Index: lib/CodeGen/CriticalAntiDepBreaker.cpp
===================================================================
--- lib/CodeGen/CriticalAntiDepBreaker.cpp
+++ lib/CodeGen/CriticalAntiDepBreaker.cpp
@@ -444,6 +444,7 @@
 
 #ifndef NDEBUG
   {
+    assert(Max && "does not point to any node in the scheduling DAG");
     DEBUG(dbgs() << "Critical path has total latency "
           << (Max->getDepth() + Max->Latency) << "\n");
     DEBUG(dbgs() << "Available regs:");
@@ -458,6 +459,7 @@
   // Track progress along the critical path through the SUnit graph as we walk
   // the instructions.
   const SUnit *CriticalPathSU = Max;
+  assert(CriticalPathSU && "does not point to any node in the scheduling DAG");
   MachineInstr *CriticalPathMI = CriticalPathSU->getInstr();
 
   // Consider this pattern:
Index: lib/Target/NVPTX/NVPTXISelLowering.cpp
===================================================================
--- lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -1622,7 +1622,7 @@
 
         SmallVector<EVT, 4> LoadRetVTs;
         EVT TheLoadType = VTs[i];
-        if (retTy->isIntegerTy() && DL.getTypeAllocSizeInBits(retTy) < 32) {
+        if (retTy && retTy->isIntegerTy() && DL.getTypeAllocSizeInBits(retTy) < 32) {
           // This is for integer types only, and specifically not for
           // aggregates.
           LoadRetVTs.push_back(MVT::i32);
Index: lib/Target/PowerPC/PPCInstrInfo.cpp
===================================================================
--- lib/Target/PowerPC/PPCInstrInfo.cpp
+++ lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -525,6 +525,7 @@
   if (SecondLastInst && I != MBB.begin() && isUnpredicatedTerminator(*--I))
     return true;
 
+  assert(SecondLastInst && "does not point to a valid instruction");
   // If the block ends with PPC::B and PPC:BCC, handle it.
   if (SecondLastInst->getOpcode() == PPC::BCC &&
       LastInst->getOpcode() == PPC::B) {
Index: lib/Target/XCore/XCoreInstrInfo.cpp
===================================================================
--- lib/Target/XCore/XCoreInstrInfo.cpp
+++ lib/Target/XCore/XCoreInstrInfo.cpp
@@ -230,9 +230,9 @@
   MachineInstr *SecondLastInst = I;
 
   // If there are three terminators, we don't know what sort of block this is.
-  if (SecondLastInst && I != MBB.begin() && isUnpredicatedTerminator(*--I))
+  if (I != MBB.begin() && isUnpredicatedTerminator(*--I))
     return true;
-  
+
   unsigned SecondLastOpc    = SecondLastInst->getOpcode();
   XCore::CondCode BranchCode = GetCondFromBranchOpc(SecondLastOpc);
   
Index: lib/Transforms/ObjCARC/ObjCARCContract.cpp
===================================================================
--- lib/Transforms/ObjCARC/ObjCARCContract.cpp
+++ lib/Transforms/ObjCARC/ObjCARCContract.cpp
@@ -377,6 +377,7 @@
   Type *I8XX = PointerType::getUnqual(I8X);
 
   Value *Args[] = { Load->getPointerOperand(), New };
+  assert((Args[0] && Args[1]) && "is an empty Value array");
   if (Args[0]->getType() != I8XX)
     Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
   if (Args[1]->getType() != I8X)
Index: lib/Transforms/Scalar/LoadCombine.cpp
===================================================================
--- lib/Transforms/Scalar/LoadCombine.cpp
+++ lib/Transforms/Scalar/LoadCombine.cpp
@@ -188,10 +188,12 @@
   // Find first load. This is where we put the new load.
   LoadPOPPair FirstLP;
   FirstLP.InsertOrder = -1u;
+  FirstLP.POP.Pointer = nullptr;
   for (const auto &L : Loads)
     if (L.InsertOrder < FirstLP.InsertOrder)
       FirstLP = L;
 
+  assert(FirstLP.POP.Pointer && "could not find first load");
   unsigned AddressSpace =
       FirstLP.POP.Pointer->getType()->getPointerAddressSpace();
 
Index: lib/Transforms/Scalar/LoopStrengthReduce.cpp
===================================================================
--- lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2877,6 +2877,7 @@
     DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
     return;
   }
+  assert(IVSrc && "induction variable is needed to generate a chain");
 
   DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
   Type *IVTy = IVSrc->getType();