Index: include/clang/AST/Expr.h
===================================================================
--- include/clang/AST/Expr.h
+++ include/clang/AST/Expr.h
@@ -1720,19 +1720,19 @@
 
 private:
   unsigned Opc : 5;
+  unsigned CanOverflow : 1;
   SourceLocation Loc;
   Stmt *Val;
 public:
-
-  UnaryOperator(Expr *input, Opcode opc, QualType type,
-                ExprValueKind VK, ExprObjectKind OK, SourceLocation l)
-    : Expr(UnaryOperatorClass, type, VK, OK,
-           input->isTypeDependent() || type->isDependentType(),
-           input->isValueDependent(),
-           (input->isInstantiationDependent() ||
-            type->isInstantiationDependentType()),
-           input->containsUnexpandedParameterPack()),
-      Opc(opc), Loc(l), Val(input) {}
+  UnaryOperator(Expr *input, Opcode opc, QualType type, ExprValueKind VK,
+                ExprObjectKind OK, SourceLocation l, bool CanOverflow)
+      : Expr(UnaryOperatorClass, type, VK, OK,
+             input->isTypeDependent() || type->isDependentType(),
+             input->isValueDependent(),
+             (input->isInstantiationDependent() ||
+              type->isInstantiationDependentType()),
+             input->containsUnexpandedParameterPack()),
+        Opc(opc), CanOverflow(CanOverflow), Loc(l), Val(input) {}
 
   /// \brief Build an empty unary operator.
   explicit UnaryOperator(EmptyShell Empty)
@@ -1748,6 +1748,15 @@
   SourceLocation getOperatorLoc() const { return Loc; }
   void setOperatorLoc(SourceLocation L) { Loc = L; }
 
+  /// Returns true if the unary operator can cause an overflow. For instance,
+  ///   signed int i = INT_MAX; i++;
+  ///   signed char c = CHAR_MAX; c++;
+  /// Due to integer promotions, c++ is promoted to an int before the postfix
+  /// increment, and the result is an int that cannot overflow. However, i++
+  /// can overflow.
+  bool canOverflow() const { return CanOverflow; }
+  void setCanOverflow(bool C) { CanOverflow = C; }
+
   /// isPostfix - Return true if this is a postfix operation, like x++.
   static bool isPostfix(Opcode Op) {
     return Op == UO_PostInc || Op == UO_PostDec;
Index: lib/AST/ASTDumper.cpp
===================================================================
--- lib/AST/ASTDumper.cpp
+++ lib/AST/ASTDumper.cpp
@@ -2217,6 +2217,8 @@
   VisitExpr(Node);
   OS << " " << (Node->isPostfix() ? "postfix" : "prefix")
      << " '" << UnaryOperator::getOpcodeStr(Node->getOpcode()) << "'";
+  if (!Node->canOverflow())
+    OS << " cannot overflow";
 }
 
 void ASTDumper::VisitUnaryExprOrTypeTraitExpr(
Index: lib/AST/ASTImporter.cpp
===================================================================
--- lib/AST/ASTImporter.cpp
+++ lib/AST/ASTImporter.cpp
@@ -5120,14 +5120,13 @@
   if (!SubExpr)
     return nullptr;
 
-  return new (Importer.getToContext()) UnaryOperator(SubExpr, E->getOpcode(),
-                                                     T, E->getValueKind(),
-                                                     E->getObjectKind(),
-                                         Importer.Import(E->getOperatorLoc()));                                        
+  return new (Importer.getToContext()) UnaryOperator(
+      SubExpr, E->getOpcode(), T, E->getValueKind(), E->getObjectKind(),
+      Importer.Import(E->getOperatorLoc()), E->canOverflow());
 }
 
-Expr *ASTNodeImporter::VisitUnaryExprOrTypeTraitExpr(
-                                            UnaryExprOrTypeTraitExpr *E) {
+Expr *
+ASTNodeImporter::VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E) {
   QualType ResultType = Importer.Import(E->getType());
   
   if (E->isArgumentType()) {
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -3247,11 +3247,6 @@
   return Obj && modifySubobject(Info, E, Obj, LVal.Designator, Val);
 }
 
-static bool isOverflowingIntegerType(ASTContext &Ctx, QualType T) {
-  return T->isSignedIntegerType() &&
-         Ctx.getIntWidth(T) >= Ctx.getIntWidth(Ctx.IntTy);
-}
-
 namespace {
 struct CompoundAssignSubobjectHandler {
   EvalInfo &Info;
@@ -3373,7 +3368,7 @@
 namespace {
 struct IncDecSubobjectHandler {
   EvalInfo &Info;
-  const Expr *E;
+  const UnaryOperator *E;
   AccessKinds AccessKind;
   APValue *Old;
 
@@ -3445,16 +3440,14 @@
     if (AccessKind == AK_Increment) {
       ++Value;
 
-      if (!WasNegative && Value.isNegative() &&
-          isOverflowingIntegerType(Info.Ctx, SubobjType)) {
+      if (!WasNegative && Value.isNegative() && E->canOverflow()) {
         APSInt ActualValue(Value, /*IsUnsigned*/true);
         return HandleOverflow(Info, E, ActualValue, SubobjType);
       }
     } else {
       --Value;
 
-      if (WasNegative && !Value.isNegative() &&
-          isOverflowingIntegerType(Info.Ctx, SubobjType)) {
+      if (WasNegative && !Value.isNegative() && E->canOverflow()) {
         unsigned BitWidth = Value.getBitWidth();
         APSInt ActualValue(Value.sext(BitWidth + 1), /*IsUnsigned*/false);
         ActualValue.setBit(BitWidth);
@@ -3515,7 +3508,7 @@
 
   AccessKinds AK = IsIncrement ? AK_Increment : AK_Decrement;
   CompleteObject Obj = findCompleteObject(Info, E, AK, LVal, LValType);
-  IncDecSubobjectHandler Handler = { Info, E, AK, Old };
+  IncDecSubobjectHandler Handler = {Info, cast<UnaryOperator>(E), AK, Old};
   return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
 }
 
@@ -8878,7 +8871,7 @@
       return false;
     if (!Result.isInt()) return Error(E);
     const APSInt &Value = Result.getInt();
-    if (Value.isSigned() && Value.isMinSignedValue() &&
+    if (Value.isSigned() && Value.isMinSignedValue() && E->canOverflow() &&
         !HandleOverflow(Info, E, -Value.extend(Value.getBitWidth() + 1),
                         E->getType()))
       return false;
Index: lib/Analysis/BodyFarm.cpp
===================================================================
--- lib/Analysis/BodyFarm.cpp
+++ lib/Analysis/BodyFarm.cpp
@@ -149,7 +149,8 @@
 
 UnaryOperator *ASTMaker::makeDereference(const Expr *Arg, QualType Ty) {
   return new (C) UnaryOperator(const_cast<Expr*>(Arg), UO_Deref, Ty,
-                               VK_LValue, OK_Ordinary, SourceLocation());
+                               VK_LValue, OK_Ordinary, SourceLocation(),
+                              /*CanOverflow*/ false);
 }
 
 ImplicitCastExpr *ASTMaker::makeLvalueToRvalue(const Expr *Arg, QualType Ty) {
@@ -441,7 +442,8 @@
       /* opc=*/ UO_LNot,
       /* QualType=*/ C.IntTy,
       /* ExprValueKind=*/ VK_RValue,
-      /* ExprObjectKind=*/ OK_Ordinary, SourceLocation());
+      /* ExprObjectKind=*/ OK_Ordinary, SourceLocation(),
+      /* CanOverflow*/ false);
 
   // Create assignment.
   BinaryOperator *FlagAssignment = M.makeAssignment(
@@ -505,7 +507,8 @@
   // (2) Create the assignment to the predicate.
   Expr *DoneValue =
       new (C) UnaryOperator(M.makeIntegerLiteral(0, C.LongTy), UO_Not, C.LongTy,
-                            VK_RValue, OK_Ordinary, SourceLocation());
+                            VK_RValue, OK_Ordinary, SourceLocation(),
+                            /*CanOverflow*/false);
 
   BinaryOperator *B =
     M.makeAssignment(
Index: lib/CodeGen/CGExprScalar.cpp
===================================================================
--- lib/CodeGen/CGExprScalar.cpp
+++ lib/CodeGen/CGExprScalar.cpp
@@ -165,7 +165,7 @@
 
   // If a unary op has a widened operand, the op cannot overflow.
   if (const auto *UO = dyn_cast<UnaryOperator>(Op.E))
-    return IsWidenedIntegerOp(Ctx, UO->getSubExpr());
+    return !UO->canOverflow();
 
   // We usually don't need overflow checks for binops with widened operands.
   // Multiplication with promoted unsigned operands is a special case.
@@ -1873,7 +1873,7 @@
       return Builder.CreateNSWAdd(InVal, Amount, Name);
     // Fall through.
   case LangOptions::SOB_Trapping:
-    if (IsWidenedIntegerOp(CGF.getContext(), E->getSubExpr()))
+    if (!E->canOverflow())
       return Builder.CreateNSWAdd(InVal, Amount, Name);
     return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, InVal, IsInc));
   }
@@ -1955,11 +1955,9 @@
   } else if (type->isIntegerType()) {
     // Note that signed integer inc/dec with width less than int can't
     // overflow because of promotion rules; we're just eliding a few steps here.
-    bool CanOverflow = value->getType()->getIntegerBitWidth() >=
-                       CGF.IntTy->getIntegerBitWidth();
-    if (CanOverflow && type->isSignedIntegerOrEnumerationType()) {
+    if (E->canOverflow() && type->isSignedIntegerOrEnumerationType()) {
       value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);
-    } else if (CanOverflow && type->isUnsignedIntegerType() &&
+    } else if (E->canOverflow() && type->isUnsignedIntegerType() &&
                CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) {
       value =
           EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, value, isInc));
Index: lib/CodeGen/CGObjC.cpp
===================================================================
--- lib/CodeGen/CGObjC.cpp
+++ lib/CodeGen/CGObjC.cpp
@@ -3268,12 +3268,12 @@
   DeclRefExpr DstExpr(&DstDecl, false, DestTy,
                       VK_RValue, SourceLocation());
   UnaryOperator DST(&DstExpr, UO_Deref, DestTy->getPointeeType(),
-                    VK_LValue, OK_Ordinary, SourceLocation());
+                    VK_LValue, OK_Ordinary, SourceLocation(), false);
   
   DeclRefExpr SrcExpr(&SrcDecl, false, SrcTy,
                       VK_RValue, SourceLocation());
   UnaryOperator SRC(&SrcExpr, UO_Deref, SrcTy->getPointeeType(),
-                    VK_LValue, OK_Ordinary, SourceLocation());
+                    VK_LValue, OK_Ordinary, SourceLocation(), false);
   
   Expr *Args[2] = { &DST, &SRC };
   CallExpr *CalleeExp = cast<CallExpr>(PID->getSetterCXXAssignment());
@@ -3351,7 +3351,7 @@
                       VK_RValue, SourceLocation());
   
   UnaryOperator SRC(&SrcExpr, UO_Deref, SrcTy->getPointeeType(),
-                    VK_LValue, OK_Ordinary, SourceLocation());
+                    VK_LValue, OK_Ordinary, SourceLocation(), false);
   
   CXXConstructExpr *CXXConstExpr = 
     cast<CXXConstructExpr>(PID->getGetterCXXConstructor());
Index: lib/CodeGen/CGStmtOpenMP.cpp
===================================================================
--- lib/CodeGen/CGStmtOpenMP.cpp
+++ lib/CodeGen/CGStmtOpenMP.cpp
@@ -2483,7 +2483,7 @@
                         OK_Ordinary, S.getLocStart(), FPOptions());
     // Increment for loop counter.
     UnaryOperator Inc(&IVRefExpr, UO_PreInc, KmpInt32Ty, VK_RValue, OK_Ordinary,
-                      S.getLocStart());
+                      S.getLocStart(), true);
     auto BodyGen = [Stmt, CS, &S, &IV](CodeGenFunction &CGF) {
       // Iterate through all sections and emit a switch construct:
       // switch (IV) {
Index: lib/Frontend/Rewrite/RewriteModernObjC.cpp
===================================================================
--- lib/Frontend/Rewrite/RewriteModernObjC.cpp
+++ lib/Frontend/Rewrite/RewriteModernObjC.cpp
@@ -2590,7 +2590,7 @@
   Expr *Unop = new (Context) UnaryOperator(DRE, UO_AddrOf,
                                  Context->getPointerType(DRE->getType()),
                                            VK_RValue, OK_Ordinary,
-                                           SourceLocation());
+                                           SourceLocation(), false);
   // cast to NSConstantString *
   CastExpr *cast = NoTypeInfoCStyleCastExpr(Context, Exp->getType(),
                                             CK_CPointerToObjCPointerCast, Unop);
@@ -3295,7 +3295,7 @@
       SuperRep = new (Context) UnaryOperator(SuperRep, UO_AddrOf,
                                Context->getPointerType(SuperRep->getType()),
                                              VK_RValue, OK_Ordinary,
-                                             SourceLocation());
+                                             SourceLocation(), false);
       SuperRep = NoTypeInfoCStyleCastExpr(Context,
                                           Context->getPointerType(superType),
                                           CK_BitCast, SuperRep);
@@ -3313,7 +3313,7 @@
       SuperRep = new (Context) UnaryOperator(SuperRep, UO_AddrOf,
                                Context->getPointerType(SuperRep->getType()),
                                              VK_RValue, OK_Ordinary,
-                                             SourceLocation());
+                                             SourceLocation(), false);
     }
     MsgExprs.push_back(SuperRep);
     break;
@@ -3389,7 +3389,7 @@
       SuperRep = new (Context) UnaryOperator(SuperRep, UO_AddrOf,
                                Context->getPointerType(SuperRep->getType()),
                                VK_RValue, OK_Ordinary,
-                               SourceLocation());
+                               SourceLocation(), false);
       SuperRep = NoTypeInfoCStyleCastExpr(Context,
                                Context->getPointerType(superType),
                                CK_BitCast, SuperRep);
@@ -4720,7 +4720,7 @@
       return DRE;
   Expr *Exp = new (Context) UnaryOperator(DRE, UO_Deref, DRE->getType(),
                                           VK_LValue, OK_Ordinary,
-                                          DRE->getLocation());
+                                          DRE->getLocation(), false);
   // Need parens to enforce precedence.
   ParenExpr *PE = new (Context) ParenExpr(SourceLocation(), SourceLocation(), 
                                           Exp);
@@ -5314,7 +5314,7 @@
                                 UO_AddrOf,
                                 Context->getPointerType(Context->VoidPtrTy), 
                                 VK_RValue, OK_Ordinary,
-                                SourceLocation());
+                                SourceLocation(), false);
   InitExprs.push_back(DescRefExpr); 
   
   // Add initializers for any closure decl refs.
@@ -5332,7 +5332,8 @@
           QualType QT = (*I)->getType();
           QT = Context->getPointerType(QT);
           Exp = new (Context) UnaryOperator(Exp, UO_AddrOf, QT, VK_RValue,
-                                            OK_Ordinary, SourceLocation());
+                                            OK_Ordinary, SourceLocation(),
+                                            false);
         }
       } else if (isTopLevelBlockPointerType((*I)->getType())) {
         FD = SynthBlockInitFunctionDecl((*I)->getName());
@@ -5348,7 +5349,8 @@
           QualType QT = (*I)->getType();
           QT = Context->getPointerType(QT);
           Exp = new (Context) UnaryOperator(Exp, UO_AddrOf, QT, VK_RValue,
-                                            OK_Ordinary, SourceLocation());
+                                            OK_Ordinary, SourceLocation(),
+                                            false);
         }
         
       }
@@ -5388,7 +5390,8 @@
       if (!isNestedCapturedVar)
           Exp = new (Context) UnaryOperator(Exp, UO_AddrOf,
                                      Context->getPointerType(Exp->getType()),
-                                     VK_RValue, OK_Ordinary, SourceLocation());
+                                     VK_RValue, OK_Ordinary, SourceLocation(),
+                                     false);
       Exp = NoTypeInfoCStyleCastExpr(Context, castT, CK_BitCast, Exp);
       InitExprs.push_back(Exp);
     }
@@ -5414,7 +5417,7 @@
   
   NewRep = new (Context) UnaryOperator(NewRep, UO_AddrOf,
                              Context->getPointerType(NewRep->getType()),
-                             VK_RValue, OK_Ordinary, SourceLocation());
+                             VK_RValue, OK_Ordinary, SourceLocation(), false);
   NewRep = NoTypeInfoCStyleCastExpr(Context, FType, CK_BitCast,
                                     NewRep);
   // Put Paren around the call.
@@ -7558,7 +7561,7 @@
       
       Expr *Exp = new (Context) UnaryOperator(castExpr, UO_Deref, IvarT,
                                               VK_LValue, OK_Ordinary,
-                                              SourceLocation());
+                                              SourceLocation(), false);
       PE = new (Context) ParenExpr(OldRange.getBegin(),
                                    OldRange.getEnd(),
                                    Exp);
Index: lib/Frontend/Rewrite/RewriteObjC.cpp
===================================================================
--- lib/Frontend/Rewrite/RewriteObjC.cpp
+++ lib/Frontend/Rewrite/RewriteObjC.cpp
@@ -2511,7 +2511,7 @@
   Expr *Unop = new (Context) UnaryOperator(DRE, UO_AddrOf,
                                  Context->getPointerType(DRE->getType()),
                                            VK_RValue, OK_Ordinary,
-                                           SourceLocation());
+                                           SourceLocation(), false);
   // cast to NSConstantString *
   CastExpr *cast = NoTypeInfoCStyleCastExpr(Context, Exp->getType(),
                                             CK_CPointerToObjCPointerCast, Unop);
@@ -2712,7 +2712,7 @@
       SuperRep = new (Context) UnaryOperator(SuperRep, UO_AddrOf,
                                Context->getPointerType(SuperRep->getType()),
                                              VK_RValue, OK_Ordinary,
-                                             SourceLocation());
+                                             SourceLocation(), false);
       SuperRep = NoTypeInfoCStyleCastExpr(Context,
                                           Context->getPointerType(superType),
                                           CK_BitCast, SuperRep);
@@ -2730,7 +2730,7 @@
       SuperRep = new (Context) UnaryOperator(SuperRep, UO_AddrOf,
                                Context->getPointerType(SuperRep->getType()),
                                              VK_RValue, OK_Ordinary,
-                                             SourceLocation());
+                                             SourceLocation(), false);
     }
     MsgExprs.push_back(SuperRep);
     break;
@@ -2806,7 +2806,7 @@
       SuperRep = new (Context) UnaryOperator(SuperRep, UO_AddrOf,
                                Context->getPointerType(SuperRep->getType()),
                                VK_RValue, OK_Ordinary,
-                               SourceLocation());
+                               SourceLocation(), false);
       SuperRep = NoTypeInfoCStyleCastExpr(Context,
                                Context->getPointerType(superType),
                                CK_BitCast, SuperRep);
@@ -3045,7 +3045,7 @@
                                                VK_LValue, SourceLocation());
   Expr *DerefExpr = new (Context) UnaryOperator(DRE, UO_AddrOf,
                              Context->getPointerType(DRE->getType()),
-                             VK_RValue, OK_Ordinary, SourceLocation());
+                             VK_RValue, OK_Ordinary, SourceLocation(), false);
   CastExpr *castExpr = NoTypeInfoCStyleCastExpr(Context, DerefExpr->getType(),
                                                 CK_BitCast,
                                                 DerefExpr);
@@ -3875,7 +3875,7 @@
       return DRE;
   Expr *Exp = new (Context) UnaryOperator(DRE, UO_Deref, DRE->getType(),
                                           VK_LValue, OK_Ordinary,
-                                          DRE->getLocation());
+                                          DRE->getLocation(), false);
   // Need parens to enforce precedence.
   ParenExpr *PE = new (Context) ParenExpr(SourceLocation(), SourceLocation(), 
                                           Exp);
@@ -4438,7 +4438,7 @@
                                 UO_AddrOf,
                                 Context->getPointerType(Context->VoidPtrTy), 
                                 VK_RValue, OK_Ordinary,
-                                SourceLocation());
+                                SourceLocation(), false);
   InitExprs.push_back(DescRefExpr); 
   
   // Add initializers for any closure decl refs.
@@ -4456,7 +4456,8 @@
           QualType QT = (*I)->getType();
           QT = Context->getPointerType(QT);
           Exp = new (Context) UnaryOperator(Exp, UO_AddrOf, QT, VK_RValue,
-                                            OK_Ordinary, SourceLocation());
+                                            OK_Ordinary, SourceLocation(),
+                                            false);
         }
       } else if (isTopLevelBlockPointerType((*I)->getType())) {
         FD = SynthBlockInitFunctionDecl((*I)->getName());
@@ -4472,7 +4473,8 @@
           QualType QT = (*I)->getType();
           QT = Context->getPointerType(QT);
           Exp = new (Context) UnaryOperator(Exp, UO_AddrOf, QT, VK_RValue,
-                                            OK_Ordinary, SourceLocation());
+                                            OK_Ordinary, SourceLocation(),
+                                            false);
         }
       }
       InitExprs.push_back(Exp);
@@ -4509,9 +4511,9 @@
       // captured nested byref variable has its address passed. Do not take
       // its address again.
       if (!isNestedCapturedVar)
-          Exp = new (Context) UnaryOperator(Exp, UO_AddrOf,
-                                     Context->getPointerType(Exp->getType()),
-                                     VK_RValue, OK_Ordinary, SourceLocation());
+        Exp = new (Context) UnaryOperator(
+            Exp, UO_AddrOf, Context->getPointerType(Exp->getType()), VK_RValue,
+            OK_Ordinary, SourceLocation(), false);
       Exp = NoTypeInfoCStyleCastExpr(Context, castT, CK_BitCast, Exp);
       InitExprs.push_back(Exp);
     }
@@ -4529,7 +4531,7 @@
                                   FType, VK_LValue, SourceLocation());
   NewRep = new (Context) UnaryOperator(NewRep, UO_AddrOf,
                              Context->getPointerType(NewRep->getType()),
-                             VK_RValue, OK_Ordinary, SourceLocation());
+                             VK_RValue, OK_Ordinary, SourceLocation(), false);
   NewRep = NoTypeInfoCStyleCastExpr(Context, FType, CK_BitCast,
                                     NewRep);
   BlockDeclRefs.clear();
Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -10990,11 +10990,11 @@
   Expr *From = FromB.build(S, Loc);
   From = new (S.Context) UnaryOperator(From, UO_AddrOf,
                          S.Context.getPointerType(From->getType()),
-                         VK_RValue, OK_Ordinary, Loc);
+                         VK_RValue, OK_Ordinary, Loc, false);
   Expr *To = ToB.build(S, Loc);
   To = new (S.Context) UnaryOperator(To, UO_AddrOf,
                        S.Context.getPointerType(To->getType()),
-                       VK_RValue, OK_Ordinary, Loc);
+                       VK_RValue, OK_Ordinary, Loc, false);
 
   const Type *E = T->getBaseElementTypeUnsafe();
   bool NeedsCollectableMemCpy =
@@ -11233,10 +11233,12 @@
                                      BO_NE, S.Context.BoolTy,
                                      VK_RValue, OK_Ordinary, Loc, FPOptions());
 
-  // Create the pre-increment of the iteration variable.
-  Expr *Increment
-    = new (S.Context) UnaryOperator(IterationVarRef.build(S, Loc), UO_PreInc,
-                                    SizeType, VK_LValue, OK_Ordinary, Loc);
+  // Create the pre-increment of the iteration variable. We can determine
+  // whether the increment will overflow based on the value of the array
+  // bound.
+  Expr *Increment = new (S.Context)
+      UnaryOperator(IterationVarRef.build(S, Loc), UO_PreInc, SizeType,
+                    VK_LValue, OK_Ordinary, Loc, Upper.isMaxValue());
 
   // Construct the loop that copies all elements of this array.
   return S.ActOnForStmt(
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -12161,6 +12161,16 @@
   return CreateBuiltinBinOp(OpLoc, Opc, LHSExpr, RHSExpr);
 }
 
+static bool isOverflowingIntegerType(ASTContext &Ctx, QualType T) {
+  if (T.isNull() || T->isDependentType())
+    return false;
+
+  if (!T->isPromotableIntegerType())
+    return true;
+
+  return Ctx.getIntWidth(T) >= Ctx.getIntWidth(Ctx.IntTy);
+}
+
 ExprResult Sema::CreateBuiltinUnaryOp(SourceLocation OpLoc,
                                       UnaryOperatorKind Opc,
                                       Expr *InputExpr) {
@@ -12168,6 +12178,8 @@
   ExprValueKind VK = VK_RValue;
   ExprObjectKind OK = OK_Ordinary;
   QualType resultType;
+  bool CanOverflow = false;
+
   bool ConvertHalfVec = false;
   if (getLangOpts().OpenCL) {
     QualType Ty = InputExpr->getType();
@@ -12193,6 +12205,7 @@
                                                 Opc == UO_PostInc,
                                                 Opc == UO_PreInc ||
                                                 Opc == UO_PreDec);
+    CanOverflow = isOverflowingIntegerType(Context, resultType);
     break;
   case UO_AddrOf:
     resultType = CheckAddressOfOperand(Input, OpLoc);
@@ -12206,6 +12219,8 @@
   }
   case UO_Plus:
   case UO_Minus:
+    CanOverflow = Opc == UO_Minus &&
+                  isOverflowingIntegerType(Context, Input.get()->getType());
     Input = UsualUnaryConversions(Input.get());
     if (Input.isInvalid()) return ExprError();
     // Unary plus and minus require promoting an operand of half vector to a
@@ -12242,6 +12257,7 @@
     if (Input.isInvalid())
       return ExprError();
     resultType = Input.get()->getType();
+
     if (resultType->isDependentType())
       break;
     // C99 6.5.3.3p1. We allow complex int and float as a GCC extension.
@@ -12356,7 +12372,7 @@
     CheckArrayAccess(Input.get());
 
   auto *UO = new (Context)
-      UnaryOperator(Input.get(), Opc, resultType, VK, OK, OpLoc);
+      UnaryOperator(Input.get(), Opc, resultType, VK, OK, OpLoc, CanOverflow);
   // Convert the result back to a half vector.
   if (ConvertHalfVec)
     return convertVector(UO, Context.HalfTy, *this);
Index: lib/Sema/SemaExprObjC.cpp
===================================================================
--- lib/Sema/SemaExprObjC.cpp
+++ lib/Sema/SemaExprObjC.cpp
@@ -4276,9 +4276,9 @@
   } else if (UnaryOperator *uo = dyn_cast<UnaryOperator>(e)) {
     assert(uo->getOpcode() == UO_Extension);
     Expr *sub = stripARCUnbridgedCast(uo->getSubExpr());
-    return new (Context) UnaryOperator(sub, UO_Extension, sub->getType(),
-                                   sub->getValueKind(), sub->getObjectKind(),
-                                       uo->getOperatorLoc());
+    return new (Context)
+        UnaryOperator(sub, UO_Extension, sub->getType(), sub->getValueKind(),
+                      sub->getObjectKind(), uo->getOperatorLoc(), false);
   } else if (GenericSelectionExpr *gse = dyn_cast<GenericSelectionExpr>(e)) {
     assert(!gse->isResultDependent());
 
Index: lib/Sema/SemaOverload.cpp
===================================================================
--- lib/Sema/SemaOverload.cpp
+++ lib/Sema/SemaOverload.cpp
@@ -11992,7 +11992,7 @@
   if (Input->isTypeDependent()) {
     if (Fns.empty())
       return new (Context) UnaryOperator(Input, Opc, Context.DependentTy,
-                                         VK_RValue, OK_Ordinary, OpLoc);
+                                         VK_RValue, OK_Ordinary, OpLoc, false);
 
     CXXRecordDecl *NamingClass = nullptr; // lookup ignores member operators
     UnresolvedLookupExpr *Fn
@@ -13522,7 +13522,7 @@
 
         return new (Context) UnaryOperator(SubExpr, UO_AddrOf, MemPtrType,
                                            VK_RValue, OK_Ordinary,
-                                           UnOp->getOperatorLoc());
+                                           UnOp->getOperatorLoc(), false);
       }
     }
     Expr *SubExpr = FixOverloadedFunctionReference(UnOp->getSubExpr(),
@@ -13533,7 +13533,7 @@
     return new (Context) UnaryOperator(SubExpr, UO_AddrOf,
                                      Context.getPointerType(SubExpr->getType()),
                                        VK_RValue, OK_Ordinary,
-                                       UnOp->getOperatorLoc());
+                                       UnOp->getOperatorLoc(), false);
   }
 
   // C++ [except.spec]p17:
Index: lib/Sema/SemaPseudoObject.cpp
===================================================================
--- lib/Sema/SemaPseudoObject.cpp
+++ lib/Sema/SemaPseudoObject.cpp
@@ -132,7 +132,8 @@
                                              uop->getType(),
                                              uop->getValueKind(),
                                              uop->getObjectKind(),
-                                             uop->getOperatorLoc());
+                                             uop->getOperatorLoc(),
+                                             uop->canOverflow());
       }
 
       if (GenericSelectionExpr *gse = dyn_cast<GenericSelectionExpr>(e)) {
@@ -527,9 +528,12 @@
       (result.get()->isTypeDependent() || CanCaptureValue(result.get())))
     setResultToLastSemantic();
 
-  UnaryOperator *syntactic =
-    new (S.Context) UnaryOperator(syntacticOp, opcode, resultType,
-                                  VK_LValue, OK_Ordinary, opcLoc);
+  UnaryOperator *syntactic = new (S.Context) UnaryOperator(
+      syntacticOp, opcode, resultType, VK_LValue, OK_Ordinary, opcLoc,
+      !resultType->isDependentType()
+          ? S.Context.getTypeSize(resultType) >=
+                S.Context.getTypeSize(S.Context.IntTy)
+          : false);
   return complete(syntactic);
 }
 
@@ -1550,7 +1554,7 @@
   // Do nothing if the operand is dependent.
   if (op->isTypeDependent())
     return new (Context) UnaryOperator(op, opcode, Context.DependentTy,
-                                       VK_RValue, OK_Ordinary, opcLoc);
+                                       VK_RValue, OK_Ordinary, opcLoc, false);
 
   assert(UnaryOperator::isIncrementDecrementOp(opcode));
   Expr *opaqueRef = op->IgnoreParens();
@@ -1633,9 +1637,9 @@
   Expr *syntax = E->getSyntacticForm();
   if (UnaryOperator *uop = dyn_cast<UnaryOperator>(syntax)) {
     Expr *op = stripOpaqueValuesFromPseudoObjectRef(*this, uop->getSubExpr());
-    return new (Context) UnaryOperator(op, uop->getOpcode(), uop->getType(),
-                                       uop->getValueKind(), uop->getObjectKind(),
-                                       uop->getOperatorLoc());
+    return new (Context) UnaryOperator(
+        op, uop->getOpcode(), uop->getType(), uop->getValueKind(),
+        uop->getObjectKind(), uop->getOperatorLoc(), uop->canOverflow());
   } else if (CompoundAssignOperator *cop
                = dyn_cast<CompoundAssignOperator>(syntax)) {
     Expr *lhs = stripOpaqueValuesFromPseudoObjectRef(*this, cop->getLHS());
Index: lib/Serialization/ASTReaderStmt.cpp
===================================================================
--- lib/Serialization/ASTReaderStmt.cpp
+++ lib/Serialization/ASTReaderStmt.cpp
@@ -553,6 +553,7 @@
   E->setSubExpr(Record.readSubExpr());
   E->setOpcode((UnaryOperator::Opcode)Record.readInt());
   E->setOperatorLoc(ReadSourceLocation());
+  E->setCanOverflow(Record.readInt());
 }
 
 void ASTStmtReader::VisitOffsetOfExpr(OffsetOfExpr *E) {
Index: lib/Serialization/ASTWriterStmt.cpp
===================================================================
--- lib/Serialization/ASTWriterStmt.cpp
+++ lib/Serialization/ASTWriterStmt.cpp
@@ -509,6 +509,7 @@
   Record.AddStmt(E->getSubExpr());
   Record.push_back(E->getOpcode()); // FIXME: stable encoding
   Record.AddSourceLocation(E->getOperatorLoc());
+  Record.push_back(E->canOverflow());
   Code = serialization::EXPR_UNARY_OPERATOR;
 }
 
Index: test/Misc/ast-dump-stmt.c
===================================================================
--- test/Misc/ast-dump-stmt.c
+++ test/Misc/ast-dump-stmt.c
@@ -33,3 +33,35 @@
 // CHECK-NEXT:   OpaqueValueExpr
 // CHECK-NEXT:     IntegerLiteral
 // CHECK-NEXT:   IntegerLiteral
+
+void TestUnaryOperatorExpr(void) {
+  char T1 = 1;
+  int T2 = 1;
+
+  T1++;
+  T2++;
+  // CHECK:      UnaryOperator{{.*}}postfix '++' cannot overflow
+  // CHECK-NEXT:   DeclRefExpr{{.*}}'T1' 'char'
+  // CHECK-NOT:  UnaryOperator{{.*}}postfix '++' cannot overflow
+  // CHECK:        DeclRefExpr{{.*}}'T2' 'int'
+
+  -T1;
+  -T2;
+  // CHECK:      UnaryOperator{{.*}}prefix '-' cannot overflow
+  // CHECK-NEXT:   ImplicitCastExpr
+  // CHECK-NEXT:     ImplicitCastExpr
+  // CHECK-NEXT:       DeclRefExpr{{.*}}'T1' 'char'
+  // CHECK-NOT:  UnaryOperator{{.*}}prefix '-' cannot overflow
+  // CHECK:        ImplicitCastExpr
+  // CHECK:          DeclRefExpr{{.*}}'T2' 'int'
+
+  ~T1;
+  ~T2;
+  // CHECK:      UnaryOperator{{.*}}prefix '~' cannot overflow
+  // CHECK-NEXT:   ImplicitCastExpr
+  // CHECK-NEXT:     ImplicitCastExpr
+  // CHECK-NEXT:       DeclRefExpr{{.*}}'T1' 'char'
+  // CHECK:  	 UnaryOperator{{.*}}prefix '~' cannot overflow
+  // CHECK-NEXT:     ImplicitCastExpr
+  // CHECK-NEXT:       DeclRefExpr{{.*}}'T2' 'int'
+}