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Fix bug in kill flag updating for post-register-allocation scheduling. When the kill flag of a superreg needs to be cleared because there are one or more subregs live, we instead add implicit-defs of those subregs and leave the kill flag on the superreg. This allows us to end the live-range of the superreg without ending the live-ranges of the subregs. 

llvm-svn: 82629
This commit is contained in:
David Goodwin 2009-09-23 16:35:25 +00:00
parent b4bd0666d2
commit a4c98a3e34
1 changed files with 48 additions and 5 deletions
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51
llvm/lib/CodeGen/PostRASchedulerList.cpp
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@ -178,6 +178,11 @@ namespace {
unsigned LastNewReg,
const TargetRegisterClass *);
void StartBlockForKills(MachineBasicBlock *BB);
// ToggleKillFlag - Toggle a register operand kill flag. Other
// adjustments may be made to the instruction if necessary. Return
// true if the operand has been deleted, false if not.
bool ToggleKillFlag(MachineInstr *MI, MachineOperand &MO);
};
}
@ -822,6 +827,40 @@ void SchedulePostRATDList::StartBlockForKills(MachineBasicBlock *BB) {
}
}
bool SchedulePostRATDList::ToggleKillFlag(MachineInstr *MI,
MachineOperand &MO) {
// Setting kill flag...
if (!MO.isKill()) {
MO.setIsKill(true);
return false;
}
// If MO itself is live, clear the kill flag...
if (KillIndices[MO.getReg()] != ~0u) {
MO.setIsKill(false);
return false;
}
// If any subreg of MO is live, then create an imp-def for that
// subreg and keep MO marked as killed.
bool AllDead = true;
const unsigned SuperReg = MO.getReg();
for (const unsigned *Subreg = TRI->getSubRegisters(SuperReg);
*Subreg; ++Subreg) {
if (KillIndices[*Subreg] != ~0u) {
MI->addOperand(MachineOperand::CreateReg(*Subreg,
true /*IsDef*/,
true /*IsImp*/,
false /*IsKill*/,
false /*IsDead*/));
AllDead = false;
}
}
MO.setIsKill(AllDead);
return false;
}
/// FixupKills - Fix the register kill flags, they may have been made
/// incorrect by instruction reordering.
///
@ -860,9 +899,9 @@ void SchedulePostRATDList::FixupKills(MachineBasicBlock *MBB) {
}
}
// Examine all used registers and set kill flag. When a register
// is used multiple times we only set the kill flag on the first
// use.
// Examine all used registers and set/clear kill flag. When a
// register is used multiple times we only set the kill flag on
// the first use.
killedRegs.clear();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
@ -889,8 +928,12 @@ void SchedulePostRATDList::FixupKills(MachineBasicBlock *MBB) {
}
if (MO.isKill() != kill) {
MO.setIsKill(kill);
bool removed = ToggleKillFlag(MI, MO);
if (removed) {
DEBUG(errs() << "Fixed <removed> in ");
} else {
DEBUG(errs() << "Fixed " << MO << " in ");
}
DEBUG(MI->dump());
}