Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -1989,6 +1989,7 @@
 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
                                         LValue &LVal, QualType EltTy,
                                         int64_t Adjustment) {
+  assert(E && "expression to be evaluated must be not NULL");
   CharUnits SizeOfPointee;
   if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfPointee))
     return false;
Index: lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- lib/CodeGen/CGDebugInfo.cpp
+++ lib/CodeGen/CGDebugInfo.cpp
@@ -1312,6 +1312,7 @@
             CGM.getContext().toCharUnitsFromBits((int64_t)fieldOffset);
         V = CGM.getCXXABI().EmitMemberDataPointer(MPT, chars);
       }
+      assert(V && "constant must be not NULL at this point");
       TemplateParams.push_back(DBuilder.createTemplateValueParameter(
           TheCU, Name, TTy,
           cast_or_null<llvm::Constant>(V->stripPointerCasts())));
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -2303,6 +2303,7 @@
 
 unsigned CodeGenModule::GetGlobalVarAddressSpace(const VarDecl *D,
                                                  unsigned AddrSpace) {
+  assert(D && "variable declaration must be not NULL");
   if (LangOpts.CUDA && LangOpts.CUDAIsDevice) {
     if (D->hasAttr<CUDAConstantAttr>())
       AddrSpace = getContext().getTargetAddressSpace(LangAS::cuda_constant);
Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -434,6 +434,9 @@
 /// error, false otherwise.
 bool Sema::MergeCXXFunctionDecl(FunctionDecl *New, FunctionDecl *Old,
                                 Scope *S) {
+  assert(New && "New function declaration is NULL, aborting merge.");
+  assert(Old && "Old function declaration is NULL, aborting merge.");
+
   bool Invalid = false;
 
   // The declaration context corresponding to the scope is the semantic
Index: lib/Sema/SemaOpenMP.cpp
===================================================================
--- lib/Sema/SemaOpenMP.cpp
+++ lib/Sema/SemaOpenMP.cpp
@@ -939,6 +939,7 @@
         (VD && DSAStack->isForceVarCapturing()))
       return VD ? VD : Info.second;
     auto DVarPrivate = DSAStack->getTopDSA(D, DSAStack->isClauseParsingMode());
+    assert(DVarPrivate.PrivateCopy && "DSAStackTy object must be not NULL");
     if (DVarPrivate.CKind != OMPC_unknown && isOpenMPPrivate(DVarPrivate.CKind))
       return VD ? VD : cast<VarDecl>(DVarPrivate.PrivateCopy->getDecl());
     DVarPrivate = DSAStack->hasDSA(D, isOpenMPPrivate, MatchesAlways(),
@@ -3924,6 +3925,7 @@
 static ExprResult
 tryBuildCapture(Sema &SemaRef, Expr *Capture,
                 llvm::MapVector<Expr *, DeclRefExpr *> &Captures) {
+  assert(Capture && "cannot build capture if expression is NULL");
   if (Capture->isEvaluatable(SemaRef.Context, Expr::SE_AllowSideEffects))
     return SemaRef.PerformImplicitConversion(
         Capture->IgnoreImpCasts(), Capture->getType(), Sema::AA_Converting,
@@ -4177,7 +4179,7 @@
         SemaRef.Diag(CollapseLoopCountExpr->getExprLoc(),
                      diag::note_omp_collapse_ordered_expr)
             << 0 << CollapseLoopCountExpr->getSourceRange();
-      else
+      else if (OrderedLoopCountExpr)
         SemaRef.Diag(OrderedLoopCountExpr->getExprLoc(),
                      diag::note_omp_collapse_ordered_expr)
             << 1 << OrderedLoopCountExpr->getSourceRange();
Index: lib/Sema/SemaOverload.cpp
===================================================================
--- lib/Sema/SemaOverload.cpp
+++ lib/Sema/SemaOverload.cpp
@@ -8705,6 +8705,7 @@
 
 void Sema::diagnoseEquivalentInternalLinkageDeclarations(
     SourceLocation Loc, const NamedDecl *D, ArrayRef<const NamedDecl *> Equiv) {
+  assert(D && "named declaration must be not NULL");
   Diag(Loc, diag::ext_equivalent_internal_linkage_decl_in_modules) << D;
 
   Module *M = getOwningModule(const_cast<NamedDecl*>(D));
@@ -9185,7 +9186,9 @@
         !ToRefTy->getPointeeType()->isIncompleteType() &&
         S.IsDerivedFrom(SourceLocation(), ToRefTy->getPointeeType(), FromTy)) {
       BaseToDerivedConversion = 3;
-    } else if (ToTy->isLValueReferenceType() && !FromExpr->isLValue() &&
+    } else if (FromExpr &&
+               ToTy->isLValueReferenceType() &&
+               !FromExpr->isLValue() &&
                ToTy.getNonReferenceType().getCanonicalType() ==
                FromTy.getNonReferenceType().getCanonicalType()) {
       S.Diag(Fn->getLocation(), diag::note_ovl_candidate_bad_lvalue)
Index: lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
+++ lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
@@ -693,6 +693,8 @@
         !Param->getType()->isReferenceType())
       continue;
 
+    assert(ArgExpr && "cannot get the type of a NULL expression");
+
     NullConstraint Nullness = getNullConstraint(*ArgSVal, State);
 
     Nullability RequiredNullability =