[CodeGen] Allow printing MachineMemOperands with less context in SDAGDumper

[thegameg]

Summary

Don't assume SelectionDAG is non-null as the targets can use it with a null pointer.

[thegameg]

Ping?

[bogner]

Would this be easier to follow if we overloaded printMemOperand with a variant that took the variables we're declaring here (M, MF, etc) and simply called into it? The "if (G)" condition would set them up and the "else" side would just pass null pointers.

In any case, LGTM. Feel free to commit once you've tried that and decided which is better.

[thegameg]

Thanks! Your suggestion is much more readable.

lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp

#else
     OS << (const void*)&Node;
 #endif
   });
 }
 
 // Print the MMO with more information from the SelectionDAG.
 static void printMemOperand(raw_ostream &OS, const MachineMemOperand &MMO,
                             const SelectionDAG *G) {
-  const MachineFunction &MF = G->getMachineFunction();
-  const Function &F = MF.getFunction();
-  const MachineFrameInfo &MFI = MF.getFrameInfo();
-  const TargetInstrInfo *TII = G->getSubtarget().getInstrInfo();
-  ModuleSlotTracker MST(F.getParent());
-  MST.incorporateFunction(F);
+  const Module *M = nullptr;
+  const MachineFunction *MF = nullptr;
+  const MachineFrameInfo *MFI = nullptr;
+  const TargetInstrInfo *TII = nullptr;
+  LLVMContext *Ctx = nullptr;
+  std::unique_ptr<LLVMContext> CtxPtr;
+  if (G) {
+    MF = &G->getMachineFunction();
+    M = MF->getFunction().getParent();
+    MFI = &MF->getFrameInfo();
+    TII = G->getSubtarget().getInstrInfo();
+    Ctx = G->getContext();
+  } else {
+    CtxPtr = llvm::make_unique<LLVMContext>();
+    Ctx = CtxPtr.get();
+  }
+  ModuleSlotTracker MST(M);
+  if (MF)
+    MST.incorporateFunction(MF->getFunction());
   SmallVector<StringRef, 0> SSNs;
-  MMO.print(OS, MST, SSNs, *G->getContext(), &MFI, TII);
+  MMO.print(OS, MST, SSNs, *Ctx, MFI, TII);
 }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void SDNode::dump() const { dump(nullptr); }
 
 LLVM_DUMP_METHOD void SDNode::dump(const SelectionDAG *G) const {
   print(dbgs(), G);
   dbgs() << '\n';