diff --git a/compiler-rt/lib/scudo/standalone/atomic_helpers.h b/compiler-rt/lib/scudo/standalone/atomic_helpers.h
--- a/compiler-rt/lib/scudo/standalone/atomic_helpers.h
+++ b/compiler-rt/lib/scudo/standalone/atomic_helpers.h
@@ -120,6 +120,14 @@
                                    __ATOMIC_RELAXED);
 }
 
+template <typename T>
+inline bool atomic_compare_exchange_weak(volatile T *A, typename T::Type *Cmp,
+                                         typename T::Type Xchg,
+                                         memory_order MO) {
+  return __atomic_compare_exchange(&A->ValDoNotUse, Cmp, &Xchg, true, MO,
+                                   __ATOMIC_RELAXED);
+}
+
 // Clutter-reducing helpers.
 
 template <typename T>
diff --git a/compiler-rt/lib/scudo/standalone/tests/atomic_test.cpp b/compiler-rt/lib/scudo/standalone/tests/atomic_test.cpp
--- a/compiler-rt/lib/scudo/standalone/tests/atomic_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/atomic_test.cpp
@@ -88,6 +88,16 @@
   EXPECT_FALSE(atomic_compare_exchange_strong(
       reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed));
   EXPECT_EQ(NewVal, OldVal);
+
+  OldVal = 42;
+  NewVal = 24;
+  V = OldVal;
+
+  EXPECT_TRUE(atomic_compare_exchange_weak(reinterpret_cast<T *>(&V), &OldVal,
+                                           NewVal, memory_order_relaxed));
+  EXPECT_FALSE(atomic_compare_exchange_weak(reinterpret_cast<T *>(&V), &OldVal,
+                                            NewVal, memory_order_relaxed));
+  EXPECT_EQ(NewVal, OldVal);
 }
 
 TEST(ScudoAtomicTest, AtomicCompareExchangeTest) {