Index: lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- lib/Bitcode/Writer/BitcodeWriter.cpp
+++ lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -2507,9 +2507,9 @@
 
   // For the module-level VST, add abbrev Ids for the VST_CODE_FNENTRY
   // records, which are not used in the per-function VSTs.
-  unsigned FnEntry8BitAbbrev;
-  unsigned FnEntry7BitAbbrev;
-  unsigned FnEntry6BitAbbrev;
+  unsigned FnEntry8BitAbbrev = VST_ENTRY_8_ABBREV;
+  unsigned FnEntry7BitAbbrev = VST_ENTRY_7_ABBREV;
+  unsigned FnEntry6BitAbbrev = VST_ENTRY_6_ABBREV;
   if (IsModuleLevel && hasVSTOffsetPlaceholder()) {
     // 8-bit fixed-width VST_CODE_FNENTRY function strings.
     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
Index: lib/CodeGen/ScheduleDAGInstrs.cpp
===================================================================
--- lib/CodeGen/ScheduleDAGInstrs.cpp
+++ lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -914,7 +914,8 @@
   for (MachineBasicBlock::iterator MII = RegionEnd, MIE = RegionBegin;
        MII != MIE; --MII) {
     MachineInstr *MI = std::prev(MII);
-    if (MI && DbgMI) {
+
+    if (DbgMI) {
       DbgValues.push_back(std::make_pair(DbgMI, MI));
       DbgMI = nullptr;
     }
Index: lib/Target/ARM/ARMFrameLowering.cpp
===================================================================
--- lib/Target/ARM/ARMFrameLowering.cpp
+++ lib/Target/ARM/ARMFrameLowering.cpp
@@ -1607,9 +1607,9 @@
   // FIXME: We could add logic to be more precise about negative offsets
   //        and which instructions will need a scratch register for them. Is it
   //        worth the effort and added fragility?
-  bool BigStack = (RS && (MFI->estimateStackSize(MF) +
-                              ((hasFP(MF) && AFI->hasStackFrame()) ? 4 : 0) >=
-                          estimateRSStackSizeLimit(MF, this))) ||
+  bool BigStack = ((MFI->estimateStackSize(MF) +
+                    ((hasFP(MF) && AFI->hasStackFrame()) ? 4 : 0) >=
+                    estimateRSStackSizeLimit(MF, this))) ||
                   MFI->hasVarSizedObjects() ||
                   (MFI->adjustsStack() && !canSimplifyCallFramePseudos(MF));
 
Index: lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
===================================================================
--- lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
+++ lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
@@ -406,6 +406,7 @@
     report_fatal_error("FIXME: relocations to absolute targets "
                        "not yet implemented");
   } else {
+    assert(A && "symbol is needed to resolve constant variables");
     // Resolve constant variables.
     if (A->isVariable()) {
       int64_t Res;
Index: lib/Target/ARM/Thumb2SizeReduction.cpp
===================================================================
--- lib/Target/ARM/Thumb2SizeReduction.cpp
+++ lib/Target/ARM/Thumb2SizeReduction.cpp
@@ -989,6 +989,7 @@
     }
 
     if (!NextInSameBundle && MI->isInsideBundle()) {
+      assert(BundleMI && "MachineInstr is null, abort reducing width of instructions");
       // FIXME: Since post-ra scheduler operates on bundles, the CPSR kill
       // marker is only on the BUNDLE instruction. Process the BUNDLE
       // instruction as we finish with the bundled instruction to work around
Index: lib/Target/Hexagon/HexagonCFGOptimizer.cpp
===================================================================
--- lib/Target/Hexagon/HexagonCFGOptimizer.cpp
+++ lib/Target/Hexagon/HexagonCFGOptimizer.cpp
@@ -180,6 +180,7 @@
           // Ensure that BB2 has one instruction -- an unconditional jump.
           if ((LayoutSucc->size() == 1) &&
               IsUnconditionalJump(LayoutSucc->front().getOpcode())) {
+            assert(JumpAroundTarget && "jump target is needed to process second basic block");
             MachineBasicBlock* UncondTarget =
               LayoutSucc->front().getOperand(0).getMBB();
             // Check if the layout successor of BB2 is BB3.
Index: lib/Target/Hexagon/RDFGraph.cpp
===================================================================
--- lib/Target/Hexagon/RDFGraph.cpp
+++ lib/Target/Hexagon/RDFGraph.cpp
@@ -1564,6 +1564,7 @@
   // Push block delimiters.
   markBlock(BA.Id, DefM);
 
+  assert(BA.Addr && "block node address is needed to create a data-flow link");
   // For each non-phi instruction in the block, link all the defs and uses
   // to their reaching defs. For any member of the block (including phis),
   // push the defs on the corresponding stacks.
Index: lib/Target/X86/AsmParser/X86AsmParser.cpp
===================================================================
--- lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -3002,6 +3002,7 @@
     getStreamer().InitSections(false);
     Section = getStreamer().getCurrentSection().first;
   }
+  assert(Section && "must have section to emit alignment");
   if (Section->UseCodeAlign())
     getStreamer().EmitCodeAlignment(2, 0);
   else
Index: lib/Transforms/Scalar/ScalarReplAggregates.cpp
===================================================================
--- lib/Transforms/Scalar/ScalarReplAggregates.cpp
+++ lib/Transforms/Scalar/ScalarReplAggregates.cpp
@@ -1986,6 +1986,7 @@
 /// and recursively continue updating all of its uses.
 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
                           SmallVectorImpl<AllocaInst *> &NewElts) {
+  assert((BC && AI) && "BitCast and Alloca cannot be null" );
   RewriteForScalarRepl(BC, AI, Offset, NewElts);
   if (BC->getOperand(0) != AI)
     return;
Index: lib/Transforms/Scalar/StructurizeCFG.cpp
===================================================================
--- lib/Transforms/Scalar/StructurizeCFG.cpp
+++ lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -719,6 +719,8 @@
 
 /// \brief Create a new or reuse the previous node as flow node
 BasicBlock *StructurizeCFG::needPrefix(bool NeedEmpty) {
+  assert(PrevNode && "cannot reuse null PrevNode as flow node");
+
   BasicBlock *Entry = PrevNode->getEntry();
 
   if (!PrevNode->isSubRegion()) {
Index: lib/Transforms/Scalar/TailRecursionElimination.cpp
===================================================================
--- lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -590,6 +590,7 @@
   if (CI->isTailCall() && CannotTailCallElimCallsMarkedTail)
     return nullptr;
 
+  assert(F && "BasicBlock parent did not have an enclosing method");
   // As a special case, detect code like this:
   //   double fabs(double f) { return __builtin_fabs(f); } // a 'fabs' call
   // and disable this xform in this case, because the code generator will