blocks in Loop.
  usingLoops_.erase(li);
}

// Get three sets of basic blocks surrounding a loop: Blocks inside the loop,
// predecessor blocks, and exit blocks.
void SplitAnalysis::getLoopBlocks