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Don't delete dead code in TwoAddressInstructionPass. 

This functionality was added before we started running
DeadMachineInstructionElim on all targets. It serves no purpose now.

llvm-svn: 161241
This commit is contained in:
Jakob Stoklund Olesen 2012-08-03 15:11:57 +00:00
parent a1529b6ca4
commit 47ac20d4d6
1 changed files with 0 additions and 104 deletions
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104
llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
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@ -55,7 +55,6 @@ STATISTIC(NumCommuted , "Number of instructions commuted to coalesce");
STATISTIC(NumAggrCommuted , "Number of instructions aggressively commuted");
STATISTIC(NumConvertedTo3Addr, "Number of instructions promoted to 3-address");
STATISTIC(Num3AddrSunk, "Number of 3-address instructions sunk");
STATISTIC(NumDeletes, "Number of dead instructions deleted");
STATISTIC(NumReSchedUps, "Number of instructions re-scheduled up");
STATISTIC(NumReSchedDowns, "Number of instructions re-scheduled down");
@ -112,14 +111,6 @@ namespace {
MachineFunction::iterator &mbbi,
unsigned RegA, unsigned RegB, unsigned Dist);
typedef std::pair<std::pair<unsigned, bool>, MachineInstr*> NewKill;
bool canUpdateDeletedKills(SmallVector<unsigned, 4> &Kills,
SmallVector<NewKill, 4> &NewKills,
MachineBasicBlock *MBB, unsigned Dist);
bool DeleteUnusedInstr(MachineBasicBlock::iterator &mi,
MachineBasicBlock::iterator &nmi,
MachineFunction::iterator &mbbi, unsigned Dist);
bool isDefTooClose(unsigned Reg, unsigned Dist,
MachineInstr *MI, MachineBasicBlock *MBB);
@ -731,92 +722,6 @@ void TwoAddressInstructionPass::ProcessCopy(MachineInstr *MI,
return;
}
/// isSafeToDelete - If the specified instruction does not produce any side
/// effects and all of its defs are dead, then it's safe to delete.
static bool isSafeToDelete(MachineInstr *MI,
const TargetInstrInfo *TII,
SmallVector<unsigned, 4> &Kills) {
if (MI->mayStore() || MI->isCall())
return false;
if (MI->isTerminator() || MI->hasUnmodeledSideEffects())
return false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg())
continue;
if (MO.isDef() && !MO.isDead())
return false;
if (MO.isUse() && MO.isKill())
Kills.push_back(MO.getReg());
}
return true;
}
/// canUpdateDeletedKills - Check if all the registers listed in Kills are
/// killed by instructions in MBB preceding the current instruction at
/// position Dist. If so, return true and record information about the
/// preceding kills in NewKills.
bool TwoAddressInstructionPass::
canUpdateDeletedKills(SmallVector<unsigned, 4> &Kills,
SmallVector<NewKill, 4> &NewKills,
MachineBasicBlock *MBB, unsigned Dist) {
while (!Kills.empty()) {
unsigned Kill = Kills.back();
Kills.pop_back();
if (TargetRegisterInfo::isPhysicalRegister(Kill))
return false;
MachineInstr *LastKill = FindLastUseInMBB(Kill, MBB, Dist);
if (!LastKill)
return false;
bool isModRef = LastKill->definesRegister(Kill);
NewKills.push_back(std::make_pair(std::make_pair(Kill, isModRef),
LastKill));
}
return true;
}
/// DeleteUnusedInstr - If an instruction with a tied register operand can
/// be safely deleted, just delete it.
bool
TwoAddressInstructionPass::DeleteUnusedInstr(MachineBasicBlock::iterator &mi,
MachineBasicBlock::iterator &nmi,
MachineFunction::iterator &mbbi,
unsigned Dist) {
// Check if the instruction has no side effects and if all its defs are dead.
SmallVector<unsigned, 4> Kills;
if (!isSafeToDelete(mi, TII, Kills))
return false;
// If this instruction kills some virtual registers, we need to
// update the kill information. If it's not possible to do so,
// then bail out.
SmallVector<NewKill, 4> NewKills;
if (!canUpdateDeletedKills(Kills, NewKills, &*mbbi, Dist))
return false;
if (LV) {
while (!NewKills.empty()) {
MachineInstr *NewKill = NewKills.back().second;
unsigned Kill = NewKills.back().first.first;
bool isDead = NewKills.back().first.second;
NewKills.pop_back();
if (LV->removeVirtualRegisterKilled(Kill, mi)) {
if (isDead)
LV->addVirtualRegisterDead(Kill, NewKill);
else
LV->addVirtualRegisterKilled(Kill, NewKill);
}
}
}
mbbi->erase(mi); // Nuke the old inst.
mi = nmi;
return true;
}
/// RescheduleMIBelowKill - If there is one more local instruction that reads
/// 'Reg' and it kills 'Reg, consider moving the instruction below the kill
/// instruction in order to eliminate the need for the copy.
@ -1126,16 +1031,7 @@ TryInstructionTransform(MachineBasicBlock::iterator &mi,
assert(TargetRegisterInfo::isVirtualRegister(regB) &&
"cannot make instruction into two-address form");
// If regA is dead and the instruction can be deleted, just delete
// it so it doesn't clobber regB.
bool regBKilled = isKilled(MI, regB, MRI, TII);
if (!regBKilled && MI.getOperand(DstIdx).isDead() &&
DeleteUnusedInstr(mi, nmi, mbbi, Dist)) {
++NumDeletes;
DEBUG(dbgs() << "\tdeleted unused instruction.\n");
return true; // Done with this instruction."
}
if (TargetRegisterInfo::isVirtualRegister(regA))
ScanUses(regA, &*mbbi, Processed);