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More local spiller complexity!

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If local spiller optimization turns some instruction into an identity copy, it will be removed. If the output register happens to be dead (and source is obviously killed), transfer the kill / dead information to last use / def in the same MBB.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51306 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2008-05-20 08:13:21 +00:00
parent b0a6f62c9b
commit 7a0f1851ec
2 changed files with 84 additions and 0 deletions
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62
lib/CodeGen/VirtRegMap.cpp
View File

@ -302,6 +302,7 @@ namespace {
MachineRegisterInfo *RegInfo;
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
DenseMap<MachineInstr*, unsigned> DistanceMap;
public:
bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
RegInfo = &MF.getRegInfo();
@ -333,6 +334,9 @@ namespace {
return true;
}
private:
void TransferDeadness(MachineBasicBlock *MBB, unsigned CurDist,
unsigned Reg, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps);
bool PrepForUnfoldOpti(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
std::vector<MachineInstr*> &MaybeDeadStores,
@ -943,6 +947,7 @@ bool LocalSpiller::PrepForUnfoldOpti(MachineBasicBlock &MBB,
VRM.assignVirt2Phys(UnfoldVR, UnfoldPR);
VRM.virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef);
MII = MBB.insert(MII, FoldedMI);
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
return true;
@ -1026,6 +1031,49 @@ void LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
++NumStores;
}
/// TransferDeadness - A identity copy definition is dead and it's being
/// removed. Find the last def or use and mark it as dead / kill.
void LocalSpiller::TransferDeadness(MachineBasicBlock *MBB, unsigned CurDist,
unsigned Reg, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps) {
int LastUDDist = -1;
MachineInstr *LastUDMI = NULL;
for (MachineRegisterInfo::reg_iterator RI = RegInfo->reg_begin(Reg),
RE = RegInfo->reg_end(); RI != RE; ++RI) {
MachineInstr *UDMI = &*RI;
if (UDMI->getParent() != MBB)
continue;
DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UDMI);
if (DI == DistanceMap.end() || DI->second > CurDist)
continue;
if ((int)DI->second < LastUDDist)
continue;
LastUDDist = DI->second;
LastUDMI = UDMI;
}
if (LastUDMI) {
const TargetInstrDesc &TID = LastUDMI->getDesc();
MachineOperand *LastUD = NULL;
for (unsigned i = 0, e = LastUDMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = LastUDMI->getOperand(i);
if (!MO.isRegister() || MO.getReg() != Reg)
continue;
if (!LastUD || (LastUD->isUse() && MO.isDef()))
LastUD = &MO;
if (TID.getOperandConstraint(i, TOI::TIED_TO) != -1)
return;
}
if (LastUD->isDef())
LastUD->setIsDead();
else {
LastUD->setIsKill();
RegKills.set(Reg);
KillOps[Reg] = LastUD;
}
}
}
/// rewriteMBB - Keep track of which spills are available even after the
/// register allocator is done with them. If possible, avid reloading vregs.
void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
@ -1054,6 +1102,8 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
std::vector<MachineOperand*> KillOps;
KillOps.resize(TRI->getNumRegs(), NULL);
unsigned Dist = 0;
DistanceMap.clear();
for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
MII != E; ) {
MachineBasicBlock::iterator NextMII = MII; ++NextMII;
@ -1431,6 +1481,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
InvalidateKill(InReg, RegKills, KillOps);
}
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
@ -1442,6 +1493,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
if (PhysReg &&
TII->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)) {
MBB.insert(MII, NewMIs[0]);
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
@ -1476,6 +1528,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
NewStore = NewMIs[1];
MBB.insert(MII, NewStore);
VRM.addSpillSlotUse(SS, NewStore);
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
@ -1549,6 +1602,13 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
SmallVector<unsigned, 2> KillRegs;
InvalidateKills(MI, RegKills, KillOps, &KillRegs);
if (MO.isDead() && !KillRegs.empty()) {
assert(KillRegs[0] == Dst);
// Last def is now dead.
TransferDeadness(&MBB, Dist, Src, RegKills, KillOps);
}
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
@ -1626,6 +1686,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
InvalidateKills(MI, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
@ -1636,6 +1697,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
}
}
ProcessNextInst:
DistanceMap.insert(std::make_pair(&MI, Dist++));
if (!Erased && !BackTracked) {
for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II)
UpdateKills(*II, RegKills, KillOps);

22
test/CodeGen/ARM/2008-05-19-ScavengerAssert.ll Normal file
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@ -0,0 +1,22 @@
; RUN: llvm-as < %s | llc -mtriple=arm-apple-darwin
%struct.Decoders = type { i32**, i16***, i16****, i16***, i16**, i8**, i8** }
@decoders = external global %struct.Decoders ; <%struct.Decoders*> [#uses=1]
declare i8* @calloc(i32, i32)
declare fastcc i32 @get_mem2Dint(i32***, i32, i32)
define fastcc void @init_global_buffers() nounwind {
entry:
%tmp151 = tail call fastcc i32 @get_mem2Dint( i32*** getelementptr (%struct.Decoders* @decoders, i32 0, i32 0), i32 16, i32 16 ) ; <i32> [#uses=1]
%tmp158 = tail call i8* @calloc( i32 0, i32 4 ) ; <i8*> [#uses=0]
br i1 false, label %cond_true166, label %bb190.preheader
bb190.preheader: ; preds = %entry
%memory_size.3555 = add i32 0, %tmp151 ; <i32> [#uses=0]
unreachable
cond_true166: ; preds = %entry
unreachable
}