diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.h b/llvm/include/llvm/IR/RuntimeLibcalls.h
index 0afe32a4ecc3c..adc0c777f0030 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.h
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.h
@@ -209,6 +209,16 @@ struct RuntimeLibcallsInfo {
     return true;
   }
 
+  static bool darwinHasMemsetPattern(const Triple &TT) {
+    // memset_pattern{4,8,16} is only available on iOS 3.0 and Mac OS X 10.5 and
+    // later. All versions of watchOS support it.
+    if (TT.isMacOSX())
+      return !TT.isMacOSXVersionLT(10, 5);
+    if (TT.isiOS())
+      return !TT.isOSVersionLT(3, 0);
+    return TT.isWatchOS();
+  }
+
   static bool hasAEABILibcalls(const Triple &TT) {
     return TT.isTargetAEABI() || TT.isTargetGNUAEABI() ||
            TT.isTargetMuslAEABI() || TT.isOSFuchsia() || TT.isAndroid();
diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.td b/llvm/include/llvm/IR/RuntimeLibcalls.td
index 36dea547651c9..794ab2449bc01 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.td
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.td
@@ -50,6 +50,7 @@ def isWindowsMSVCOrItaniumEnvironment : RuntimeLibcallPredicate<
 def isGNUEnvironment : RuntimeLibcallPredicate<"TT.isGNUEnvironment()">;
 def darwinHasSinCosStret : RuntimeLibcallPredicate<"darwinHasSinCosStret(TT)">;
 def darwinHasExp10 : RuntimeLibcallPredicate<"darwinHasExp10(TT)">;
+def darwinHasMemsetPattern : RuntimeLibcallPredicate<[{darwinHasMemsetPattern(TT)}]>;
 
 def hasExp10 : RuntimeLibcallPredicate<[{!TT.isOSDarwin()}]>;
 
@@ -1976,6 +1977,11 @@ defvar DarwinSinCosStret = LibcallImpls<(add __sincosf_stret, __sincos_stret,
                                         darwinHasSinCosStret>;
 defvar DarwinExp10 = LibcallImpls<(add __exp10f, __exp10), darwinHasExp10>;
 
+defvar DarwinMemsetPattern = LibcallImpls<(add memset_pattern4,
+                                               memset_pattern8,
+                                               memset_pattern16),
+                                               darwinHasMemsetPattern>;
+
 defvar SecurityCheckCookieIfWinMSVC =
     LibcallImpls<(add __security_check_cookie, __security_cookie),
                  isWindowsMSVCOrItaniumEnvironment>;
@@ -2133,7 +2139,7 @@ def AArch64SystemLibrary : SystemRuntimeLibrary<
        AArch64LibcallImpls,
        LibcallImpls<(add Int128RTLibcalls), isAArch64_ILP64>,
        LibcallImpls<(add bzero), isOSDarwin>,
-       DarwinExp10, DarwinSinCosStret,
+       DarwinExp10, DarwinSinCosStret, DarwinMemsetPattern,
        LibmHasSinCosF32, LibmHasSinCosF64, LibmHasSinCosF128,
        DefaultLibmExp10,
        DefaultStackProtector,
@@ -2603,7 +2609,7 @@ def ARMSystemLibrary
            WindowARMFPIntCasts,
            SecurityCheckCookieIfWinMSVC,
            AEABIDivRemCalls,
-           DarwinSinCosStret, DarwinExp10,
+           DarwinSinCosStret, DarwinExp10, DarwinMemsetPattern,
            LibmHasSinCosF32, LibmHasSinCosF64, LibmHasSinCosF128,
            DefaultLibmExp10,
 
@@ -3288,7 +3294,7 @@ defvar MemChkLibcalls = [__memcpy_chk, __memset_chk, __memmove_chk];
 
 defvar X86CommonLibcalls =
   (add (sub WinDefaultLibcallImpls, WindowsDivRemMulLibcallOverrides, MemChkLibcalls),
-       DarwinSinCosStret, DarwinExp10,
+       DarwinSinCosStret, DarwinExp10, DarwinMemsetPattern,
        X86_F128_Libcalls,
        LibmHasSinCosF80, // FIXME: Depends on long double
        SinCosF32F64Libcalls,
diff --git a/llvm/test/Transforms/Util/DeclareRuntimeLibcalls/darwin.ll b/llvm/test/Transforms/Util/DeclareRuntimeLibcalls/darwin.ll
new file mode 100644
index 0000000000000..6c63f5902f638
--- /dev/null
+++ b/llvm/test/Transforms/Util/DeclareRuntimeLibcalls/darwin.ll
@@ -0,0 +1,22 @@
+; REQUIRES: aarch64-registered-target, arm-registered-target, x86-registered-target
+
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=i386-apple-macosx10.5 < %s | FileCheck -check-prefix=HAS-MEMSET-PATTERN %s
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=i386-apple-macosx10.4 < %s | FileCheck -check-prefix=NO-MEMSET-PATTERN %s
+
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=x86_64-apple-macosx10.5 < %s | FileCheck -check-prefix=HAS-MEMSET-PATTERN %s
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=x86_64-apple-macosx10.4 < %s | FileCheck -check-prefix=NO-MEMSET-PATTERN %s
+
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=arm64-apple-ios3 < %s | FileCheck -check-prefix=HAS-MEMSET-PATTERN %s
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=arm64-apple-ios2 < %s | FileCheck -check-prefix=NO-MEMSET-PATTERN %s
+
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=thumbv7-apple-ios3 < %s | FileCheck -check-prefix=HAS-MEMSET-PATTERN %s
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=thumbv7-apple-ios2 < %s | FileCheck -check-prefix=NO-MEMSET-PATTERN %s
+
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=arm64_32-apple-watchos < %s | FileCheck -check-prefix=HAS-MEMSET-PATTERN %s
+; RUN: opt -S -passes=declare-runtime-libcalls -mtriple=armv7k-apple-watchos < %s | FileCheck -check-prefix=HAS-MEMSET-PATTERN %s
+
+; HAS-MEMSET-PATTERN: declare void @memset_pattern16(...)
+; HAS-MEMSET-PATTERN: declare void @memset_pattern4(...)
+; HAS-MEMSET-PATTERN: declare void @memset_pattern8(...)
+
+; NO-MEMSET-PATTERN-NOT: memset_pattern