diff --git a/clang/include/clang/AST/Expr.h b/clang/include/clang/AST/Expr.h
--- a/clang/include/clang/AST/Expr.h
+++ b/clang/include/clang/AST/Expr.h
@@ -500,14 +500,13 @@
   /// semantically correspond to a bool.
   bool isKnownToHaveBooleanValue(bool Semantic = true) const;
 
-  /// isIntegerConstantExpr - Return true if this expression is a valid integer
-  /// constant expression, and, if so, return its value in Result.  If not a
-  /// valid i-c-e, return false and fill in Loc (if specified) with the location
-  /// of the invalid expression.
+  /// isIntegerConstantExpr - Return the value if this expression is a valid integer
+  /// constant expression.  If not a valid i-c-e, return None and fill in Loc
+  /// (if specified) with the location of the invalid expression.
   ///
   /// Note: This does not perform the implicit conversions required by C++11
   /// [expr.const]p5.
-  bool isIntegerConstantExpr(llvm::APSInt &Result, const ASTContext &Ctx,
+  Optional<llvm::APSInt> getIntegerConstantExpr(const ASTContext &Ctx,
                              SourceLocation *Loc = nullptr,
                              bool isEvaluated = true) const;
   bool isIntegerConstantExpr(const ASTContext &Ctx,
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -9212,17 +9212,15 @@
           const ConstantArrayType* CAT)
           -> std::pair<bool,llvm::APInt> {
         if (VAT) {
-          llvm::APSInt TheInt;
+          Optional<llvm::APSInt> TheInt;
           Expr *E = VAT->getSizeExpr();
-          if (E && E->isIntegerConstantExpr(TheInt, *this))
-            return std::make_pair(true, TheInt);
-          else
-            return std::make_pair(false, TheInt);
-        } else if (CAT) {
-            return std::make_pair(true, CAT->getSize());
-        } else {
-            return std::make_pair(false, llvm::APInt());
+          if (E && (TheInt = E->getIntegerConstantExpr(*this)))
+            return std::make_pair(true, *TheInt);
+          return std::make_pair(false, llvm::APSInt());
         }
+        if (CAT)
+          return std::make_pair(true, CAT->getSize());
+        return std::make_pair(false, llvm::APInt());
       };
 
       bool HaveLSize, HaveRSize;
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -14580,16 +14580,22 @@
   return true;
 }
 
-bool Expr::isIntegerConstantExpr(llvm::APSInt &Value, const ASTContext &Ctx,
-                                 SourceLocation *Loc, bool isEvaluated) const {
+Optional<llvm::APSInt> Expr::getIntegerConstantExpr(const ASTContext &Ctx,
+                                                    SourceLocation *Loc,
+                                                    bool isEvaluated) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
-  if (Ctx.getLangOpts().CPlusPlus11)
-    return EvaluateCPlusPlus11IntegralConstantExpr(Ctx, this, &Value, Loc);
+  APSInt Value;
+
+  if (Ctx.getLangOpts().CPlusPlus11) {
+    if (EvaluateCPlusPlus11IntegralConstantExpr(Ctx, this, &Value, Loc))
+      return Value;
+    return None;
+  }
 
   if (!isIntegerConstantExpr(Ctx, Loc))
-    return false;
+    return None;
 
   // The only possible side-effects here are due to UB discovered in the
   // evaluation (for instance, INT_MAX + 1). In such a case, we are still
@@ -14603,8 +14609,7 @@
   if (!::EvaluateAsInt(this, ExprResult, Ctx, SE_AllowSideEffects, Info))
     llvm_unreachable("ICE cannot be evaluated!");
 
-  Value = ExprResult.Val.getInt();
-  return true;
+  return ExprResult.Val.getInt();
 }
 
 bool Expr::isCXX98IntegralConstantExpr(const ASTContext &Ctx) const {
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -1358,9 +1358,9 @@
 
 void MicrosoftCXXNameMangler::mangleExpression(const Expr *E) {
   // See if this is a constant expression.
-  llvm::APSInt Value;
-  if (E->isIntegerConstantExpr(Value, Context.getASTContext())) {
-    mangleIntegerLiteral(Value, E->getType()->isBooleanType());
+  if (Optional<llvm::APSInt> Value =
+          E->getIntegerConstantExpr(Context.getASTContext())) {
+    mangleIntegerLiteral(*Value, E->getType()->isBooleanType());
     return;
   }
 
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -4306,11 +4306,9 @@
       } else {
         // If this is required to be a constant, constant fold it so that we
         // know that the generated intrinsic gets a ConstantInt.
-        llvm::APSInt Result;
-        bool IsConst = E->getArg(i)->isIntegerConstantExpr(Result,getContext());
-        assert(IsConst && "Constant arg isn't actually constant?");
-        (void)IsConst;
-        ArgValue = llvm::ConstantInt::get(getLLVMContext(), Result);
+        ArgValue = llvm::ConstantInt::get(
+            getLLVMContext(),
+            *E->getArg(i)->getIntegerConstantExpr(getContext()));
       }
 
       // If the intrinsic arg type is different from the builtin arg type
@@ -5447,13 +5445,13 @@
     SmallVectorImpl<llvm::Value *> &Ops, Address PtrOp0, Address PtrOp1,
     llvm::Triple::ArchType Arch) {
   // Get the last argument, which specifies the vector type.
-  llvm::APSInt NeonTypeConst;
   const Expr *Arg = E->getArg(E->getNumArgs() - 1);
-  if (!Arg->isIntegerConstantExpr(NeonTypeConst, getContext()))
+  Optional<llvm::APSInt> NeonTypeConst = Arg->getIntegerConstantExpr(getContext());
+  if (!NeonTypeConst)
     return nullptr;
 
   // Determine the type of this overloaded NEON intrinsic.
-  NeonTypeFlags Type(NeonTypeConst.getZExtValue());
+  NeonTypeFlags Type(NeonTypeConst->getZExtValue());
   bool Usgn = Type.isUnsigned();
   bool Quad = Type.isQuad();
   const bool HasLegalHalfType = getTarget().hasLegalHalfType();
@@ -6672,10 +6670,9 @@
     } else {
       // If this is required to be a constant, constant fold it so that we know
       // that the generated intrinsic gets a ConstantInt.
-      llvm::APSInt Result;
-      bool IsConst = E->getArg(i)->isIntegerConstantExpr(Result, getContext());
-      assert(IsConst && "Constant arg isn't actually constant?"); (void)IsConst;
-      Ops.push_back(llvm::ConstantInt::get(getLLVMContext(), Result));
+      Ops.push_back(llvm::ConstantInt::get(
+          getLLVMContext(),
+          *E->getArg(i)->getIntegerConstantExpr(getContext())));
     }
   }
 
@@ -6875,9 +6872,9 @@
 
   // Get the last argument, which specifies the vector type.
   assert(HasExtraArg);
-  llvm::APSInt Result;
   const Expr *Arg = E->getArg(E->getNumArgs()-1);
-  if (!Arg->isIntegerConstantExpr(Result, getContext()))
+  Optional<llvm::APSInt> Result = Arg->getIntegerConstantExpr(getContext());
+  if (!Result)
     return nullptr;
 
   if (BuiltinID == ARM::BI__builtin_arm_vcvtr_f ||
@@ -6890,7 +6887,7 @@
       Ty = DoubleTy;
 
     // Determine whether this is an unsigned conversion or not.
-    bool usgn = Result.getZExtValue() == 1;
+    bool usgn = Result->getZExtValue() == 1;
     unsigned Int = usgn ? Intrinsic::arm_vcvtru : Intrinsic::arm_vcvtr;
 
     // Call the appropriate intrinsic.
@@ -6899,7 +6896,7 @@
   }
 
   // Determine the type of this overloaded NEON intrinsic.
-  NeonTypeFlags Type(Result.getZExtValue());
+  NeonTypeFlags Type = Result->getZExtValue();
   bool usgn = Type.isUnsigned();
   bool rightShift = false;
 
@@ -7042,11 +7039,7 @@
 
 template<typename Integer>
 static Integer GetIntegerConstantValue(const Expr *E, ASTContext &Context) {
-  llvm::APSInt IntVal;
-  bool IsConst = E->isIntegerConstantExpr(IntVal, Context);
-  assert(IsConst && "Sema should have checked this was a constant");
-  (void)IsConst;
-  return IntVal.getExtValue();
+  return E->getIntegerConstantExpr(Context)->getExtValue();
 }
 
 static llvm::Value *SignOrZeroExtend(CGBuilderTy &Builder, llvm::Value *V,
@@ -7316,13 +7309,13 @@
   assert(E->getNumArgs() >= 3);
 
   // Get the last argument, which specifies the vector type.
-  llvm::APSInt Result;
   const Expr *Arg = E->getArg(E->getNumArgs() - 1);
-  if (!Arg->isIntegerConstantExpr(Result, CGF.getContext()))
+  Optional<llvm::APSInt> Result = Arg->getIntegerConstantExpr(CGF.getContext());
+  if (!Result)
     return nullptr;
 
   // Determine the type of this overloaded NEON intrinsic.
-  NeonTypeFlags Type(Result.getZExtValue());
+  NeonTypeFlags Type = Result->getZExtValue();
   llvm::VectorType *Ty = GetNeonType(&CGF, Type);
   if (!Ty)
     return nullptr;
@@ -7940,11 +7933,9 @@
     } else {
       // If this is required to be a constant, constant fold it so that we know
       // that the generated intrinsic gets a ConstantInt.
-      llvm::APSInt Result;
-      bool IsConst = E->getArg(i)->isIntegerConstantExpr(Result, getContext());
-      assert(IsConst && "Constant arg isn't actually constant?");
-      (void)IsConst;
-      Ops.push_back(llvm::ConstantInt::get(getLLVMContext(), Result));
+      Ops.push_back(llvm::ConstantInt::get(
+          getLLVMContext(),
+          *E->getArg(i)->getIntegerConstantExpr(getContext())));
     }
   }
 
@@ -7959,12 +7950,11 @@
     return Result;
   }
 
-  llvm::APSInt Result;
   const Expr *Arg = E->getArg(E->getNumArgs()-1);
   NeonTypeFlags Type(0);
-  if (Arg->isIntegerConstantExpr(Result, getContext()))
+  if (Optional<llvm::APSInt> Result = Arg->getIntegerConstantExpr(getContext()))
     // Determine the type of this overloaded NEON intrinsic.
-    Type = NeonTypeFlags(Result.getZExtValue());
+    Type = NeonTypeFlags(Result->getZExtValue());
 
   bool usgn = Type.isUnsigned();
   bool quad = Type.isQuad();
@@ -10688,10 +10678,8 @@
 
     // If this is required to be a constant, constant fold it so that we know
     // that the generated intrinsic gets a ConstantInt.
-    llvm::APSInt Result;
-    bool IsConst = E->getArg(i)->isIntegerConstantExpr(Result, getContext());
-    assert(IsConst && "Constant arg isn't actually constant?"); (void)IsConst;
-    Ops.push_back(llvm::ConstantInt::get(getLLVMContext(), Result));
+    Ops.push_back(llvm::ConstantInt::get(
+        getLLVMContext(), *E->getArg(i)->getIntegerConstantExpr(getContext())));
   }
 
   // These exist so that the builtin that takes an immediate can be bounds
@@ -13798,11 +13786,8 @@
     llvm::Type *ResultType = ConvertType(E->getType());
     Value *X = EmitScalarExpr(E->getArg(0));
     // Constant-fold the M4 and M5 mask arguments.
-    llvm::APSInt M4, M5;
-    bool IsConstM4 = E->getArg(1)->isIntegerConstantExpr(M4, getContext());
-    bool IsConstM5 = E->getArg(2)->isIntegerConstantExpr(M5, getContext());
-    assert(IsConstM4 && IsConstM5 && "Constant arg isn't actually constant?");
-    (void)IsConstM4; (void)IsConstM5;
+    llvm::APSInt M4 = *E->getArg(1)->getIntegerConstantExpr(getContext());
+    llvm::APSInt M5 = *E->getArg(2)->getIntegerConstantExpr(getContext());
     // Check whether this instance can be represented via a LLVM standard
     // intrinsic.  We only support some combinations of M4 and M5.
     Intrinsic::ID ID = Intrinsic::not_intrinsic;
@@ -13857,10 +13842,7 @@
     Value *X = EmitScalarExpr(E->getArg(0));
     Value *Y = EmitScalarExpr(E->getArg(1));
     // Constant-fold the M4 mask argument.
-    llvm::APSInt M4;
-    bool IsConstM4 = E->getArg(2)->isIntegerConstantExpr(M4, getContext());
-    assert(IsConstM4 && "Constant arg isn't actually constant?");
-    (void)IsConstM4;
+    llvm::APSInt M4 = *E->getArg(2)->getIntegerConstantExpr(getContext());
     // Check whether this instance can be represented via a LLVM standard
     // intrinsic.  We only support some values of M4.
     Intrinsic::ID ID = Intrinsic::not_intrinsic;
@@ -13894,10 +13876,7 @@
     Value *X = EmitScalarExpr(E->getArg(0));
     Value *Y = EmitScalarExpr(E->getArg(1));
     // Constant-fold the M4 mask argument.
-    llvm::APSInt M4;
-    bool IsConstM4 = E->getArg(2)->isIntegerConstantExpr(M4, getContext());
-    assert(IsConstM4 && "Constant arg isn't actually constant?");
-    (void)IsConstM4;
+    llvm::APSInt M4 = *E->getArg(2)->getIntegerConstantExpr(getContext());
     // Check whether this instance can be represented via a LLVM standard
     // intrinsic.  We only support some values of M4.
     Intrinsic::ID ID = Intrinsic::not_intrinsic;
@@ -14564,10 +14543,11 @@
     Address Dst = EmitPointerWithAlignment(E->getArg(0));
     Value *Src = EmitScalarExpr(E->getArg(1));
     Value *Ldm = EmitScalarExpr(E->getArg(2));
-    llvm::APSInt isColMajorArg;
-    if (!E->getArg(3)->isIntegerConstantExpr(isColMajorArg, getContext()))
+    Optional<llvm::APSInt> isColMajorArg =
+        E->getArg(3)->getIntegerConstantExpr(getContext());
+    if (!isColMajorArg)
       return nullptr;
-    bool isColMajor = isColMajorArg.getSExtValue();
+    bool isColMajor = isColMajorArg->getSExtValue();
     NVPTXMmaLdstInfo II = getNVPTXMmaLdstInfo(BuiltinID);
     unsigned IID = isColMajor ? II.IID_col : II.IID_row;
     if (IID == 0)
@@ -14608,10 +14588,11 @@
     Value *Dst = EmitScalarExpr(E->getArg(0));
     Address Src = EmitPointerWithAlignment(E->getArg(1));
     Value *Ldm = EmitScalarExpr(E->getArg(2));
-    llvm::APSInt isColMajorArg;
-    if (!E->getArg(3)->isIntegerConstantExpr(isColMajorArg, getContext()))
+    Optional<llvm::APSInt> isColMajorArg =
+        E->getArg(3)->getIntegerConstantExpr(getContext());
+    if (!isColMajorArg)
       return nullptr;
-    bool isColMajor = isColMajorArg.getSExtValue();
+    bool isColMajor = isColMajorArg->getSExtValue();
     NVPTXMmaLdstInfo II = getNVPTXMmaLdstInfo(BuiltinID);
     unsigned IID = isColMajor ? II.IID_col : II.IID_row;
     if (IID == 0)
@@ -14658,16 +14639,20 @@
     Address SrcA = EmitPointerWithAlignment(E->getArg(1));
     Address SrcB = EmitPointerWithAlignment(E->getArg(2));
     Address SrcC = EmitPointerWithAlignment(E->getArg(3));
-    llvm::APSInt LayoutArg;
-    if (!E->getArg(4)->isIntegerConstantExpr(LayoutArg, getContext()))
+    Optional<llvm::APSInt> LayoutArg =
+        E->getArg(4)->getIntegerConstantExpr(getContext());
+    if (!LayoutArg)
       return nullptr;
-    int Layout = LayoutArg.getSExtValue();
+    int Layout = LayoutArg->getSExtValue();
     if (Layout < 0 || Layout > 3)
       return nullptr;
     llvm::APSInt SatfArg;
     if (BuiltinID == NVPTX::BI__bmma_m8n8k128_mma_xor_popc_b1)
       SatfArg = 0;  // .b1 does not have satf argument.
-    else if (!E->getArg(5)->isIntegerConstantExpr(SatfArg, getContext()))
+    else if (Optional<llvm::APSInt> OptSatfArg =
+                 E->getArg(5)->getIntegerConstantExpr(getContext()))
+      SatfArg = *OptSatfArg;
+    else
       return nullptr;
     bool Satf = SatfArg.getSExtValue();
     NVPTXMmaInfo MI = getNVPTXMmaInfo(BuiltinID);
@@ -14828,12 +14813,8 @@
     return Builder.CreateCall(Callee, Args);
   }
   case WebAssembly::BI__builtin_wasm_memory_init: {
-    llvm::APSInt SegConst;
-    if (!E->getArg(0)->isIntegerConstantExpr(SegConst, getContext()))
-      llvm_unreachable("Constant arg isn't actually constant?");
-    llvm::APSInt MemConst;
-    if (!E->getArg(1)->isIntegerConstantExpr(MemConst, getContext()))
-      llvm_unreachable("Constant arg isn't actually constant?");
+    llvm::APSInt SegConst = *E->getArg(0)->getIntegerConstantExpr(getContext());
+    llvm::APSInt MemConst = *E->getArg(1)->getIntegerConstantExpr(getContext());
     if (!MemConst.isNullValue())
       ErrorUnsupported(E, "non-zero memory index");
     Value *Args[] = {llvm::ConstantInt::get(getLLVMContext(), SegConst),
@@ -14844,9 +14825,7 @@
     return Builder.CreateCall(Callee, Args);
   }
   case WebAssembly::BI__builtin_wasm_data_drop: {
-    llvm::APSInt SegConst;
-    if (!E->getArg(0)->isIntegerConstantExpr(SegConst, getContext()))
-      llvm_unreachable("Constant arg isn't actually constant?");
+    llvm::APSInt SegConst = *E->getArg(0)->getIntegerConstantExpr(getContext());
     Value *Arg = llvm::ConstantInt::get(getLLVMContext(), SegConst);
     Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_data_drop);
     return Builder.CreateCall(Callee, {Arg});
@@ -14973,9 +14952,7 @@
   case WebAssembly::BI__builtin_wasm_extract_lane_i64x2:
   case WebAssembly::BI__builtin_wasm_extract_lane_f32x4:
   case WebAssembly::BI__builtin_wasm_extract_lane_f64x2: {
-    llvm::APSInt LaneConst;
-    if (!E->getArg(1)->isIntegerConstantExpr(LaneConst, getContext()))
-      llvm_unreachable("Constant arg isn't actually constant?");
+    llvm::APSInt LaneConst = *E->getArg(1)->getIntegerConstantExpr(getContext());
     Value *Vec = EmitScalarExpr(E->getArg(0));
     Value *Lane = llvm::ConstantInt::get(getLLVMContext(), LaneConst);
     Value *Extract = Builder.CreateExtractElement(Vec, Lane);
@@ -15001,9 +14978,7 @@
   case WebAssembly::BI__builtin_wasm_replace_lane_i64x2:
   case WebAssembly::BI__builtin_wasm_replace_lane_f32x4:
   case WebAssembly::BI__builtin_wasm_replace_lane_f64x2: {
-    llvm::APSInt LaneConst;
-    if (!E->getArg(1)->isIntegerConstantExpr(LaneConst, getContext()))
-      llvm_unreachable("Constant arg isn't actually constant?");
+    llvm::APSInt LaneConst = *E->getArg(1)->getIntegerConstantExpr(getContext());
     Value *Vec = EmitScalarExpr(E->getArg(0));
     Value *Lane = llvm::ConstantInt::get(getLLVMContext(), LaneConst);
     Value *Val = EmitScalarExpr(E->getArg(2));
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3760,15 +3760,17 @@
     llvm::APSInt ConstLength;
     if (Length) {
       // Idx = LowerBound + Length - 1;
-      if (Length->isIntegerConstantExpr(ConstLength, C)) {
-        ConstLength = ConstLength.zextOrTrunc(PointerWidthInBits);
+      if (Optional<llvm::APSInt> CL = Length->getIntegerConstantExpr(C)) {
+        ConstLength = CL->zextOrTrunc(PointerWidthInBits);
         Length = nullptr;
       }
       auto *LowerBound = E->getLowerBound();
       llvm::APSInt ConstLowerBound(PointerWidthInBits, /*isUnsigned=*/false);
-      if (LowerBound && LowerBound->isIntegerConstantExpr(ConstLowerBound, C)) {
-        ConstLowerBound = ConstLowerBound.zextOrTrunc(PointerWidthInBits);
-        LowerBound = nullptr;
+      if (LowerBound) {
+        if (Optional<llvm::APSInt> LB = LowerBound->getIntegerConstantExpr(C)) {
+          ConstLowerBound = LB->zextOrTrunc(PointerWidthInBits);
+          LowerBound = nullptr;
+        }
       }
       if (!Length)
         --ConstLength;
@@ -3805,8 +3807,10 @@
                              : BaseTy;
       if (auto *VAT = C.getAsVariableArrayType(ArrayTy)) {
         Length = VAT->getSizeExpr();
-        if (Length->isIntegerConstantExpr(ConstLength, C))
+        if (Optional<llvm::APSInt> L = Length->getIntegerConstantExpr(C)) {
+          ConstLength = *L;
           Length = nullptr;
+        }
       } else {
         auto *CAT = C.getAsConstantArrayType(ArrayTy);
         ConstLength = CAT->getSize();
diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -293,20 +293,20 @@
   // If specified then alignment must be a "small" power of two.
   unsigned AlignmentVal = 0;
   if (Alignment) {
-    llvm::APSInt Val;
+    Optional<llvm::APSInt> Val;
 
     // pack(0) is like pack(), which just works out since that is what
     // we use 0 for in PackAttr.
     if (Alignment->isTypeDependent() ||
         Alignment->isValueDependent() ||
-        !Alignment->isIntegerConstantExpr(Val, Context) ||
-        !(Val == 0 || Val.isPowerOf2()) ||
-        Val.getZExtValue() > 16) {
+        !(Val = Alignment->getIntegerConstantExpr(Context)) ||
+        !(*Val == 0 || Val->isPowerOf2()) ||
+        Val->getZExtValue() > 16) {
       Diag(PragmaLoc, diag::warn_pragma_pack_invalid_alignment);
       return; // Ignore
     }
 
-    AlignmentVal = (unsigned) Val.getZExtValue();
+    AlignmentVal = (unsigned) Val->getZExtValue();
   }
   if (Action == Sema::PSK_Show) {
     // Show the current alignment, making sure to show the right value
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -2097,10 +2097,7 @@
   if (CoprocArg->isTypeDependent() || CoprocArg->isValueDependent())
     return false;
 
-  llvm::APSInt CoprocNoAP;
-  bool IsICE = CoprocArg->isIntegerConstantExpr(CoprocNoAP, Context);
-  (void)IsICE;
-  assert(IsICE && "Coprocossor immediate is not a constant expression");
+  llvm::APSInt CoprocNoAP = *CoprocArg->getIntegerConstantExpr(Context);
   int64_t CoprocNo = CoprocNoAP.getExtValue();
   assert(CoprocNo >= 0 && "Coprocessor immediate must be non-negative");
 
@@ -2389,8 +2386,7 @@
   }
 
   // The second argument needs to be a constant int
-  llvm::APSInt Value;
-  if (!TheCall->getArg(1)->isIntegerConstantExpr(Value, Context)) {
+  if (!TheCall->getArg(1)->isIntegerConstantExpr(Context)) {
     Diag(Arg->getBeginLoc(), diag::err_preserve_field_info_not_const)
         << 2 << Arg->getSourceRange();
     return true;
@@ -2925,11 +2921,10 @@
                                            CallExpr *TheCall) {
   if (BuiltinID == SystemZ::BI__builtin_tabort) {
     Expr *Arg = TheCall->getArg(0);
-    llvm::APSInt AbortCode(32);
-    if (Arg->isIntegerConstantExpr(AbortCode, Context) &&
-        AbortCode.getSExtValue() >= 0 && AbortCode.getSExtValue() < 256)
-      return Diag(Arg->getBeginLoc(), diag::err_systemz_invalid_tabort_code)
-             << Arg->getSourceRange();
+    if (Optional<llvm::APSInt> AbortCode = Arg->getIntegerConstantExpr(Context))
+      if (AbortCode->getSExtValue() >= 0 && AbortCode->getSExtValue() < 256)
+        return Diag(Arg->getBeginLoc(), diag::err_systemz_invalid_tabort_code)
+               << Arg->getSourceRange();
   }
 
   // For intrinsics which take an immediate value as part of the instruction,
@@ -4586,21 +4581,19 @@
   }
 
   if (SubExprs.size() >= 2 && Form != Init) {
-    llvm::APSInt Result(32);
-    if (SubExprs[1]->isIntegerConstantExpr(Result, Context) &&
-        !isValidOrderingForOp(Result.getSExtValue(), Op))
-      Diag(SubExprs[1]->getBeginLoc(),
-           diag::warn_atomic_op_has_invalid_memory_order)
-          << SubExprs[1]->getSourceRange();
+    if (Optional<llvm::APSInt> Result = SubExprs[1]->getIntegerConstantExpr(Context))
+      if (!isValidOrderingForOp(Result->getSExtValue(), Op))
+        Diag(SubExprs[1]->getBeginLoc(),
+             diag::warn_atomic_op_has_invalid_memory_order)
+            << SubExprs[1]->getSourceRange();
   }
 
   if (auto ScopeModel = AtomicExpr::getScopeModel(Op)) {
     auto *Scope = Args[Args.size() - 1];
-    llvm::APSInt Result(32);
-    if (Scope->isIntegerConstantExpr(Result, Context) &&
-        !ScopeModel->isValid(Result.getZExtValue())) {
-      Diag(Scope->getBeginLoc(), diag::err_atomic_op_has_invalid_synch_scope)
-          << Scope->getSourceRange();
+    if (Optional<llvm::APSInt> Result = Scope->getIntegerConstantExpr(Context)) {
+      if (!ScopeModel->isValid(Result->getZExtValue()))
+        Diag(Scope->getBeginLoc(), diag::err_atomic_op_has_invalid_synch_scope)
+            << Scope->getSourceRange();
     }
     SubExprs.push_back(Scope);
   }
@@ -5468,8 +5461,7 @@
            << TheCall->getSourceRange();
 
   // Check the third argument is a compile time constant
-  llvm::APSInt Value;
-  if(!TheCall->getArg(2)->isIntegerConstantExpr(Value, Context))
+  if(!TheCall->getArg(2)->isIntegerConstantExpr(Context))
     return Diag(TheCall->getBeginLoc(),
                 diag::err_vsx_builtin_nonconstant_argument)
            << 3 /* argument index */ << TheCall->getDirectCallee()
@@ -5564,17 +5556,17 @@
         TheCall->getArg(i)->isValueDependent())
       continue;
 
-    llvm::APSInt Result(32);
-    if (!TheCall->getArg(i)->isIntegerConstantExpr(Result, Context))
+    Optional<llvm::APSInt> Result;
+    if (!(Result = TheCall->getArg(i)->getIntegerConstantExpr(Context)))
       return ExprError(Diag(TheCall->getBeginLoc(),
                             diag::err_shufflevector_nonconstant_argument)
                        << TheCall->getArg(i)->getSourceRange());
 
     // Allow -1 which will be translated to undef in the IR.
-    if (Result.isSigned() && Result.isAllOnesValue())
+    if (Result->isSigned() && Result->isAllOnesValue())
       continue;
 
-    if (Result.getActiveBits() > 64 || Result.getZExtValue() >= numElements*2)
+    if (Result->getActiveBits() > 64 || Result->getZExtValue() >= numElements*2)
       return ExprError(Diag(TheCall->getBeginLoc(),
                             diag::err_shufflevector_argument_too_large)
                        << TheCall->getArg(i)->getSourceRange());
@@ -5821,10 +5813,11 @@
 
   if (Arg->isTypeDependent() || Arg->isValueDependent()) return false;
 
-  if (!Arg->isIntegerConstantExpr(Result, Context))
+  Optional<llvm::APSInt> R;
+  if (!(R = Arg->getIntegerConstantExpr(Context)))
     return Diag(TheCall->getBeginLoc(), diag::err_constant_integer_arg_type)
            << FDecl->getDeclName() << Arg->getSourceRange();
-
+  Result = *R;
   return false;
 }
 
@@ -9978,14 +9971,15 @@
 
       // If the shift amount is a positive constant, drop the width by
       // that much.
-      llvm::APSInt shift;
-      if (BO->getRHS()->isIntegerConstantExpr(shift, C) &&
-          shift.isNonNegative()) {
-        unsigned zext = shift.getZExtValue();
-        if (zext >= L.Width)
-          L.Width = (L.NonNegative ? 0 : 1);
-        else
-          L.Width -= zext;
+      if (Optional<llvm::APSInt> shift =
+              BO->getRHS()->getIntegerConstantExpr(C)) {
+        if (shift->isNonNegative()) {
+          unsigned zext = shift->getZExtValue();
+          if (zext >= L.Width)
+            L.Width = (L.NonNegative ? 0 : 1);
+          else
+            L.Width -= zext;
+        }
       }
 
       return L;
@@ -10009,9 +10003,9 @@
       IntRange L = GetExprRange(C, BO->getLHS(), opWidth, InConstantContext);
 
       // If the divisor is constant, use that.
-      llvm::APSInt divisor;
-      if (BO->getRHS()->isIntegerConstantExpr(divisor, C)) {
-        unsigned log2 = divisor.logBase2(); // floor(log_2(divisor))
+      if (Optional<llvm::APSInt> divisor =
+              BO->getRHS()->getIntegerConstantExpr(C)) {
+        unsigned log2 = divisor->logBase2(); // floor(log_2(divisor))
         if (log2 >= L.Width)
           L.Width = (L.NonNegative ? 0 : 1);
         else
@@ -10443,23 +10437,20 @@
   Expr *RHS = E->getRHS();
 
   if (T->isIntegralType(S.Context)) {
-    llvm::APSInt RHSValue;
-    llvm::APSInt LHSValue;
-
-    bool IsRHSIntegralLiteral = RHS->isIntegerConstantExpr(RHSValue, S.Context);
-    bool IsLHSIntegralLiteral = LHS->isIntegerConstantExpr(LHSValue, S.Context);
+    Optional<llvm::APSInt> RHSValue = RHS->getIntegerConstantExpr(S.Context);
+    Optional<llvm::APSInt> LHSValue = LHS->getIntegerConstantExpr(S.Context);
 
     // We don't care about expressions whose result is a constant.
-    if (IsRHSIntegralLiteral && IsLHSIntegralLiteral)
+    if (RHSValue && LHSValue)
       return AnalyzeImpConvsInComparison(S, E);
 
     // We only care about expressions where just one side is literal
-    if (IsRHSIntegralLiteral ^ IsLHSIntegralLiteral) {
+    if ((bool)RHSValue ^ (bool)LHSValue) {
       // Is the constant on the RHS or LHS?
-      const bool RhsConstant = IsRHSIntegralLiteral;
+      const bool RhsConstant = (bool)RHSValue;
       Expr *Const = RhsConstant ? RHS : LHS;
       Expr *Other = RhsConstant ? LHS : RHS;
-      const llvm::APSInt &Value = RhsConstant ? RHSValue : LHSValue;
+      const llvm::APSInt &Value = RhsConstant ? *RHSValue : *LHSValue;
 
       // Check whether an integer constant comparison results in a value
       // of 'true' or 'false'.
@@ -11417,8 +11408,8 @@
     if (SourcePrecision > 0 && TargetPrecision > 0 &&
         SourcePrecision > TargetPrecision) {
 
-      llvm::APSInt SourceInt;
-      if (E->isIntegerConstantExpr(SourceInt, S.Context)) {
+      if (Optional<llvm::APSInt> SourceInt =
+              E->getIntegerConstantExpr(S.Context)) {
         // If the source integer is a constant, convert it to the target
         // floating point type. Issue a warning if the value changes
         // during the whole conversion.
@@ -11426,11 +11417,11 @@
             S.Context.getFloatTypeSemantics(QualType(TargetBT, 0)));
         llvm::APFloat::opStatus ConversionStatus =
             TargetFloatValue.convertFromAPInt(
-                SourceInt, SourceBT->isSignedInteger(),
+                *SourceInt, SourceBT->isSignedInteger(),
                 llvm::APFloat::rmNearestTiesToEven);
 
         if (ConversionStatus != llvm::APFloat::opOK) {
-          std::string PrettySourceValue = SourceInt.toString(10);
+          std::string PrettySourceValue = SourceInt->toString(10);
           SmallString<32> PrettyTargetValue;
           TargetFloatValue.toString(PrettyTargetValue, TargetPrecision);
 
@@ -13385,9 +13376,10 @@
           return;
         if (Expr *RHS = BinOp->getRHS()) {
           RHS = RHS->IgnoreParenCasts();
-          llvm::APSInt Value;
+          Optional<llvm::APSInt> Value;
           VarWillBeReased =
-            (RHS && RHS->isIntegerConstantExpr(Value, Context) && Value == 0);
+              (RHS && (Value = RHS->getIntegerConstantExpr(Context)) &&
+               *Value == 0);
         }
       }
     }
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -13062,20 +13062,20 @@
     if (!MagicValueExpr) {
       continue;
     }
-    llvm::APSInt MagicValueInt;
-    if (!MagicValueExpr->isIntegerConstantExpr(MagicValueInt, Context)) {
+    Optional<llvm::APSInt> MagicValueInt;
+    if (!(MagicValueInt = MagicValueExpr->getIntegerConstantExpr( Context))) {
       Diag(I->getRange().getBegin(),
            diag::err_type_tag_for_datatype_not_ice)
         << LangOpts.CPlusPlus << MagicValueExpr->getSourceRange();
       continue;
     }
-    if (MagicValueInt.getActiveBits() > 64) {
+    if (MagicValueInt->getActiveBits() > 64) {
       Diag(I->getRange().getBegin(),
            diag::err_type_tag_for_datatype_too_large)
         << LangOpts.CPlusPlus << MagicValueExpr->getSourceRange();
       continue;
     }
-    uint64_t MagicValue = MagicValueInt.getZExtValue();
+    uint64_t MagicValue = MagicValueInt->getZExtValue();
     RegisterTypeTagForDatatype(I->getArgumentKind(),
                                MagicValue,
                                I->getMatchingCType(),
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -240,9 +240,9 @@
 static bool checkUInt32Argument(Sema &S, const AttrInfo &AI, const Expr *Expr,
                                 uint32_t &Val, unsigned Idx = UINT_MAX,
                                 bool StrictlyUnsigned = false) {
-  llvm::APSInt I(32);
+  Optional<llvm::APSInt> I = llvm::APSInt(32);
   if (Expr->isTypeDependent() || Expr->isValueDependent() ||
-      !Expr->isIntegerConstantExpr(I, S.Context)) {
+      !(I = Expr->getIntegerConstantExpr(S.Context))) {
     if (Idx != UINT_MAX)
       S.Diag(getAttrLoc(AI), diag::err_attribute_argument_n_type)
           << &AI << Idx << AANT_ArgumentIntegerConstant
@@ -253,19 +253,19 @@
     return false;
   }
 
-  if (!I.isIntN(32)) {
+  if (!I->isIntN(32)) {
     S.Diag(Expr->getExprLoc(), diag::err_ice_too_large)
-        << I.toString(10, false) << 32 << /* Unsigned */ 1;
+        << I->toString(10, false) << 32 << /* Unsigned */ 1;
     return false;
   }
 
-  if (StrictlyUnsigned && I.isSigned() && I.isNegative()) {
+  if (StrictlyUnsigned && I->isSigned() && I->isNegative()) {
     S.Diag(getAttrLoc(AI), diag::err_attribute_requires_positive_integer)
         << &AI << /*non-negative*/ 1;
     return false;
   }
 
-  Val = (uint32_t)I.getZExtValue();
+  Val = (uint32_t)I->getZExtValue();
   return true;
 }
 
@@ -332,16 +332,16 @@
   unsigned NumParams =
       (HP ? getFunctionOrMethodNumParams(D) : 0) + HasImplicitThisParam;
 
-  llvm::APSInt IdxInt;
+  Optional<llvm::APSInt> IdxInt;
   if (IdxExpr->isTypeDependent() || IdxExpr->isValueDependent() ||
-      !IdxExpr->isIntegerConstantExpr(IdxInt, S.Context)) {
+      !(IdxInt = IdxExpr->getIntegerConstantExpr(S.Context))) {
     S.Diag(getAttrLoc(AI), diag::err_attribute_argument_n_type)
         << &AI << AttrArgNum << AANT_ArgumentIntegerConstant
         << IdxExpr->getSourceRange();
     return false;
   }
 
-  unsigned IdxSource = IdxInt.getLimitedValue(UINT_MAX);
+  unsigned IdxSource = IdxInt->getLimitedValue(UINT_MAX);
   if (IdxSource < 1 || (!IV && IdxSource > NumParams)) {
     S.Diag(getAttrLoc(AI), diag::err_attribute_argument_out_of_bounds)
         << &AI << AttrArgNum << IdxExpr->getSourceRange();
@@ -1605,8 +1605,8 @@
   }
 
   if (!E->isValueDependent()) {
-    llvm::APSInt I(64);
-    if (!E->isIntegerConstantExpr(I, Context)) {
+    Optional<llvm::APSInt> I = llvm::APSInt(64);
+    if (!(I = E->getIntegerConstantExpr(Context))) {
       if (OE)
         Diag(AttrLoc, diag::err_attribute_argument_n_type)
           << &TmpAttr << 1 << AANT_ArgumentIntegerConstant
@@ -1618,27 +1618,22 @@
       return;
     }
 
-    if (!I.isPowerOf2()) {
+    if (!I->isPowerOf2()) {
       Diag(AttrLoc, diag::err_alignment_not_power_of_two)
         << E->getSourceRange();
       return;
     }
 
-    if (I > Sema::MaximumAlignment)
+    if (*I > Sema::MaximumAlignment)
       Diag(CI.getLoc(), diag::warn_assume_aligned_too_great)
           << CI.getRange() << Sema::MaximumAlignment;
   }
 
-  if (OE) {
-    if (!OE->isValueDependent()) {
-      llvm::APSInt I(64);
-      if (!OE->isIntegerConstantExpr(I, Context)) {
-        Diag(AttrLoc, diag::err_attribute_argument_n_type)
-          << &TmpAttr << 2 << AANT_ArgumentIntegerConstant
-          << OE->getSourceRange();
-        return;
-      }
-    }
+  if (OE && !OE->isValueDependent() && !OE->isIntegerConstantExpr(Context)) {
+    Diag(AttrLoc, diag::err_attribute_argument_n_type)
+        << &TmpAttr << 2 << AANT_ArgumentIntegerConstant
+        << OE->getSourceRange();
+    return;
   }
 
   D->addAttr(::new (Context) AssumeAlignedAttr(Context, CI, E, OE));
@@ -2714,36 +2709,36 @@
   unsigned sentinel = (unsigned)SentinelAttr::DefaultSentinel;
   if (AL.getNumArgs() > 0) {
     Expr *E = AL.getArgAsExpr(0);
-    llvm::APSInt Idx(32);
+    Optional<llvm::APSInt> Idx = llvm::APSInt(32);
     if (E->isTypeDependent() || E->isValueDependent() ||
-        !E->isIntegerConstantExpr(Idx, S.Context)) {
+        !(Idx = E->getIntegerConstantExpr(S.Context))) {
       S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
           << AL << 1 << AANT_ArgumentIntegerConstant << E->getSourceRange();
       return;
     }
 
-    if (Idx.isSigned() && Idx.isNegative()) {
+    if (Idx->isSigned() && Idx->isNegative()) {
       S.Diag(AL.getLoc(), diag::err_attribute_sentinel_less_than_zero)
         << E->getSourceRange();
       return;
     }
 
-    sentinel = Idx.getZExtValue();
+    sentinel = Idx->getZExtValue();
   }
 
   unsigned nullPos = (unsigned)SentinelAttr::DefaultNullPos;
   if (AL.getNumArgs() > 1) {
     Expr *E = AL.getArgAsExpr(1);
-    llvm::APSInt Idx(32);
+    Optional<llvm::APSInt> Idx = llvm::APSInt(32);
     if (E->isTypeDependent() || E->isValueDependent() ||
-        !E->isIntegerConstantExpr(Idx, S.Context)) {
+        !(Idx = E->getIntegerConstantExpr(S.Context))) {
       S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
           << AL << 2 << AANT_ArgumentIntegerConstant << E->getSourceRange();
       return;
     }
-    nullPos = Idx.getZExtValue();
+    nullPos = Idx->getZExtValue();
 
-    if ((Idx.isSigned() && Idx.isNegative()) || nullPos > 1) {
+    if ((Idx->isSigned() && Idx->isNegative()) || nullPos > 1) {
       // FIXME: This error message could be improved, it would be nice
       // to say what the bounds actually are.
       S.Diag(AL.getLoc(), diag::err_attribute_sentinel_not_zero_or_one)
@@ -4797,19 +4792,19 @@
   if (E->isValueDependent())
     return E;
 
-  llvm::APSInt I(64);
-  if (!E->isIntegerConstantExpr(I, S.Context)) {
+  Optional<llvm::APSInt> I = llvm::APSInt(64);
+  if (!(I = E->getIntegerConstantExpr(S.Context))) {
     S.Diag(E->getExprLoc(), diag::err_attribute_argument_n_type)
         << &AL << Idx << AANT_ArgumentIntegerConstant << E->getSourceRange();
     return nullptr;
   }
   // Make sure we can fit it in 32 bits.
-  if (!I.isIntN(32)) {
-    S.Diag(E->getExprLoc(), diag::err_ice_too_large) << I.toString(10, false)
+  if (!I->isIntN(32)) {
+    S.Diag(E->getExprLoc(), diag::err_ice_too_large) << I->toString(10, false)
                                                      << 32 << /* Unsigned */ 1;
     return nullptr;
   }
-  if (I < 0)
+  if (*I < 0)
     S.Diag(E->getExprLoc(), diag::warn_attribute_argument_n_negative)
         << &AL << Idx << E->getSourceRange();
 
@@ -5639,18 +5634,18 @@
   }
 
   Expr *NumParamsExpr = static_cast<Expr *>(AL.getArgAsExpr(0));
-  llvm::APSInt NumParams(32);
-  if (!NumParamsExpr->isIntegerConstantExpr(NumParams, S.Context)) {
+  Optional<llvm::APSInt> NumParams = llvm::APSInt(32);
+  if (!(NumParams = NumParamsExpr->getIntegerConstantExpr(S.Context))) {
     S.Diag(AL.getLoc(), diag::err_attribute_argument_type)
         << AL << AANT_ArgumentIntegerConstant
         << NumParamsExpr->getSourceRange();
     return;
   }
   // The argument should be in range 0..63.
-  unsigned Num = NumParams.getLimitedValue(255);
+  unsigned Num = NumParams->getLimitedValue(255);
   if (Num > 63) {
     S.Diag(AL.getLoc(), diag::err_attribute_argument_out_of_bounds)
-        << AL << (int)NumParams.getSExtValue()
+        << AL << (int)NumParams->getSExtValue()
         << NumParamsExpr->getSourceRange();
     return;
   }
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -2083,14 +2083,13 @@
     // per CWG1464. Otherwise, if it's not a constant, we must have an
     // unparenthesized array type.
     if (!(*ArraySize)->isValueDependent()) {
-      llvm::APSInt Value;
       // We've already performed any required implicit conversion to integer or
       // unscoped enumeration type.
       // FIXME: Per CWG1464, we are required to check the value prior to
       // converting to size_t. This will never find a negative array size in
       // C++14 onwards, because Value is always unsigned here!
-      if ((*ArraySize)->isIntegerConstantExpr(Value, Context)) {
-        if (Value.isSigned() && Value.isNegative()) {
+      if (Optional<llvm::APSInt> Value = (*ArraySize)->getIntegerConstantExpr(Context)) {
+        if (Value->isSigned() && Value->isNegative()) {
           return ExprError(Diag((*ArraySize)->getBeginLoc(),
                                 diag::err_typecheck_negative_array_size)
                            << (*ArraySize)->getSourceRange());
@@ -2098,14 +2097,14 @@
 
         if (!AllocType->isDependentType()) {
           unsigned ActiveSizeBits =
-            ConstantArrayType::getNumAddressingBits(Context, AllocType, Value);
+            ConstantArrayType::getNumAddressingBits(Context, AllocType, *Value);
           if (ActiveSizeBits > ConstantArrayType::getMaxSizeBits(Context))
             return ExprError(
                 Diag((*ArraySize)->getBeginLoc(), diag::err_array_too_large)
-                << Value.toString(10) << (*ArraySize)->getSourceRange());
+                << Value->toString(10) << (*ArraySize)->getSourceRange());
         }
 
-        KnownArraySize = Value.getZExtValue();
+        KnownArraySize = Value->getZExtValue();
       } else if (TypeIdParens.isValid()) {
         // Can't have dynamic array size when the type-id is in parentheses.
         Diag((*ArraySize)->getBeginLoc(), diag::ext_new_paren_array_nonconst)
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -5504,8 +5504,7 @@
   // Deal with non-constant score and user condition expressions.
   auto HandleNonConstantScoresAndConditions = [this](Expr *&E,
                                                      bool IsScore) -> bool {
-    llvm::APSInt Result;
-    if (!E || E->isIntegerConstantExpr(Result, Context))
+    if (!E || E->isIntegerConstantExpr(Context))
       return false;
 
     if (IsScore) {
@@ -6009,14 +6008,14 @@
     //  loop. If test-expr is of form b relational-op var and relational-op is
     //  > or >= then incr-expr must cause var to increase on each iteration of
     //  the loop.
-    llvm::APSInt Result;
-    bool IsConstant = NewStep->isIntegerConstantExpr(Result, SemaRef.Context);
+    Optional<llvm::APSInt> Result =
+        NewStep->getIntegerConstantExpr(SemaRef.Context);
     bool IsUnsigned = !NewStep->getType()->hasSignedIntegerRepresentation();
     bool IsConstNeg =
-        IsConstant && Result.isSigned() && (Subtract != Result.isNegative());
+        Result && Result->isSigned() && (Subtract != Result->isNegative());
     bool IsConstPos =
-        IsConstant && Result.isSigned() && (Subtract == Result.isNegative());
-    bool IsConstZero = IsConstant && !Result.getBoolValue();
+        Result && Result->isSigned() && (Subtract == Result->isNegative());
+    bool IsConstZero = Result && !Result->getBoolValue();
 
     // != with increment is treated as <; != with decrement is treated as >
     if (!TestIsLessOp.hasValue())
@@ -7353,9 +7352,8 @@
 static bool fitsInto(unsigned Bits, bool Signed, const Expr *E, Sema &SemaRef) {
   if (E == nullptr)
     return false;
-  llvm::APSInt Result;
-  if (E->isIntegerConstantExpr(Result, SemaRef.Context))
-    return Signed ? Result.isSignedIntN(Bits) : Result.isIntN(Bits);
+  if (Optional<llvm::APSInt> Result = E->getIntegerConstantExpr(SemaRef.Context))
+    return Signed ? Result->isSignedIntN(Bits) : Result->isIntN(Bits);
   return false;
 }
 
@@ -7628,9 +7626,7 @@
 
   // Calculate the last iteration number beforehand instead of doing this on
   // each iteration. Do not do this if the number of iterations may be kfold-ed.
-  llvm::APSInt Result;
-  bool IsConstant =
-      LastIteration.get()->isIntegerConstantExpr(Result, SemaRef.Context);
+  bool IsConstant = LastIteration.get()->isIntegerConstantExpr(SemaRef.Context);
   ExprResult CalcLastIteration;
   if (!IsConstant) {
     ExprResult SaveRef =
@@ -11953,15 +11949,16 @@
 
     ValExpr = Value.get();
     // The expression must evaluate to a non-negative integer value.
-    llvm::APSInt Result;
-    if (ValExpr->isIntegerConstantExpr(Result, SemaRef.Context) &&
-        Result.isSigned() &&
-        !((!StrictlyPositive && Result.isNonNegative()) ||
-          (StrictlyPositive && Result.isStrictlyPositive()))) {
-      SemaRef.Diag(Loc, diag::err_omp_negative_expression_in_clause)
-          << getOpenMPClauseName(CKind) << (StrictlyPositive ? 1 : 0)
-          << ValExpr->getSourceRange();
-      return false;
+    if (Optional<llvm::APSInt> Result =
+            ValExpr->getIntegerConstantExpr(SemaRef.Context)) {
+      if (Result->isSigned() &&
+          !((!StrictlyPositive && Result->isNonNegative()) ||
+            (StrictlyPositive && Result->isStrictlyPositive()))) {
+        SemaRef.Diag(Loc, diag::err_omp_negative_expression_in_clause)
+            << getOpenMPClauseName(CKind) << (StrictlyPositive ? 1 : 0)
+            << ValExpr->getSourceRange();
+        return false;
+      }
     }
     if (!BuildCapture)
       return true;
@@ -12577,9 +12574,9 @@
       // OpenMP [2.7.1, Restrictions]
       //  chunk_size must be a loop invariant integer expression with a positive
       //  value.
-      llvm::APSInt Result;
-      if (ValExpr->isIntegerConstantExpr(Result, Context)) {
-        if (Result.isSigned() && !Result.isStrictlyPositive()) {
+      if (Optional<llvm::APSInt> Result =
+              ValExpr->getIntegerConstantExpr(Context)) {
+        if (Result->isSigned() && !Result->isStrictlyPositive()) {
           Diag(ChunkSizeLoc, diag::err_omp_negative_expression_in_clause)
               << "schedule" << 1 << ChunkSize->getSourceRange();
           return nullptr;
@@ -14930,12 +14927,12 @@
 
     // Warn about zero linear step (it would be probably better specified as
     // making corresponding variables 'const').
-    llvm::APSInt Result;
-    bool IsConstant = StepExpr->isIntegerConstantExpr(Result, Context);
-    if (IsConstant && !Result.isNegative() && !Result.isStrictlyPositive())
-      Diag(StepLoc, diag::warn_omp_linear_step_zero) << Vars[0]
-                                                     << (Vars.size() > 1);
-    if (!IsConstant && CalcStep.isUsable()) {
+    if (Optional<llvm::APSInt> Result =
+            StepExpr->getIntegerConstantExpr(Context)) {
+      if (!Result->isNegative() && !Result->isStrictlyPositive())
+        Diag(StepLoc, diag::warn_omp_linear_step_zero)
+            << Vars[0] << (Vars.size() > 1);
+    } else if (CalcStep.isUsable()) {
       // Calculate the step beforehand instead of doing this on each iteration.
       // (This is not used if the number of iterations may be kfold-ed).
       CalcStepExpr = CalcStep.get();
@@ -17414,9 +17411,9 @@
       // OpenMP [2.7.1, Restrictions]
       //  chunk_size must be a loop invariant integer expression with a positive
       //  value.
-      llvm::APSInt Result;
-      if (ValExpr->isIntegerConstantExpr(Result, Context)) {
-        if (Result.isSigned() && !Result.isStrictlyPositive()) {
+      if (Optional<llvm::APSInt> Result =
+              ValExpr->getIntegerConstantExpr(Context)) {
+        if (Result->isSigned() && !Result->isStrictlyPositive()) {
           Diag(ChunkSizeLoc, diag::err_omp_negative_expression_in_clause)
               << "dist_schedule" << ChunkSize->getSourceRange();
           return nullptr;
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -346,7 +346,6 @@
                ToType->isRealFloatingType()) {
       if (IgnoreFloatToIntegralConversion)
         return NK_Not_Narrowing;
-      llvm::APSInt IntConstantValue;
       const Expr *Initializer = IgnoreNarrowingConversion(Ctx, Converted);
       assert(Initializer && "Unknown conversion expression");
 
@@ -354,19 +353,20 @@
       if (Initializer->isValueDependent())
         return NK_Dependent_Narrowing;
 
-      if (Initializer->isIntegerConstantExpr(IntConstantValue, Ctx)) {
+      if (Optional<llvm::APSInt> IntConstantValue =
+              Initializer->getIntegerConstantExpr(Ctx)) {
         // Convert the integer to the floating type.
         llvm::APFloat Result(Ctx.getFloatTypeSemantics(ToType));
-        Result.convertFromAPInt(IntConstantValue, IntConstantValue.isSigned(),
+        Result.convertFromAPInt(*IntConstantValue, IntConstantValue->isSigned(),
                                 llvm::APFloat::rmNearestTiesToEven);
         // And back.
-        llvm::APSInt ConvertedValue = IntConstantValue;
+        llvm::APSInt ConvertedValue = *IntConstantValue;
         bool ignored;
         Result.convertToInteger(ConvertedValue,
                                 llvm::APFloat::rmTowardZero, &ignored);
         // If the resulting value is different, this was a narrowing conversion.
-        if (IntConstantValue != ConvertedValue) {
-          ConstantValue = APValue(IntConstantValue);
+        if (*IntConstantValue != ConvertedValue) {
+          ConstantValue = APValue(*IntConstantValue);
           ConstantType = Initializer->getType();
           return NK_Constant_Narrowing;
         }
@@ -430,17 +430,18 @@
         (FromWidth == ToWidth && FromSigned != ToSigned) ||
         (FromSigned && !ToSigned)) {
       // Not all values of FromType can be represented in ToType.
-      llvm::APSInt InitializerValue;
       const Expr *Initializer = IgnoreNarrowingConversion(Ctx, Converted);
 
       // If it's value-dependent, we can't tell whether it's narrowing.
       if (Initializer->isValueDependent())
         return NK_Dependent_Narrowing;
 
-      if (!Initializer->isIntegerConstantExpr(InitializerValue, Ctx)) {
+      Optional<llvm::APSInt> OptInitializerValue;
+      if (!(OptInitializerValue = Initializer->getIntegerConstantExpr(Ctx))) {
         // Such conversions on variables are always narrowing.
         return NK_Variable_Narrowing;
       }
+      llvm::APSInt& InitializerValue = *OptInitializerValue;
       bool Narrowing = false;
       if (FromWidth < ToWidth) {
         // Negative -> unsigned is narrowing. Otherwise, more bits is never
@@ -2175,21 +2176,21 @@
   // compatibility.
   if (From) {
     if (FieldDecl *MemberDecl = From->getSourceBitField()) {
-      llvm::APSInt BitWidth;
+      Optional<llvm::APSInt> BitWidth;
       if (FromType->isIntegralType(Context) &&
-          MemberDecl->getBitWidth()->isIntegerConstantExpr(BitWidth, Context)) {
-        llvm::APSInt ToSize(BitWidth.getBitWidth(), BitWidth.isUnsigned());
+          (BitWidth = MemberDecl->getBitWidth()->getIntegerConstantExpr(Context))) {
+        llvm::APSInt ToSize(BitWidth->getBitWidth(), BitWidth->isUnsigned());
         ToSize = Context.getTypeSize(ToType);
 
         // Are we promoting to an int from a bitfield that fits in an int?
-        if (BitWidth < ToSize ||
-            (FromType->isSignedIntegerType() && BitWidth <= ToSize)) {
+        if (*BitWidth < ToSize ||
+            (FromType->isSignedIntegerType() && *BitWidth <= ToSize)) {
           return To->getKind() == BuiltinType::Int;
         }
 
         // Are we promoting to an unsigned int from an unsigned bitfield
         // that fits into an unsigned int?
-        if (FromType->isUnsignedIntegerType() && BitWidth <= ToSize) {
+        if (FromType->isUnsignedIntegerType() && *BitWidth <= ToSize) {
           return To->getKind() == BuiltinType::UInt;
         }
 
diff --git a/clang/lib/Sema/SemaStmtAttr.cpp b/clang/lib/Sema/SemaStmtAttr.cpp
--- a/clang/lib/Sema/SemaStmtAttr.cpp
+++ b/clang/lib/Sema/SemaStmtAttr.cpp
@@ -296,15 +296,15 @@
 
   if (NumArgs == 1) {
     Expr *E = A.getArgAsExpr(0);
-    llvm::APSInt ArgVal(32);
+    Optional<llvm::APSInt> ArgVal;
 
-    if (!E->isIntegerConstantExpr(ArgVal, S.Context)) {
+    if (!(ArgVal = E->getIntegerConstantExpr(S.Context))) {
       S.Diag(A.getLoc(), diag::err_attribute_argument_type)
           << A << AANT_ArgumentIntegerConstant << E->getSourceRange();
       return nullptr;
     }
 
-    int Val = ArgVal.getSExtValue();
+    int Val = ArgVal->getSExtValue();
 
     if (Val <= 0) {
       S.Diag(A.getRange().getBegin(),
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -2417,8 +2417,8 @@
     return Context.getDependentVectorType(CurType, SizeExpr, AttrLoc,
                                                VectorType::GenericVector);
 
-  llvm::APSInt VecSize(32);
-  if (!SizeExpr->isIntegerConstantExpr(VecSize, Context)) {
+  Optional<llvm::APSInt> VecSize = SizeExpr->getIntegerConstantExpr(Context);
+  if (!VecSize) {
     Diag(AttrLoc, diag::err_attribute_argument_type)
         << "vector_size" << AANT_ArgumentIntegerConstant
         << SizeExpr->getSourceRange();
@@ -2429,7 +2429,7 @@
     return Context.getDependentVectorType(CurType, SizeExpr, AttrLoc,
                                                VectorType::GenericVector);
 
-  unsigned VectorSize = static_cast<unsigned>(VecSize.getZExtValue() * 8);
+  unsigned VectorSize = static_cast<unsigned>(VecSize->getZExtValue() * 8);
   unsigned TypeSize = static_cast<unsigned>(Context.getTypeSize(CurType));
 
   if (VectorSize == 0) {
@@ -2474,8 +2474,8 @@
   }
 
   if (!ArraySize->isTypeDependent() && !ArraySize->isValueDependent()) {
-    llvm::APSInt vecSize(32);
-    if (!ArraySize->isIntegerConstantExpr(vecSize, Context)) {
+    Optional<llvm::APSInt> vecSize = ArraySize->getIntegerConstantExpr(Context);
+    if (!vecSize) {
       Diag(AttrLoc, diag::err_attribute_argument_type)
         << "ext_vector_type" << AANT_ArgumentIntegerConstant
         << ArraySize->getSourceRange();
@@ -2484,7 +2484,7 @@
 
     // Unlike gcc's vector_size attribute, the size is specified as the
     // number of elements, not the number of bytes.
-    unsigned vectorSize = static_cast<unsigned>(vecSize.getZExtValue());
+    unsigned vectorSize = static_cast<unsigned>(vecSize->getZExtValue());
 
     if (vectorSize == 0) {
       Diag(AttrLoc, diag::err_attribute_zero_size)
@@ -6073,13 +6073,15 @@
                                    const Expr *AddrSpace,
                                    SourceLocation AttrLoc) {
   if (!AddrSpace->isValueDependent()) {
-    llvm::APSInt addrSpace(32);
-    if (!AddrSpace->isIntegerConstantExpr(addrSpace, S.Context)) {
+    Optional<llvm::APSInt> OptAddrSpace =
+        AddrSpace->getIntegerConstantExpr(S.Context);
+    if (!OptAddrSpace) {
       S.Diag(AttrLoc, diag::err_attribute_argument_type)
           << "'address_space'" << AANT_ArgumentIntegerConstant
           << AddrSpace->getSourceRange();
       return false;
     }
+    llvm::APSInt &addrSpace = *OptAddrSpace;
 
     // Bounds checking.
     if (addrSpace.isSigned()) {
@@ -7510,9 +7512,9 @@
   }
   // The number of elements must be an ICE.
   Expr *numEltsExpr = static_cast<Expr *>(Attr.getArgAsExpr(0));
-  llvm::APSInt numEltsInt(32);
+  Optional<llvm::APSInt> numEltsInt;
   if (numEltsExpr->isTypeDependent() || numEltsExpr->isValueDependent() ||
-      !numEltsExpr->isIntegerConstantExpr(numEltsInt, S.Context)) {
+      !(numEltsInt = numEltsExpr->getIntegerConstantExpr(S.Context))) {
     S.Diag(Attr.getLoc(), diag::err_attribute_argument_type)
         << Attr << AANT_ArgumentIntegerConstant
         << numEltsExpr->getSourceRange();
@@ -7528,7 +7530,7 @@
 
   // The total size of the vector must be 64 or 128 bits.
   unsigned typeSize = static_cast<unsigned>(S.Context.getTypeSize(CurType));
-  unsigned numElts = static_cast<unsigned>(numEltsInt.getZExtValue());
+  unsigned numElts = static_cast<unsigned>(numEltsInt->getZExtValue());
   unsigned vecSize = typeSize * numElts;
   if (vecSize != 64 && vecSize != 128) {
     S.Diag(Attr.getLoc(), diag::err_attribute_bad_neon_vector_size) << CurType;