[StatepointLowering] Fix possible nullptr access in debug output

[danilaml]

Summary

SI.StatepointInstr would be nullptr if we came from LowerCallSiteWithDeoptBundleImpl.

[anna]

llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp

1160

Need this?

[danilaml]

llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp

1160

This is intentional, since the "fixed" debug print won't execute for this code path, so this helps trace optimization steps.

llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp

SDValue SelectionDAGBuilder::LowerAsSTATEPOINT(
 
   NumOfStatepoints++;
   // Clear state
   StatepointLowering.startNewStatepoint(*this);
   assert(SI.Bases.size() == SI.Ptrs.size() && "Pointer without base!");
   assert((GFI || SI.Bases.empty()) &&
          "No gc specified, so cannot relocate pointers!");
 
-  LLVM_DEBUG(dbgs() << "Lowering statepoint " << *SI.StatepointInstr << "\n");
+  LLVM_DEBUG(if (SI.StatepointInstr) dbgs()
+             << "Lowering statepoint " << *SI.StatepointInstr << "\n");
 #ifndef NDEBUG
   for (const auto *Reloc : SI.GCRelocates)
     if (Reloc->getParent() == SI.StatepointInstr->getParent())
       StatepointLowering.scheduleRelocCall(*Reloc);
 #endif
 
   // Lower statepoint vmstate and gcstate arguments
 
void SelectionDAGBuilder::LowerCallSiteWithDeoptBundleImpl(
 
   SI.DeoptState =
       ArrayRef<const Use>(DeoptBundle.Inputs.begin(), DeoptBundle.Inputs.end());
   SI.StatepointFlags = static_cast<uint64_t>(StatepointFlags::None);
   SI.EHPadBB = EHPadBB;
 
   // NB! The GC arguments are deliberately left empty.
 
+  LLVM_DEBUG(dbgs() << "Lowering call with deopt bundle " << *Call << "\n");
   if (SDValue ReturnVal = LowerAsSTATEPOINT(SI)) {
     ReturnVal = lowerRangeToAssertZExt(DAG, *Call, ReturnVal);
     setValue(Call, ReturnVal);
   }
 }
 
 void SelectionDAGBuilder::LowerCallSiteWithDeoptBundle(
     const CallBase *Call, SDValue Callee, const BasicBlock *EHPadBB) {