diff --git a/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cpp b/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cpp
--- a/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cpp
+++ b/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cpp
@@ -11,6 +11,8 @@
 // ASan versions of memcpy, memmove, and memset.
 //===---------------------------------------------------------------------===//
 
+#define SANITIZER_COMMON_NO_REDEFINE_BUILTINS
+
 #include "asan_interceptors_memintrinsics.h"
 
 #include "asan_interceptors.h"
diff --git a/compiler-rt/lib/asan/tests/CMakeLists.txt b/compiler-rt/lib/asan/tests/CMakeLists.txt
--- a/compiler-rt/lib/asan/tests/CMakeLists.txt
+++ b/compiler-rt/lib/asan/tests/CMakeLists.txt
@@ -28,6 +28,7 @@
   -I${COMPILER_RT_SOURCE_DIR}/lib
   -I${COMPILER_RT_SOURCE_DIR}/lib/asan
   -I${COMPILER_RT_SOURCE_DIR}/lib/sanitizer_common/tests
+  -DSANITIZER_COMMON_NO_REDEFINE_BUILTINS
   -fno-rtti
   -O2
   -Wno-format
diff --git a/compiler-rt/lib/hwasan/hwasan_interceptors.cpp b/compiler-rt/lib/hwasan/hwasan_interceptors.cpp
--- a/compiler-rt/lib/hwasan/hwasan_interceptors.cpp
+++ b/compiler-rt/lib/hwasan/hwasan_interceptors.cpp
@@ -14,6 +14,8 @@
 // sanitizer_common/sanitizer_common_interceptors.h
 //===----------------------------------------------------------------------===//
 
+#define SANITIZER_COMMON_NO_REDEFINE_BUILTINS
+
 #include "hwasan.h"
 #include "hwasan_allocator.h"
 #include "hwasan_checks.h"
diff --git a/compiler-rt/lib/interception/tests/CMakeLists.txt b/compiler-rt/lib/interception/tests/CMakeLists.txt
--- a/compiler-rt/lib/interception/tests/CMakeLists.txt
+++ b/compiler-rt/lib/interception/tests/CMakeLists.txt
@@ -17,6 +17,7 @@
   -I${COMPILER_RT_SOURCE_DIR}/include
   -I${COMPILER_RT_SOURCE_DIR}/lib
   -I${COMPILER_RT_SOURCE_DIR}/lib/interception
+  -DSANITIZER_COMMON_NO_REDEFINE_BUILTINS
   -fno-rtti
   -O2
   -Werror=sign-compare)
diff --git a/compiler-rt/lib/memprof/memprof_interceptors_memintrinsics.cpp b/compiler-rt/lib/memprof/memprof_interceptors_memintrinsics.cpp
--- a/compiler-rt/lib/memprof/memprof_interceptors_memintrinsics.cpp
+++ b/compiler-rt/lib/memprof/memprof_interceptors_memintrinsics.cpp
@@ -11,6 +11,8 @@
 // MemProf versions of memcpy, memmove, and memset.
 //===---------------------------------------------------------------------===//
 
+#define SANITIZER_COMMON_NO_REDEFINE_BUILTINS
+
 #include "memprof_interceptors_memintrinsics.h"
 
 #include "memprof_interceptors.h"
diff --git a/compiler-rt/lib/memprof/tests/CMakeLists.txt b/compiler-rt/lib/memprof/tests/CMakeLists.txt
--- a/compiler-rt/lib/memprof/tests/CMakeLists.txt
+++ b/compiler-rt/lib/memprof/tests/CMakeLists.txt
@@ -8,6 +8,7 @@
   ${COMPILER_RT_GMOCK_CFLAGS}
   ${SANITIZER_TEST_CXX_CFLAGS}
   -I${COMPILER_RT_SOURCE_DIR}/lib/
+  -DSANITIZER_COMMON_NO_REDEFINE_BUILTINS
   -O2
   -g
   -fno-rtti
diff --git a/compiler-rt/lib/msan/msan_interceptors.cpp b/compiler-rt/lib/msan/msan_interceptors.cpp
--- a/compiler-rt/lib/msan/msan_interceptors.cpp
+++ b/compiler-rt/lib/msan/msan_interceptors.cpp
@@ -14,6 +14,8 @@
 // sanitizer_common/sanitizer_common_interceptors.h
 //===----------------------------------------------------------------------===//
 
+#define SANITIZER_COMMON_NO_REDEFINE_BUILTINS
+
 #include "interception/interception.h"
 #include "msan.h"
 #include "msan_chained_origin_depot.h"
diff --git a/compiler-rt/lib/sanitizer_common/CMakeLists.txt b/compiler-rt/lib/sanitizer_common/CMakeLists.txt
--- a/compiler-rt/lib/sanitizer_common/CMakeLists.txt
+++ b/compiler-rt/lib/sanitizer_common/CMakeLists.txt
@@ -173,6 +173,7 @@
   sanitizer_procmaps.h
   sanitizer_ptrauth.h
   sanitizer_quarantine.h
+  sanitizer_redefine_builtins.h
   sanitizer_report_decorator.h
   sanitizer_ring_buffer.h
   sanitizer_signal_interceptors.inc
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors_memintrinsics.inc b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors_memintrinsics.inc
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors_memintrinsics.inc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors_memintrinsics.inc
@@ -9,6 +9,10 @@
 // Memintrinsic function interceptors for tools like AddressSanitizer,
 // ThreadSanitizer, MemorySanitizer, etc.
 //
+// These interceptors are part of the common interceptors, but separated out so
+// that implementations may add them, if necessary, to a separate source file
+// that should define SANITIZER_COMMON_NO_REDEFINE_BUILTINS at the top.
+//
 // This file should be included into the tool's memintrinsic interceptor file,
 // which has to define its own macros:
 //   COMMON_INTERCEPTOR_ENTER
@@ -20,6 +24,10 @@
 //   COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED
 //===----------------------------------------------------------------------===//
 
+#ifdef SANITIZER_REDEFINE_BUILTINS_H
+#error "Define SANITIZER_COMMON_NO_REDEFINE_BUILTINS in .cpp file"
+#endif
+
 #include "interception/interception.h"
 #include "sanitizer_platform_interceptors.h"
 
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common_interface.inc b/compiler-rt/lib/sanitizer_common/sanitizer_common_interface.inc
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common_interface.inc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_common_interface.inc
@@ -46,3 +46,7 @@
 INTERFACE_FUNCTION(__sanitizer_print_memory_profile)
 INTERFACE_WEAK_FUNCTION(__sanitizer_free_hook)
 INTERFACE_WEAK_FUNCTION(__sanitizer_malloc_hook)
+// Memintrinsic functions.
+INTERFACE_FUNCTION(__sanitizer_internal_memcpy)
+INTERFACE_FUNCTION(__sanitizer_internal_memmove)
+INTERFACE_FUNCTION(__sanitizer_internal_memset)
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h b/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h
--- a/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h
@@ -13,6 +13,7 @@
 #define SANITIZER_DEFS_H
 
 #include "sanitizer_platform.h"
+#include "sanitizer_redefine_builtins.h"
 
 #ifndef SANITIZER_DEBUG
 # define SANITIZER_DEBUG 0
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_libc.h b/compiler-rt/lib/sanitizer_common/sanitizer_libc.h
--- a/compiler-rt/lib/sanitizer_common/sanitizer_libc.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_libc.h
@@ -24,15 +24,33 @@
 
 // internal_X() is a custom implementation of X() for use in RTL.
 
+extern "C" {
+// These are used as builtin replacements; see sanitizer_redefine_builtins.h.
+// In normal runtime code, use the __sanitizer::internal_X() aliases instead.
+SANITIZER_INTERFACE_ATTRIBUTE void *__sanitizer_internal_memcpy(void *dest,
+                                                                const void *src,
+                                                                uptr n);
+SANITIZER_INTERFACE_ATTRIBUTE void *__sanitizer_internal_memmove(
+    void *dest, const void *src, uptr n);
+SANITIZER_INTERFACE_ATTRIBUTE void *__sanitizer_internal_memset(void *s, int c,
+                                                                uptr n);
+}  // extern "C"
+
 // String functions
 s64 internal_atoll(const char *nptr);
 void *internal_memchr(const void *s, int c, uptr n);
 void *internal_memrchr(const void *s, int c, uptr n);
 int internal_memcmp(const void* s1, const void* s2, uptr n);
-void *internal_memcpy(void *dest, const void *src, uptr n);
-void *internal_memmove(void *dest, const void *src, uptr n);
+ALWAYS_INLINE void *internal_memcpy(void *dest, const void *src, uptr n) {
+  return __sanitizer_internal_memcpy(dest, src, n);
+}
+ALWAYS_INLINE void *internal_memmove(void *dest, const void *src, uptr n) {
+  return __sanitizer_internal_memmove(dest, src, n);
+}
 // Should not be used in performance-critical places.
-void *internal_memset(void *s, int c, uptr n);
+ALWAYS_INLINE void *internal_memset(void *s, int c, uptr n) {
+  return __sanitizer_internal_memset(s, c, n);
+}
 char* internal_strchr(const char *s, int c);
 char *internal_strchrnul(const char *s, int c);
 int internal_strcmp(const char *s1, const char *s2);
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_libc.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_libc.cpp
--- a/compiler-rt/lib/sanitizer_common/sanitizer_libc.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_libc.cpp
@@ -10,6 +10,9 @@
 // run-time libraries. See sanitizer_libc.h for details.
 //===----------------------------------------------------------------------===//
 
+// Do not redefine builtins; this file is defining the builtin replacements.
+#define SANITIZER_COMMON_NO_REDEFINE_BUILTINS
+
 #include "sanitizer_allocator_internal.h"
 #include "sanitizer_common.h"
 #include "sanitizer_libc.h"
@@ -46,7 +49,10 @@
   return 0;
 }
 
-void *internal_memcpy(void *dest, const void *src, uptr n) {
+extern "C" {
+SANITIZER_INTERFACE_ATTRIBUTE void *__sanitizer_internal_memcpy(void *dest,
+                                                                const void *src,
+                                                                uptr n) {
   char *d = (char*)dest;
   const char *s = (const char *)src;
   for (uptr i = 0; i < n; ++i)
@@ -54,7 +60,8 @@
   return dest;
 }
 
-void *internal_memmove(void *dest, const void *src, uptr n) {
+SANITIZER_INTERFACE_ATTRIBUTE void *__sanitizer_internal_memmove(
+    void *dest, const void *src, uptr n) {
   char *d = (char*)dest;
   const char *s = (const char *)src;
   sptr i, signed_n = (sptr)n;
@@ -72,7 +79,8 @@
   return dest;
 }
 
-void *internal_memset(void* s, int c, uptr n) {
+SANITIZER_INTERFACE_ATTRIBUTE void *__sanitizer_internal_memset(void *s, int c,
+                                                                uptr n) {
   // Optimize for the most performance-critical case:
   if ((reinterpret_cast<uptr>(s) % 16) == 0 && (n % 16) == 0) {
     u64 *p = reinterpret_cast<u64*>(s);
@@ -95,6 +103,7 @@
   }
   return s;
 }
+}  // extern "C"
 
 uptr internal_strcspn(const char *s, const char *reject) {
   uptr i;
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_redefine_builtins.h b/compiler-rt/lib/sanitizer_common/sanitizer_redefine_builtins.h
new file mode 100644
--- /dev/null
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_redefine_builtins.h
@@ -0,0 +1,47 @@
+//===-- sanitizer_redefine_builtins.h ---------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Redefine builtin functions to use internal versions. This is needed where
+// compiler optimizations end up producing unwanted libcalls!
+//
+//===----------------------------------------------------------------------===//
+#ifndef SANITIZER_COMMON_NO_REDEFINE_BUILTINS
+#ifndef SANITIZER_REDEFINE_BUILTINS_H
+#define SANITIZER_REDEFINE_BUILTINS_H
+
+// The asm hack only works with GCC and Clang.
+#if !defined(_MSC_VER) || defined(__clang__)
+
+asm("memcpy = __sanitizer_internal_memcpy");
+asm("memmove = __sanitizer_internal_memmove");
+asm("memset = __sanitizer_internal_memset");
+
+// The builtins should not be redefined in source files that make use of C++
+// standard libraries, in particular where C++STL headers with inline functions
+// are used. The redefinition in such cases would lead to ODR violations.
+//
+// Try to break the build in common cases where builtins shouldn't be redefined.
+namespace std {
+class Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file {};
+using array = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using atomic = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using function = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using map = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using set = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using shared_ptr = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using string = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using unique_ptr = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using unordered_map = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using unordered_set = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+using vector = Define_SANITIZER_COMMON_NO_REDEFINE_BUILTINS_in_cpp_file;
+}  // namespace std
+
+#endif  // !_MSC_VER || __clang__
+
+#endif  // SANITIZER_REDEFINE_BUILTINS_H
+#endif  // SANITIZER_COMMON_NO_REDEFINE_BUILTINS
diff --git a/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt b/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
--- a/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
+++ b/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
@@ -70,6 +70,7 @@
   -I${COMPILER_RT_SOURCE_DIR}/include
   -I${COMPILER_RT_SOURCE_DIR}/lib
   -I${COMPILER_RT_SOURCE_DIR}/lib/sanitizer_common
+  -DSANITIZER_COMMON_NO_REDEFINE_BUILTINS
   -fno-rtti
   -O2
   -Werror=sign-compare
diff --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors_memintrinsics.cpp b/compiler-rt/lib/tsan/rtl/tsan_interceptors_memintrinsics.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors_memintrinsics.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors_memintrinsics.cpp
@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#define SANITIZER_COMMON_NO_REDEFINE_BUILTINS
+
 #include "tsan_interceptors.h"
 #include "tsan_interface.h"
 
diff --git a/compiler-rt/lib/ubsan_minimal/CMakeLists.txt b/compiler-rt/lib/ubsan_minimal/CMakeLists.txt
--- a/compiler-rt/lib/ubsan_minimal/CMakeLists.txt
+++ b/compiler-rt/lib/ubsan_minimal/CMakeLists.txt
@@ -6,7 +6,9 @@
 
 include_directories(..)
 
-set(UBSAN_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+set(UBSAN_CFLAGS
+  ${SANITIZER_COMMON_CFLAGS}
+  -DSANITIZER_COMMON_NO_REDEFINE_BUILTINS)
 append_rtti_flag(OFF UBSAN_CFLAGS)
 
 set(UBSAN_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS})
diff --git a/compiler-rt/lib/xray/CMakeLists.txt b/compiler-rt/lib/xray/CMakeLists.txt
--- a/compiler-rt/lib/xray/CMakeLists.txt
+++ b/compiler-rt/lib/xray/CMakeLists.txt
@@ -141,7 +141,7 @@
 set(XRAY_CFLAGS
   ${COMPILER_RT_COMMON_CFLAGS}
   ${COMPILER_RT_CXX_CFLAGS})
-set(XRAY_COMMON_DEFINITIONS XRAY_HAS_EXCEPTIONS=1)
+set(XRAY_COMMON_DEFINITIONS SANITIZER_COMMON_NO_REDEFINE_BUILTINS XRAY_HAS_EXCEPTIONS=1)
 
 # Too many existing bugs, needs cleanup.
 append_list_if(COMPILER_RT_HAS_WNO_FORMAT -Wno-format XRAY_CFLAGS)
diff --git a/compiler-rt/test/asan/TestCases/Linux/check_memcpy.c b/compiler-rt/test/asan/TestCases/Linux/check_memcpy.c
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/Linux/check_memcpy.c
@@ -0,0 +1,8 @@
+// Verify runtime doesn't contain compiler-emitted memcpy/memmove calls.
+//
+// REQUIRES: shared_unwind, x86_64-target-arch
+
+// RUN: %clang_asan -O1 %s -o %t
+// RUN: llvm-objdump -d -l %t | FileCheck --implicit-check-not="{{(callq|jmpq) .*<(__interceptor_.*)?mem(cpy|set|move)>}}" %s
+
+int main() { return 0; }
diff --git a/compiler-rt/test/msan/Linux/check_memcpy.c b/compiler-rt/test/msan/Linux/check_memcpy.c
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/msan/Linux/check_memcpy.c
@@ -0,0 +1,8 @@
+// Verify runtime doesn't contain compiler-emitted memcpy/memmove calls.
+//
+// REQUIRES: shared_unwind, x86_64-target-arch
+
+// RUN: %clang_msan -O1 %s -o %t
+// RUN: llvm-objdump -d -l %t | FileCheck --implicit-check-not="{{(callq|jmpq) .*<(__interceptor_.*)?mem(cpy|set|move)>}}" %s
+
+int main() { return 0; }
diff --git a/compiler-rt/test/tsan/Linux/check_memcpy.c b/compiler-rt/test/tsan/Linux/check_memcpy.c
--- a/compiler-rt/test/tsan/Linux/check_memcpy.c
+++ b/compiler-rt/test/tsan/Linux/check_memcpy.c
@@ -5,16 +5,9 @@
 // This could fail if using a static libunwind because that static libunwind
 // could be uninstrumented and contain memcpy/memmove calls not intercepted by
 // tsan.
-// REQUIRES: shared_unwind
+// REQUIRES: shared_unwind, x86_64-target-arch
 
 // RUN: %clang_tsan -O1 %s -o %t
-// RUN: llvm-objdump -d -l %t | FileCheck %s
-
-int main() {
-  return 0;
-}
-
-// CHECK-NOT: callq {{.*<(__interceptor_)?mem(cpy|set)>}}
-// tail calls:
-// CHECK-NOT: jmpq {{.*<(__interceptor_)?mem(cpy|set)>}}
+// RUN: llvm-objdump -d -l %t | FileCheck --implicit-check-not="{{(callq|jmpq) .*<(__interceptor_.*)?mem(cpy|set|move)>}}" %s
 
+int main() { return 0; }
diff --git a/llvm/utils/gn/secondary/compiler-rt/lib/sanitizer_common/BUILD.gn b/llvm/utils/gn/secondary/compiler-rt/lib/sanitizer_common/BUILD.gn
--- a/llvm/utils/gn/secondary/compiler-rt/lib/sanitizer_common/BUILD.gn
+++ b/llvm/utils/gn/secondary/compiler-rt/lib/sanitizer_common/BUILD.gn
@@ -114,6 +114,7 @@
     "sanitizer_procmaps_solaris.cpp",
     "sanitizer_ptrauth.h",
     "sanitizer_quarantine.h",
+    "sanitizer_redefine_builtins.h",
     "sanitizer_report_decorator.h",
     "sanitizer_ring_buffer.h",
     "sanitizer_solaris.cpp",