Index: include/clang/Basic/TargetInfo.h
===================================================================
--- include/clang/Basic/TargetInfo.h
+++ include/clang/Basic/TargetInfo.h
@@ -773,6 +773,14 @@
     return true;
   }
 
+  /// Returns true if the target doesn't support c++17's aligned new and
+  /// delete operators. For example, if the deployment target is old and the
+  /// operators are not available in the c++ standard library, this function
+  /// should return true.
+  virtual bool disableAlignedAllocation() const {
+    return false;
+  }
+
   /// \brief Returns the target triple of the primary target.
   const llvm::Triple &getTriple() const {
     return Triple;
Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -292,6 +292,29 @@
     // and therefore doesn't guarantee 16-byte alignment.
     return  64;
   }
+
+  bool disableAlignedAllocation() const override {
+    unsigned Major, Minor, Micro;
+    const llvm::Triple &T = this->getTriple();
+    T.getOSVersion(Major, Minor, Micro);
+
+    switch (T.getOS()) {
+    case llvm::Triple::Darwin:
+    case llvm::Triple::MacOSX: // Earlier than 10.13.
+      if (Major > 10)
+        return false;
+      if (Major < 10)
+        return true;
+      return Minor < 13;
+    case llvm::Triple::IOS:
+    case llvm::Triple::TvOS: // Earlier than 11.0.
+      return Major < 11;
+    case llvm::Triple::WatchOS: // Earlier than 4.0.
+      return Major < 4;
+    default:
+      llvm_unreachable("unexpected OS");
+    }
+  }
 };
 
 
Index: lib/Sema/SemaExprCXX.cpp
===================================================================
--- lib/Sema/SemaExprCXX.cpp
+++ lib/Sema/SemaExprCXX.cpp
@@ -2580,7 +2580,8 @@
     // Create up to four variants of the function (sized/aligned).
     bool HasSizedVariant = getLangOpts().SizedDeallocation &&
                            (Kind == OO_Delete || Kind == OO_Array_Delete);
-    bool HasAlignedVariant = getLangOpts().AlignedAllocation;
+    bool HasAlignedVariant = getLangOpts().AlignedAllocation &&
+                             !Context.getTargetInfo().disableAlignedAllocation();
 
     int NumSizeVariants = (HasSizedVariant ? 2 : 1);
     int NumAlignVariants = (HasAlignedVariant ? 2 : 1);
Index: test/CodeGenCXX/cxx1z-aligned-allocation.cpp
===================================================================
--- test/CodeGenCXX/cxx1z-aligned-allocation.cpp
+++ test/CodeGenCXX/cxx1z-aligned-allocation.cpp
@@ -3,10 +3,15 @@
 // RUN: %clang_cc1 -std=c++11 -fexceptions -fsized-deallocation -faligned-allocation %s -emit-llvm -triple x86_64-linux-gnu -o - | FileCheck %s
 // RUN: %clang_cc1 -std=c++14 -fexceptions -fsized-deallocation -faligned-allocation %s -emit-llvm -triple x86_64-linux-gnu -o - | FileCheck %s
 // RUN: %clang_cc1 -std=c++1z -fexceptions -fsized-deallocation %s -emit-llvm -triple x86_64-linux-gnu -o - | FileCheck %s
+// RUN: %clang_cc1 -std=c++1z -fexceptions -fsized-deallocation %s -emit-llvm -triple x86_64-apple-darwin10.13 -o - | FileCheck %s
 
 // Check that we don't used aligned (de)allocation without -faligned-allocation or C++1z.
 // RUN: %clang_cc1 -std=c++14 -DUNALIGNED -fexceptions %s -emit-llvm -triple x86_64-linux-gnu -o - | FileCheck %s --check-prefix=CHECK-UNALIGNED
 // RUN: %clang_cc1 -std=c++1z -DUNALIGNED -fexceptions -fno-aligned-allocation %s -emit-llvm -triple x86_64-linux-gnu -o - | FileCheck %s --check-prefix=CHECK-UNALIGNED
+// RUN: %clang_cc1 -std=c++1z -DUNALIGNED -fexceptions -fno-aligned-allocation %s -emit-llvm -triple x86_64-apple-darwin10.12 -o - | FileCheck %s --check-prefix=CHECK-UNALIGNED
+// RUN: %clang_cc1 -std=c++1z -DUNALIGNED -fexceptions -fno-aligned-allocation %s -emit-llvm -triple arm64-apple-ios10 -o - | FileCheck %s --check-prefix=CHECK-UNALIGNED
+// RUN: %clang_cc1 -std=c++1z -DUNALIGNED -fexceptions -fno-aligned-allocation %s -emit-llvm -triple arm64-apple-tvos10 -o - | FileCheck %s --check-prefix=CHECK-UNALIGNED
+// RUN: %clang_cc1 -std=c++1z -DUNALIGNED -fexceptions -fno-aligned-allocation %s -emit-llvm -triple thumbv7k-apple-watchos4 -o - | FileCheck %s --check-prefix=CHECK-UNALIGNED
 
 // CHECK-UNALIGNED-NOT: _Znwm_St11align_val_t
 // CHECK-UNALIGNED-NOT: _Znam_St11align_val_t