ImplicitNullChecks: Don't add a dead definition of DepMI as live-in

[jonpa]

Summary

This is one of the fixes needed to reapply D68267 which improves verification of live-in lists.

[jonpa]

ping!

[craig.topper]

LGTM

[jonpa]

Thanks for revew - committed as f8c0cfc

llvm/lib/CodeGen/ImplicitNullChecks.cpp

for (const MachineOperand &MO : FaultingInstr->operands()) {
       Register Reg = MO.getReg();
       if (!Reg || MBB->isLiveIn(Reg))
         continue;
       MBB->addLiveIn(Reg);
     }
 
     if (auto *DepMI = NC.getOnlyDependency()) {
       for (auto &MO : DepMI->operands()) {
-        if (!MO.isReg() || !MO.getReg() || !MO.isDef())
+        if (!MO.isReg() || !MO.getReg() || !MO.isDef() || MO.isDead())
           continue;
         if (!NC.getNotNullSucc()->isLiveIn(MO.getReg()))
           NC.getNotNullSucc()->addLiveIn(MO.getReg());
       }
     }
 
     NC.getMemOperation()->eraseFromParent();
     NC.getCheckOperation()->eraseFromParent();

llvm/test/CodeGen/X86/implicit-null-checks.mir

 ---
 name:            inc_store_with_dep
 # CHECK-LABEL: inc_store_with_dep
 # CHECK: bb.0.entry:
 # CHECK:  $esi = ADD32rr killed $esi, killed $esi, implicit-def dead $eflags
 # CHECK-NEXT:  $noreg = FAULTING_OP 3, %bb.2, {{[0-9]+}}, $rdi, 1, $noreg, 16, $noreg, $esi
 # CHECK-NEXT: JMP_1 %bb.1
 # CHECK: bb.1.not_null
+# CHECK-NOT: liveins: {{.*}} $eflags
 
 alignment:       16
 tracksRegLiveness: true
 liveins:
   - { reg: '$rdi' }
   - { reg: '$rsi' }
 body:             |
   bb.0.entry: