Index: compiler-rt/lib/ubsan/CMakeLists.txt
===================================================================
--- compiler-rt/lib/ubsan/CMakeLists.txt
+++ compiler-rt/lib/ubsan/CMakeLists.txt
@@ -130,15 +130,16 @@
   endif()
 
   if(COMPILER_RT_HAS_UBSAN)
-    # Initializer of standalone UBSan runtime.
     add_compiler_rt_object_libraries(RTUbsan_standalone
       ARCHS ${UBSAN_SUPPORTED_ARCH}
-      SOURCES ${UBSAN_STANDALONE_SOURCES} CFLAGS ${UBSAN_STANDALONE_CFLAGS})
+      SOURCES ${UBSAN_STANDALONE_SOURCES}
+      CFLAGS ${UBSAN_STANDALONE_CFLAGS})
 
     # Standalone UBSan runtimes.
     add_compiler_rt_runtime(clang_rt.ubsan_standalone
       STATIC
       ARCHS ${UBSAN_SUPPORTED_ARCH}
+      SOURCES ubsan_init_standalone_preinit.cc
       OBJECT_LIBS RTSanitizerCommon
               RTSanitizerCommonLibc
               RTUbsan
@@ -158,8 +159,9 @@
         SHARED
         ARCHS ${UBSAN_SUPPORTED_ARCH}
         OBJECT_LIBS RTSanitizerCommon
-                RTSanitizerCommonLibc
-                RTUbsan
+              RTSanitizerCommonLibc
+              RTUbsan
+              RTUbsan_standalone
         CFLAGS ${UBSAN_CFLAGS}
         LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS}
         LINK_LIBS ${UBSAN_DYNAMIC_LIBS}
Index: compiler-rt/lib/ubsan/ubsan_init.cc
===================================================================
--- compiler-rt/lib/ubsan/ubsan_init.cc
+++ compiler-rt/lib/ubsan/ubsan_init.cc
@@ -27,11 +27,7 @@
   return "UndefinedBehaviorSanitizer";
 }
 
-static enum {
-  UBSAN_MODE_UNKNOWN = 0,
-  UBSAN_MODE_STANDALONE,
-  UBSAN_MODE_PLUGIN
-} ubsan_mode;
+static bool ubsan_initialized;
 static StaticSpinMutex ubsan_init_mu;
 
 static void CommonInit() {
@@ -46,38 +42,24 @@
   AndroidLogInit();
   InitializeCoverage(common_flags()->coverage, common_flags()->coverage_dir);
   CommonInit();
-  ubsan_mode = UBSAN_MODE_STANDALONE;
 }
 
 void __ubsan::InitAsStandalone() {
-  if (SANITIZER_CAN_USE_PREINIT_ARRAY) {
-    CHECK_EQ(UBSAN_MODE_UNKNOWN, ubsan_mode);
-    CommonStandaloneInit();
-    return;
-  }
   SpinMutexLock l(&ubsan_init_mu);
-  CHECK_NE(UBSAN_MODE_PLUGIN, ubsan_mode);
-  if (ubsan_mode == UBSAN_MODE_UNKNOWN)
+  if (!ubsan_initialized) {
     CommonStandaloneInit();
-}
-
-void __ubsan::InitAsStandaloneIfNecessary() {
-  if (SANITIZER_CAN_USE_PREINIT_ARRAY) {
-    CHECK_NE(UBSAN_MODE_UNKNOWN, ubsan_mode);
-    return;
+    ubsan_initialized = true;
   }
-  SpinMutexLock l(&ubsan_init_mu);
-  if (ubsan_mode == UBSAN_MODE_UNKNOWN)
-    CommonStandaloneInit();
 }
 
+void __ubsan::InitAsStandaloneIfNecessary() { return InitAsStandalone(); }
+
 void __ubsan::InitAsPlugin() {
-#if !SANITIZER_CAN_USE_PREINIT_ARRAY
   SpinMutexLock l(&ubsan_init_mu);
-#endif
-  CHECK_EQ(UBSAN_MODE_UNKNOWN, ubsan_mode);
-  CommonInit();
-  ubsan_mode = UBSAN_MODE_PLUGIN;
+  if (!ubsan_initialized) {
+    CommonInit();
+    ubsan_initialized = true;
+  }
 }
 
 #endif  // CAN_SANITIZE_UB
Index: compiler-rt/lib/ubsan/ubsan_init_standalone.cc
===================================================================
--- compiler-rt/lib/ubsan/ubsan_init_standalone.cc
+++ compiler-rt/lib/ubsan/ubsan_init_standalone.cc
@@ -19,11 +19,6 @@
 #include "sanitizer_common/sanitizer_internal_defs.h"
 #include "ubsan_init.h"
 
-#if SANITIZER_CAN_USE_PREINIT_ARRAY
-__attribute__((section(".preinit_array"), used))
-void (*__local_ubsan_preinit)(void) = __ubsan::InitAsStandalone;
-#else
-// Use a dynamic initializer.
 class UbsanStandaloneInitializer {
  public:
   UbsanStandaloneInitializer() {
@@ -31,5 +26,3 @@
   }
 };
 static UbsanStandaloneInitializer ubsan_standalone_initializer;
-#endif  // SANITIZER_CAN_USE_PREINIT_ARRAY
-
Index: compiler-rt/lib/ubsan/ubsan_init_standalone_preinit.cc
===================================================================
--- compiler-rt/lib/ubsan/ubsan_init_standalone_preinit.cc
+++ compiler-rt/lib/ubsan/ubsan_init_standalone_preinit.cc
@@ -1,4 +1,5 @@
-//===-- ubsan_init_standalone.cc ------------------------------------------===//
+//===-- ubsan_init_standalone_preinit.cc
+//------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -13,23 +14,13 @@
 
 #include "ubsan_platform.h"
 #if !CAN_SANITIZE_UB
-# error "UBSan is not supported on this platform!"
+#error "UBSan is not supported on this platform!"
 #endif
 
 #include "sanitizer_common/sanitizer_internal_defs.h"
 #include "ubsan_init.h"
 
 #if SANITIZER_CAN_USE_PREINIT_ARRAY
-__attribute__((section(".preinit_array"), used))
-void (*__local_ubsan_preinit)(void) = __ubsan::InitAsStandalone;
-#else
-// Use a dynamic initializer.
-class UbsanStandaloneInitializer {
- public:
-  UbsanStandaloneInitializer() {
-    __ubsan::InitAsStandalone();
-  }
-};
-static UbsanStandaloneInitializer ubsan_standalone_initializer;
-#endif  // SANITIZER_CAN_USE_PREINIT_ARRAY
-
+__attribute__((section(".preinit_array"), used)) void (*__local_ubsan_preinit)(
+    void) = __ubsan::InitAsStandalone;
+#endif // SANITIZER_CAN_USE_PREINIT_ARRAY