Index: include/clang/Basic/Builtins.def
===================================================================
--- include/clang/Basic/Builtins.def
+++ include/clang/Basic/Builtins.def
@@ -876,7 +876,8 @@
 LANGBUILTIN(__fastfail, "vUi",    "nr", ALL_MS_LANGUAGES)
 
 // Microsoft library builtins.
-LIBBUILTIN(_setjmpex, "iJ", "fj",   "setjmpex.h", ALL_MS_LANGUAGES)
+LIBBUILTIN(_setjmpex, "iJ",         "fj", "setjmpex.h", ALL_MS_LANGUAGES)
+LIBBUILTIN(memccpy,   "v*v*vC*iz",  "f",  "string.h",   ALL_MS_LANGUAGES)
 
 // C99 library functions
 // C99 stdarg.h
@@ -979,6 +980,7 @@
 // when these functions are used in non-GNU mode. PR16138.
 LIBBUILTIN(alloca, "v*z",         "f",     "stdlib.h", ALL_GNU_LANGUAGES)
 // POSIX string.h
+LIBBUILTIN(memccpy, "v*v*vC*iz",  "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(stpcpy, "c*c*cC*",     "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(stpncpy, "c*c*cC*z",   "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(strdup, "c*cC*",       "f",     "string.h", ALL_GNU_LANGUAGES)
Index: test/CodeGen/builtin-memfns.c
===================================================================
--- test/CodeGen/builtin-memfns.c
+++ test/CodeGen/builtin-memfns.c
@@ -4,6 +4,7 @@
 typedef __SIZE_TYPE__ size_t;
 
 void *memcpy(void *, void const *, size_t);
+void *memccpy(void *, void const *, int, size_t);
 
 // CHECK: @test1
 // CHECK: call void @llvm.memset.p0i8.i32
@@ -118,3 +119,9 @@
   // CHECK: call void @llvm.memcpy{{.*}}(
   memcpy(&dest_array, &dest_array, 2);
 }
+
+// CHECK-LABEL: @test13
+void test13(char *d, char *s, int c, size_t n) {
+  // CHECK: call i8* @memccpy
+  memccpy(d, s, c, n);
+}
Index: test/CodeGen/memccpy-libcall.c
===================================================================
--- test/CodeGen/memccpy-libcall.c
+++ test/CodeGen/memccpy-libcall.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fno-builtin-memccpy -emit-llvm < %s| FileCheck %s
+
+typedef __SIZE_TYPE__ size_t;
+
+void *memccpy(void *, void const *, int, size_t);
+
+void test13(char *d, char *s, int c, size_t n) {
+  // CHECK: call i8* @memccpy{{.*}} #2
+  memccpy(d, s, c, n);
+}
+
+// CHECK: attributes #2 = { nobuiltin }