Protect against null dereferences

[akshaykhadse]

Fixed clang-format issues

[XinWang10]

llvm/lib/CodeGen/CodeGenPrepare.cpp

7071

This may be useless, we don't init TrueBranch only when TrueInstrs.size()==0.

7074

Ditto.

llvm/lib/TableGen/TGParser.cpp

585

I see ArgumentInit just have 2 kinds, so ArgName could always be inited.

llvm/lib/Target/X86/X86ISelLowering.cpp

5967

I find this is mostly called by combine*, I think the type could be legal here, so will not be 0 here? Otherwise we could crash.

llvm/lib/CodeGen/CodeGenPrepare.cpp

bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
 
   static const unsigned MD[] = {
       LLVMContext::MD_prof, LLVMContext::MD_unpredictable,
       LLVMContext::MD_make_implicit, LLVMContext::MD_dbg};
   StartBlock->getTerminator()->copyMetadata(*SI, MD);
 
   // Sink expensive instructions into the conditional blocks to avoid executing
   // them speculatively.
-  for (Instruction *I : TrueInstrs)
+  for (Instruction *I : TrueInstrs) {
+    assert(TrueBranch != nullptr && "TrueBranch must be initialized");
     I->moveBefore(TrueBranch);
-  for (Instruction *I : FalseInstrs)
+  }
+  for (Instruction *I : FalseInstrs) {
+    assert(FalseBranch != nullptr && "FalseBranch must be initialized");
     I->moveBefore(FalseBranch);
+  }
 
   // If we did not create a new block for one of the 'true' or 'false' paths
   // of the condition, it means that side of the branch goes to the end block
   // directly and the path originates from the start block from the point of
   // view of the new PHI.
   if (TrueBlock == nullptr)
     TrueBlock = StartBlock;
   else if (FalseBlock == nullptr)

llvm/lib/TableGen/TGParser.cpp

for (auto *Arg : ArgValues) {
     Init *ArgName = nullptr;
     Init *ArgValue = Arg->getValue();
     if (Arg->isPositional())
       ArgName = ArgNames[Arg->getIndex()];
     if (Arg->isNamed())
       ArgName = Arg->getName();
 
     // We can only specify the template argument once.
-    if (!is_contained(UnsolvedArgNames, ArgName))
+    if (!is_contained(UnsolvedArgNames, ArgName)){
+      assert(ArgName != nullptr && "ArgName must be initialized");
       return Error(Loc, "We can only specify the template argument '" +
                             ArgName->getAsUnquotedString() + "' once");
+    }
 
     ArgValueHandler(ArgName, ArgValue);
     llvm::erase_value(UnsolvedArgNames, ArgName);
   }
 
   // For unsolved arguments, if there is no default value, complain.
   for (auto *UnsolvedArgName : UnsolvedArgNames) {
     Init *Default = Rec->getValue(UnsolvedArgName)->getValue();

llvm/lib/Target/X86/X86ISelLowering.cpp

if (!SrcVT.isSimple() || (SrcVT.getSizeInBits() % 128) != 0 ||
       return false;
 
     // We can only handle all-signbits extensions.
     APInt DemandedSrcElts =
         DemandedElts.zextOrTrunc(SrcVT.getVectorNumElements());
     if (DAG.ComputeNumSignBits(Src, DemandedSrcElts) != NumBitsPerSrcElt)
       return false;
 
+    // Call DAG->ComputeNumSignBits(Src, DemandedSrcElts, 0U) may return 0
+    assert(NumBitsPerSrcElt != 0 && "Modulo by zero");
     assert((NumBitsPerElt % NumBitsPerSrcElt) == 0 && "Unexpected extension");
     unsigned Scale = NumBitsPerElt / NumBitsPerSrcElt;
     for (unsigned I = 0; I != NumElts; ++I)
       Mask.append(Scale, I);
     Ops.push_back(Src);
     return true;
   }
   case ISD::ZERO_EXTEND: