Hello LLVM Devs,
I have implemented delay slot filler pass for an architecture but I am getting problem in BasisBlock start label emission. Please provide some hints to solve this bug.
For indirect branch with dealy slots for following case :
addk r29,r3,r0
br r27
.LBB0_9:
it generates follwoing:
brd r27
addk r29,r3,r0
BB#9:
so after investigating it I found that it returns true from
bool AsmPrinter::
isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB)
because of no terminators in predecessor basic block
and so it does not print label in void AsmPrinter::EmitBasicBlockStart.
here is relevant code for my delay slot filler pass which is very similar to
Sparc PC’s delay slot filler pass.
bool Filler::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
bool Changed = false;
Subtarget = &MBB.getParent()->getSubtarget();
const TargetInstrInfo *TII = Subtarget->getInstrInfo();
for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ) {
MachineBasicBlock::iterator MI = I;
++I;
// If MI has no delay slot, skip.
if (!MI->hasDelaySlot())
continue;
MachineBasicBlock::iterator D = MBB.end();
if (!DisableDelaySlotFiller)
D = findDelayInstr(MBB, MI);
++FilledSlots;
Changed = true;
if (D == MBB.end()) {
BuildMI(MBB, I, MI->getDebugLoc(), TII->get(XXX::NOP));
} else {
MBB.splice(I, &MBB, D);
}
MIBundleBuilder(MBB, MI, --I);
}
return Changed;
}
MachineBasicBlock::iterator
Filler::findDelayInstr(MachineBasicBlock &MBB,
MachineBasicBlock::iterator slot)
{
SmallSet<unsigned, 32> RegDefs;
SmallSet<unsigned, 32> RegUses;
bool sawLoad = false;
bool sawStore = false;
if (slot == MBB.begin())
return MBB.end();
insertDefsUses(slot, RegDefs, RegUses);
bool done = false;
MachineBasicBlock::iterator I = slot;
while (!done) {
done = (I == MBB.begin());
if (!done)
–I;
// skip debug value
if (I->isDebugValue())
continue;
if (I->hasUnmodeledSideEffects() || I->hasDelaySlot() || isDelayFiller(MBB, I) || hasImmInstruction(I) || I->isBranch()
I->isCall() || I->isReturn() || I->isBarrier() || I->isInlineAsm())
break;
if (delayHasHazard(I, sawLoad, sawStore, RegDefs, RegUses)) {
insertDefsUses(I, RegDefs, RegUses);
continue;
}
return I;
}
return MBB.end();
}
Sincerely,
Vivek