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//===--- LiveRangeEdit.cpp - Basic tools for editing a register live range --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// The LiveRangeEdit class represents changes done to a virtual register when it
// is spilled or split.
//===----------------------------------------------------------------------===//
#include "LiveRangeEdit.h"
#include "VirtRegMap.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
LiveInterval &LiveRangeEdit::create(MachineRegisterInfo &mri,
LiveIntervals &lis,
VirtRegMap &vrm) {
const TargetRegisterClass *RC = mri.getRegClass(getReg());
unsigned VReg = mri.createVirtualRegister(RC);
vrm.grow();
vrm.setIsSplitFromReg(VReg, vrm.getOriginal(getReg()));
LiveInterval &li = lis.getOrCreateInterval(VReg);
newRegs_.push_back(&li);
return li;
}
void LiveRangeEdit::scanRemattable(LiveIntervals &lis,
const TargetInstrInfo &tii,
AliasAnalysis *aa) {
for (LiveInterval::vni_iterator I = parent_.vni_begin(),
E = parent_.vni_end(); I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused())
continue;
MachineInstr *DefMI = lis.getInstructionFromIndex(VNI->def);
if (!DefMI)
continue;
if (tii.isTriviallyReMaterializable(DefMI, aa))
remattable_.insert(VNI);
}
scannedRemattable_ = true;
}
bool LiveRangeEdit::anyRematerializable(LiveIntervals &lis,
const TargetInstrInfo &tii,
AliasAnalysis *aa) {
if (!scannedRemattable_)
scanRemattable(lis, tii, aa);
return !remattable_.empty();
}
/// allUsesAvailableAt - Return true if all registers used by OrigMI at
/// OrigIdx are also available with the same value at UseIdx.
bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
SlotIndex OrigIdx,
SlotIndex UseIdx,
LiveIntervals &lis) {
OrigIdx = OrigIdx.getUseIndex();
UseIdx = UseIdx.getUseIndex();
for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = OrigMI->getOperand(i);
if (!MO.isReg() || !MO.getReg() || MO.getReg() == getReg())
continue;
// Reserved registers are OK.
if (MO.isUndef() || !lis.hasInterval(MO.getReg()))
continue;
// We don't want to move any defs.
if (MO.isDef())
return false;
// We cannot depend on virtual registers in uselessRegs_.
if (uselessRegs_)
for (unsigned ui = 0, ue = uselessRegs_->size(); ui != ue; ++ui)
if ((*uselessRegs_)[ui]->reg == MO.getReg())
return false;
LiveInterval &li = lis.getInterval(MO.getReg());
const VNInfo *OVNI = li.getVNInfoAt(OrigIdx);
if (!OVNI)
continue;
if (OVNI != li.getVNInfoAt(UseIdx))
return false;
}
return true;
}
bool LiveRangeEdit::canRematerializeAt(Remat &RM,
SlotIndex UseIdx,
bool cheapAsAMove,
LiveIntervals &lis) {
assert(scannedRemattable_ && "Call anyRematerializable first");
// Use scanRemattable info.
if (!remattable_.count(RM.ParentVNI))
return false;
// No defining instruction.
RM.OrigMI = lis.getInstructionFromIndex(RM.ParentVNI->def);
assert(RM.OrigMI && "Defining instruction for remattable value disappeared");
// If only cheap remats were requested, bail out early.
if (cheapAsAMove && !RM.OrigMI->getDesc().isAsCheapAsAMove())
return false;
// Verify that all used registers are available with the same values.
if (!allUsesAvailableAt(RM.OrigMI, RM.ParentVNI->def, UseIdx, lis))
return false;
return true;
}
SlotIndex LiveRangeEdit::rematerializeAt(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned DestReg,
const Remat &RM,
LiveIntervals &lis,
const TargetInstrInfo &tii,
const TargetRegisterInfo &tri) {
assert(RM.OrigMI && "Invalid remat");
tii.reMaterialize(MBB, MI, DestReg, 0, RM.OrigMI, tri);
rematted_.insert(RM.ParentVNI);
return lis.InsertMachineInstrInMaps(--MI).getDefIndex();
}
void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
LiveIntervals &LIS,
const TargetInstrInfo &TII) {
SetVector<LiveInterval*,
SmallVector<LiveInterval*, 8>,
SmallPtrSet<LiveInterval*, 8> > ToShrink;
for (;;) {
// Erase all dead defs.
while (!Dead.empty()) {
MachineInstr *MI = Dead.pop_back_val();
assert(MI->allDefsAreDead() && "Def isn't really dead");
// Never delete inline asm.
if (MI->isInlineAsm())
continue;
// Use the same criteria as DeadMachineInstructionElim.
bool SawStore = false;
if (!MI->isSafeToMove(&TII, 0, SawStore))
continue;
SlotIndex Idx = LIS.getInstructionIndex(MI).getDefIndex();
DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
// Check for live intervals that may shrink
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
if (!MOI->isReg())
continue;
unsigned Reg = MOI->getReg();
if (!TargetRegisterInfo::isVirtualRegister(Reg))
continue;
LiveInterval &LI = LIS.getInterval(Reg);
// Remove defined value.
if (MOI->isDef())
if (VNInfo *VNI = LI.getVNInfoAt(Idx))
LI.removeValNo(VNI);
// Shrink read registers.
if (MI->readsVirtualRegister(Reg))
ToShrink.insert(&LI);
}
if (delegate_)
delegate_->LRE_WillEraseInstruction(MI);
LIS.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
}
if (ToShrink.empty())
break;
// Shrink just one live interval. Then delete new dead defs.
LIS.shrinkToUses(ToShrink.back(), &Dead);
ToShrink.pop_back();
}
}
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