MachineVerifier: Don't crash if MachineOperand has no parent

[arsenm]

Summary

If you somehow added a MachineOperand to an instruction
that did not have the parent set, the verifier would
crash since it attempts to use the operand's parent.

[qcolombet]

Hi Matt,

Any chance you can add a test case?

Cheers,
-Quentin

[qcolombet]

Hmm, in that case, why do we need that check?

I just wonder how we could end up in such situation if we use the dedicated APIs.

[qcolombet]

I see :).
Looks like the RemoveOperand/addOperand gymnastic may bit someone else.

LGTM.

Q.

lib/CodeGen/MachineVerifier.cpp

336

Maybe add a comment saying that we should make sure to use RemoveOperand/addOperand or ChangeTo APIs.

[arsenm]

r236249

lib/CodeGen/MachineVerifier.cpp

for (MachineBasicBlock::const_instr_iterator MBBI = MFI->instr_begin(),
       if (!MBBI->isInsideBundle()) {
         if (CurBundle)
           visitMachineBundleAfter(CurBundle);
         CurBundle = MBBI;
         visitMachineBundleBefore(CurBundle);
       } else if (!CurBundle)
         report("No bundle header", MBBI);
       visitMachineInstrBefore(MBBI);
-      for (unsigned I = 0, E = MBBI->getNumOperands(); I != E; ++I)
-        visitMachineOperand(&MBBI->getOperand(I), I);
+      for (unsigned I = 0, E = MBBI->getNumOperands(); I != E; ++I) {
+        const MachineInstr &MI = *MBBI;
+        const MachineOperand &Op = MI.getOperand(I);
+          if (Op.getParent() != &MI)
+            report("Instruction has operand with wrong parent set", &MI);
+
+        visitMachineOperand(&Op, I);
+      }
+
       visitMachineInstrAfter(MBBI);
 
       // Was this the last bundled instruction?
       InBundle = MBBI->isBundledWithSucc();
     }
     if (CurBundle)
       visitMachineBundleAfter(CurBundle);
     if (InBundle)