LiveRangeEdit.cpp revision a17768f5822ab62bc18608e5ba473187bf726b84 
1//===--- LiveRangeEdit.cpp - Basic tools for editing a register live range --===//
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// The LiveRangeEdit class represents changes done to a virtual register when it
11// is spilled or split.
12//===----------------------------------------------------------------------===//
13
14#include "LiveRangeEdit.h"
15#include "VirtRegMap.h"
16#include "llvm/CodeGen/LiveIntervalAnalysis.h"
17#include "llvm/CodeGen/MachineRegisterInfo.h"
18
19using namespace llvm;
20
21LiveInterval &LiveRangeEdit::create(MachineRegisterInfo &mri,
22                                    LiveIntervals &lis,
23                                    VirtRegMap &vrm) {
24  const TargetRegisterClass *RC = mri.getRegClass(parent_.reg);
25  unsigned VReg = mri.createVirtualRegister(RC);
26  vrm.grow();
27  LiveInterval &li = lis.getOrCreateInterval(VReg);
28  newRegs_.push_back(&li);
29  return li;
30}
31
32/// allUsesAvailableAt - Return true if all registers used by OrigMI at
33/// OrigIdx are also available with the same value at UseIdx.
34bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
35                                       SlotIndex OrigIdx,
36                                       SlotIndex UseIdx,
37                                       LiveIntervals &lis) {
38  OrigIdx = OrigIdx.getUseIndex();
39  UseIdx = UseIdx.getUseIndex();
40  for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) {
41    const MachineOperand &MO = OrigMI->getOperand(i);
42    if (!MO.isReg() || !MO.getReg() || MO.getReg() == getReg())
43      continue;
44    // Reserved registers are OK.
45    if (MO.isUndef() || !lis.hasInterval(MO.getReg()))
46      continue;
47    // We don't want to move any defs.
48    if (MO.isDef())
49      return false;
50    // We cannot depend on virtual registers in uselessRegs_.
51    for (unsigned ui = 0, ue = uselessRegs_.size(); ui != ue; ++ui)
52      if (uselessRegs_[ui]->reg == MO.getReg())
53        return false;
54
55    LiveInterval &li = lis.getInterval(MO.getReg());
56    const VNInfo *OVNI = li.getVNInfoAt(OrigIdx);
57    if (!OVNI)
58      continue;
59    if (OVNI != li.getVNInfoAt(UseIdx))
60      return false;
61  }
62  return true;
63}
64
65