MDEV-26720: optimize rw_lock for IA-32, AMD64

storage/innobase/include/rw_lock.h

@@ -38,7 +38,17 @@ class rw_lock
 
   /** Start waiting for an exclusive lock. */
   void write_lock_wait_start()
-  { lock.fetch_or(WRITER_WAITING, std::memory_order_relaxed); }
+  {
+#if defined __GNUC__ && (defined __i386__ || defined __x86_64__)
+    static_assert(WRITER_WAITING == 1U << 30, "compatibility");
+    __asm__ __volatile__("lock btsl $30, %0" : "+m" (lock));
+#elif defined _MSC_VER && (defined _M_IX86 || defined _M_IX64)
+    static_assert(WRITER_WAITING == 1U << 30, "compatibility");
+    _interlockedbittestandset(reinterpret_cast<volatile long*>(&lock), 30);
+#else
+    lock.fetch_or(WRITER_WAITING, std::memory_order_relaxed);
+#endif
+  }
   /** Try to acquire a shared lock.
   @param l the value of the lock word
   @return whether the lock was acquired */