diff --git a/compiler-rt/lib/asan/asan_fuchsia.cpp b/compiler-rt/lib/asan/asan_fuchsia.cpp
--- a/compiler-rt/lib/asan/asan_fuchsia.cpp
+++ b/compiler-rt/lib/asan/asan_fuchsia.cpp
@@ -198,6 +198,10 @@
   return false;
 }
 
+void FlushUnneededASanShadowMemory(uptr p, uptr size) {
+  __sanitizer_fill_shadow(p, size, 0, 0);
+}
+
 }  // namespace __asan
 
 // These are declared (in extern "C") by <zircon/sanitizer.h>.
diff --git a/compiler-rt/lib/asan/asan_linux.cpp b/compiler-rt/lib/asan/asan_linux.cpp
--- a/compiler-rt/lib/asan/asan_linux.cpp
+++ b/compiler-rt/lib/asan/asan_linux.cpp
@@ -114,6 +114,12 @@
   UNIMPLEMENTED();
 }
 
+void FlushUnneededASanShadowMemory(uptr p, uptr size) {
+  // Since asan's mapping is compacting, the shadow chunk may be
+  // not page-aligned, so we only flush the page-aligned portion.
+  ReleaseMemoryPagesToOS(MemToShadow(p), MemToShadow(p + size));
+}
+
 #if SANITIZER_ANDROID
 // FIXME: should we do anything for Android?
 void AsanCheckDynamicRTPrereqs() {}
diff --git a/compiler-rt/lib/asan/asan_mac.cpp b/compiler-rt/lib/asan/asan_mac.cpp
--- a/compiler-rt/lib/asan/asan_mac.cpp
+++ b/compiler-rt/lib/asan/asan_mac.cpp
@@ -89,6 +89,12 @@
   op(globals, size / sizeof(__asan_global));
 }
 
+void FlushUnneededASanShadowMemory(uptr p, uptr size) {
+  // Since asan's mapping is compacting, the shadow chunk may be
+  // not page-aligned, so we only flush the page-aligned portion.
+  ReleaseMemoryPagesToOS(MemToShadow(p), MemToShadow(p + size));
+}
+
 void ReadContextStack(void *context, uptr *stack, uptr *ssize) {
   UNIMPLEMENTED();
 }
diff --git a/compiler-rt/lib/asan/asan_poisoning.cpp b/compiler-rt/lib/asan/asan_poisoning.cpp
--- a/compiler-rt/lib/asan/asan_poisoning.cpp
+++ b/compiler-rt/lib/asan/asan_poisoning.cpp
@@ -62,12 +62,6 @@
   }
 };
 
-void FlushUnneededASanShadowMemory(uptr p, uptr size) {
-  // Since asan's mapping is compacting, the shadow chunk may be
-  // not page-aligned, so we only flush the page-aligned portion.
-  ReleaseMemoryPagesToOS(MemToShadow(p), MemToShadow(p + size));
-}
-
 void AsanPoisonOrUnpoisonIntraObjectRedzone(uptr ptr, uptr size, bool poison) {
   uptr end = ptr + size;
   if (Verbosity()) {
diff --git a/compiler-rt/lib/asan/asan_rtems.cpp b/compiler-rt/lib/asan/asan_rtems.cpp
--- a/compiler-rt/lib/asan/asan_rtems.cpp
+++ b/compiler-rt/lib/asan/asan_rtems.cpp
@@ -50,6 +50,12 @@
   UNIMPLEMENTED();
 }
 
+void FlushUnneededASanShadowMemory(uptr p, uptr size) {
+  // Since asan's mapping is compacting, the shadow chunk may be
+  // not page-aligned, so we only flush the page-aligned portion.
+  ReleaseMemoryPagesToOS(MemToShadow(p), MemToShadow(p + size));
+}
+
 void AsanCheckDynamicRTPrereqs() {}
 void AsanCheckIncompatibleRT() {}
 void InitializeAsanInterceptors() {}
diff --git a/compiler-rt/lib/asan/asan_win.cpp b/compiler-rt/lib/asan/asan_win.cpp
--- a/compiler-rt/lib/asan/asan_win.cpp
+++ b/compiler-rt/lib/asan/asan_win.cpp
@@ -191,6 +191,12 @@
   UNIMPLEMENTED();
 }
 
+void FlushUnneededASanShadowMemory(uptr p, uptr size) {
+  // Since asan's mapping is compacting, the shadow chunk may be
+  // not page-aligned, so we only flush the page-aligned portion.
+  ReleaseMemoryPagesToOS(MemToShadow(p), MemToShadow(p + size));
+}
+
 // ---------------------- TSD ---------------- {{{
 static bool tsd_key_inited = false;