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Teach the spiller to commute instructions in order to fold a reload. This hits 410 times on 444.namd and 122 times on 252.eon.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52266 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2008-06-13 23:58:02 +00:00
parent 6100119620
commit 87bb991aa8
2 changed files with 167 additions and 18 deletions
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143
lib/CodeGen/VirtRegMap.cpp
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@ -36,16 +36,17 @@
#include <algorithm>
using namespace llvm;
STATISTIC(NumSpills, "Number of register spills");
STATISTIC(NumPSpills,"Number of physical register spills");
STATISTIC(NumReMats, "Number of re-materialization");
STATISTIC(NumDRM , "Number of re-materializable defs elided");
STATISTIC(NumStores, "Number of stores added");
STATISTIC(NumLoads , "Number of loads added");
STATISTIC(NumReused, "Number of values reused");
STATISTIC(NumDSE , "Number of dead stores elided");
STATISTIC(NumDCE , "Number of copies elided");
STATISTIC(NumDSS , "Number of dead spill slots removed");
STATISTIC(NumSpills , "Number of register spills");
STATISTIC(NumPSpills ,"Number of physical register spills");
STATISTIC(NumReMats , "Number of re-materialization");
STATISTIC(NumDRM , "Number of re-materializable defs elided");
STATISTIC(NumStores , "Number of stores added");
STATISTIC(NumLoads , "Number of loads added");
STATISTIC(NumReused , "Number of values reused");
STATISTIC(NumDSE , "Number of dead stores elided");
STATISTIC(NumDCE , "Number of copies elided");
STATISTIC(NumDSS , "Number of dead spill slots removed");
STATISTIC(NumCommutes, "Number of instructions commuted");
namespace {
enum SpillerName { simple, local };
@ -356,6 +357,13 @@ namespace {
AvailableSpills &Spills, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM);
bool CommuteToFoldReload(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
unsigned VirtReg, unsigned SrcReg, int SS,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
const TargetRegisterInfo *TRI,
VirtRegMap &VRM);
void SpillRegToStackSlot(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
int Idx, unsigned PhysReg, int StackSlot,
@ -874,12 +882,12 @@ namespace {
/// This enables unfolding optimization for a subsequent instruction which will
/// also eliminate the newly introduced store instruction.
bool LocalSpiller::PrepForUnfoldOpti(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
MachineBasicBlock::iterator &MII,
std::vector<MachineInstr*> &MaybeDeadStores,
AvailableSpills &Spills,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
AvailableSpills &Spills,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
MachineFunction &MF = *MBB.getParent();
MachineInstr &MI = *MII;
unsigned UnfoldedOpc = 0;
@ -971,6 +979,97 @@ bool LocalSpiller::PrepForUnfoldOpti(MachineBasicBlock &MBB,
return false;
}
/// CommuteToFoldReload -
/// Look for
/// r1 = load fi#1
/// r1 = op r1, r2<kill>
/// store r1, fi#1
///
/// If op is commutable and r2 is killed, then we can xform these to
/// r2 = op r2, fi#1
/// store r2, fi#1
bool LocalSpiller::CommuteToFoldReload(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
unsigned VirtReg, unsigned SrcReg, int SS,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
const TargetRegisterInfo *TRI,
VirtRegMap &VRM) {
if (MII == MBB.begin() || !MII->killsRegister(SrcReg))
return false;
MachineFunction &MF = *MBB.getParent();
MachineInstr &MI = *MII;
MachineBasicBlock::iterator DefMII = prior(MII);
MachineInstr *DefMI = DefMII;
const TargetInstrDesc &TID = DefMI->getDesc();
unsigned NewDstIdx;
if (DefMII != MBB.begin() &&
TID.isCommutable() &&
TII->CommuteChangesDestination(DefMI, NewDstIdx)) {
MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
unsigned NewReg = NewDstMO.getReg();
if (!NewDstMO.isKill() || TRI->regsOverlap(NewReg, SrcReg))
return false;
MachineInstr *ReloadMI = prior(DefMII);
int FrameIdx;
unsigned DestReg = TII->isLoadFromStackSlot(ReloadMI, FrameIdx);
if (DestReg != SrcReg || FrameIdx != SS)
return false;
int UseIdx = DefMI->findRegisterUseOperandIdx(DestReg, false);
if (UseIdx == -1)
return false;
int DefIdx = TID.getOperandConstraint(UseIdx, TOI::TIED_TO);
if (DefIdx == -1)
return false;
assert(DefMI->getOperand(DefIdx).isRegister() &&
DefMI->getOperand(DefIdx).getReg() == SrcReg);
// Now commute def instruction.
MachineInstr *CommutedMI = TII->commuteInstruction(DefMI);
if (!CommutedMI)
return false;
SmallVector<unsigned, 2> Ops;
Ops.push_back(NewDstIdx);
MachineInstr *FoldedMI = TII->foldMemoryOperand(MF, CommutedMI, Ops, SS);
if (!FoldedMI) {
if (CommutedMI == DefMI)
TII->commuteInstruction(CommutedMI);
else
MBB.erase(CommutedMI);
return false;
}
VRM.addSpillSlotUse(SS, FoldedMI);
VRM.virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef);
// Insert new def MI and spill MI.
const TargetRegisterClass* RC = MF.getRegInfo().getRegClass(VirtReg);
TII->storeRegToStackSlot(MBB, MI, NewReg, true, SS, RC);
MII = prior(MII);
MachineInstr *StoreMI = MII;
VRM.addSpillSlotUse(SS, StoreMI);
VRM.virtFolded(VirtReg, StoreMI, VirtRegMap::isMod);
MII = MBB.insert(MII, FoldedMI); // Update MII to backtrack.
// Delete all 3 old instructions.
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
if (CommutedMI != DefMI)
MBB.erase(CommutedMI);
InvalidateKills(*DefMI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(DefMI);
MBB.erase(DefMI);
InvalidateKills(*ReloadMI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(ReloadMI);
MBB.erase(ReloadMI);
++NumCommutes;
return true;
}
return false;
}
/// findSuperReg - Find the SubReg's super-register of given register class
/// where its SubIdx sub-register is SubReg.
static unsigned findSuperReg(const TargetRegisterClass *RC, unsigned SubReg,
@ -1587,15 +1686,23 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
assert(TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
"Src hasn't been allocated yet?");
if (CommuteToFoldReload(MBB, MII, VirtReg, SrcReg, StackSlot,
RegKills, KillOps, TRI, VRM)) {
NextMII = next(MII);
BackTracked = true;
goto ProcessNextInst;
}
// Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
// this as a potentially dead store in case there is a subsequent
// store into the stack slot without a read from it.
MaybeDeadStores[StackSlot] = &MI;
// If the stack slot value was previously available in some other
// register, change it now. Otherwise, make the register available,
// in PhysReg.
Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
// register, change it now. Otherwise, make the register
// available in PhysReg.
Spills.addAvailable(StackSlot, &MI, SrcReg, false/*!clobber*/);
}
}
}