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Add debug output to MipsDelaySlotFiller pass 

Summary:
I was tracking down a code-generation bug in this pass and found that the
added output was useful. It is also helpful to find out why a delay slot
could not be filled even though there is clearly a valid instruction (which
appears to mostly be caused by CFI instructions).

Reviewers: atanasyan

Reviewed By: atanasyan

Subscribers: merge_guards_bot, sdardis, hiraditya, jrtc27, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70940
This commit is contained in:
Alex Richardson 2019-12-04 10:05:02 +00:00
parent ba71e84430
commit 0cc4b95985
1 changed files with 28 additions and 5 deletions
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33
llvm/lib/Target/Mips/MipsDelaySlotFiller.cpp
View File

@ -612,12 +612,18 @@ bool MipsDelaySlotFiller::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
if (MipsCompactBranchPolicy.getValue() != CB_Always ||
!TII->getEquivalentCompactForm(I)) {
if (searchBackward(MBB, *I)) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": found instruction for delay slot"
" in backwards search.\n");
Filled = true;
} else if (I->isTerminator()) {
if (searchSuccBBs(MBB, I)) {
Filled = true;
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": found instruction for delay slot"
" in successor BB search.\n");
}
} else if (searchForward(MBB, I)) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": found instruction for delay slot"
" in forwards search.\n");
Filled = true;
}
}
@ -662,6 +668,8 @@ bool MipsDelaySlotFiller::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
}
// Bundle the NOP to the instruction with the delay slot.
LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": could not fill delay slot for ";
I->dump());
BuildMI(MBB, std::next(I), I->getDebugLoc(), TII->get(Mips::NOP));
MIBundleBuilder(MBB, I, std::next(I, 2));
++FilledSlots;
@ -679,13 +687,19 @@ bool MipsDelaySlotFiller::searchRange(MachineBasicBlock &MBB, IterTy Begin,
for (IterTy I = Begin; I != End;) {
IterTy CurrI = I;
++I;
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": checking instruction: "; CurrI->dump());
// skip debug value
if (CurrI->isDebugInstr())
if (CurrI->isDebugInstr()) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": ignoring debug instruction: ";
CurrI->dump());
continue;
}
if (terminateSearch(*CurrI))
if (terminateSearch(*CurrI)) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": should terminate search: ";
CurrI->dump());
break;
}
assert((!CurrI->isCall() && !CurrI->isReturn() && !CurrI->isBranch()) &&
"Cannot put calls, returns or branches in delay slot.");
@ -731,6 +745,9 @@ bool MipsDelaySlotFiller::searchRange(MachineBasicBlock &MBB, IterTy Begin,
continue;
Filler = CurrI;
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": found instruction for delay slot: ";
CurrI->dump());
return true;
}
@ -751,8 +768,11 @@ bool MipsDelaySlotFiller::searchBackward(MachineBasicBlock &MBB,
MachineBasicBlock::iterator SlotI = Slot;
if (!searchRange(MBB, ++SlotI.getReverse(), MBB.rend(), RegDU, MemDU, Slot,
Filler))
Filler)) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": could not find instruction for delay "
"slot using backwards search.\n");
return false;
}
MBB.splice(std::next(SlotI), &MBB, Filler.getReverse());
MIBundleBuilder(MBB, SlotI, std::next(SlotI, 2));
@ -772,8 +792,11 @@ bool MipsDelaySlotFiller::searchForward(MachineBasicBlock &MBB,
RegDU.setCallerSaved(*Slot);
if (!searchRange(MBB, std::next(Slot), MBB.end(), RegDU, NM, Slot, Filler))
if (!searchRange(MBB, std::next(Slot), MBB.end(), RegDU, NM, Slot, Filler)) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE ": could not find instruction for delay "
"slot using forwards search.\n");
return false;
}
MBB.splice(std::next(Slot), &MBB, Filler);
MIBundleBuilder(MBB, Slot, std::next(Slot, 2));