Oilpan: Fix ASan instrumentation around heap object headers.

Source/wtf/Atomics.h

Index: Source/wtf/Atomics.h
diff --git a/Source/wtf/Atomics.h b/Source/wtf/Atomics.h
index aaad9c9e90cbe954fd9d30ec7a89488822201298..df9e9750eb5d42035c2ef484a573c6774221195a 100644
--- a/Source/wtf/Atomics.h
+++ b/Source/wtf/Atomics.h
@@ -43,6 +43,10 @@
 #include <sanitizer/tsan_interface_atomic.h>
 #endif
 
+#if defined(ADDRESS_SANITIZER)
+#include <sanitizer/asan_interface.h>
+#endif
+
 namespace WTF {
 
 #if COMPILER(MSVC)
@@ -106,6 +110,7 @@ ALWAYS_INLINE void atomicSetOneToZero(int volatile* ptr)
 #endif
 
 #if defined(THREAD_SANITIZER)
+
 ALWAYS_INLINE void releaseStore(volatile int* ptr, int value)
 {
     __tsan_atomic32_store(ptr, value, __tsan_memory_order_release);
@@ -125,6 +130,7 @@ ALWAYS_INLINE unsigned acquireLoad(volatile const unsigned* ptr)
 {
     return static_cast<unsigned>(__tsan_atomic32_load(reinterpret_cast<volatile const int*>(ptr), __tsan_memory_order_acquire));
 }
+
 #else
 
 #if CPU(X86) || CPU(X86_64)
@@ -179,10 +185,41 @@ ALWAYS_INLINE unsigned acquireLoad(volatile const unsigned* ptr)
     return value;
 }
 
+#if defined(ADDRESS_SANITIZER)
+
+__attribute__((no_sanitize_address)) ALWAYS_INLINE void asanUnsafeReleaseStore(volatile unsigned* ptr, unsigned value)
+{
+    MEMORY_BARRIER();
+    *ptr = value;
+}
+
+__attribute__((no_sanitize_address)) ALWAYS_INLINE unsigned asanUnsafeAcquireLoad(volatile const unsigned* ptr)
+{
+    unsigned value = *ptr;
+    MEMORY_BARRIER();
+    return value;
+}
+
+#endif // defined(ADDRESS_SANITIZER)
+
 #undef MEMORY_BARRIER
 
 #endif
 
+#if !defined(ADDRESS_SANITIZER)
+
+ALWAYS_INLINE void asanUnsafeReleaseStore(volatile unsigned* ptr, unsigned value)
+{
+    releaseStore(ptr, value);
+}
+
+ALWAYS_INLINE unsigned asanUnsafeAcquireLoad(volatile const unsigned* ptr)
+{
+    return acquireLoad(ptr);
+}
+
+#endif
+
 } // namespace WTF
 
 using WTF::atomicAdd;
@@ -194,4 +231,10 @@ using WTF::atomicSetOneToZero;
 using WTF::acquireLoad;
 using WTF::releaseStore;
 
+// These methods allow loading from and storing to poisoned memory. Only
+// use these methods if you know what you are doing since they will
+// silence use-after-poison errors from ASan.
+using WTF::asanUnsafeAcquireLoad;
+using WTF::asanUnsafeReleaseStore;
+
 #endif // Atomics_h