diff --git a/arch/generic/include/bfdev/asm/dword.h b/arch/generic/include/bfdev/asm/dword.h
new file mode 100644
index 00000000..4a45aa82
--- /dev/null
+++ b/arch/generic/include/bfdev/asm/dword.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * Copyright(c) 2024 John Sanpe <sanpeqf@gmail.com>
+ */
+
+#ifndef _BFDEV_ASM_DWORD_H_
+#define _BFDEV_ASM_DWORD_H_
+
+#include <bfdev/config.h>
+#include <bfdev/asm/bitsperlong.h>
+
+BFDEV_BEGIN_DECLS
+
+#if BFDEV_BITS_PER_LONG == 32
+# define __BFDEV_ASM_HAVE_DWORD 1
+#else /* BFDEV_BITS_PER_LONG == 64 */
+# define __BFDEV_ASM_HAVE_DWORD __SIZEOF_INT128__
+#endif
+
+#ifndef BFDEV_ASM_HAVE_DWORD
+# define BFDEV_ASM_HAVE_DWORD __BFDEV_ASM_HAVE_DWORD
+#endif
+
+BFDEV_END_DECLS
+
+#ifdef BFDEV_ASM_HAVE_DWORD
+# include <bfdev/asm-generic/dword-compiler.h>
+#endif
+
+#include <bfdev/asm-generic/dword.h>
+
+#endif /* _BFDEV_ASM_DWORD_H_ */
diff --git a/include/bfdev/asm-generic/dword-compiler.h b/include/bfdev/asm-generic/dword-compiler.h
new file mode 100644
index 00000000..31961603
--- /dev/null
+++ b/include/bfdev/asm-generic/dword-compiler.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * Copyright(c) 2025 John Sanpe <sanpeqf@gmail.com>
+ */
+
+#ifndef _BFDEV_ASM_GENERIC_DWORD_H_
+#define _BFDEV_ASM_GENERIC_DWORD_H_
+
+#include <bfdev/config.h>
+#include <bfdev/types.h>
+#include <bfdev/stddef.h>
+#include <bfdev/bits.h>
+
+BFDEV_BEGIN_DECLS
+
+#if BFDEV_BITS_PER_LONG == 32
+typedef uint64_t bfdev_dword_t;
+#else
+typedef unsigned __int128 bfdev_dword_t;
+#endif
+
+#ifndef bfdev_dword_addd
+# define bfdev_dword_addd bfdev_dword_addd
+static __bfdev_always_inline void
+bfdev_dword_addd(bfdev_uw_t *sh, bfdev_uw_t *sl, bfdev_uw_t ah,
+                 bfdev_uw_t al, bfdev_uw_t bh, bfdev_uw_t bl)
+{
+    bfdev_dword_t ac, bc, sc;
+
+    ac = (bfdev_dword_t)ah << BFDEV_BITS_PER_LONG | al;
+    bc = (bfdev_dword_t)bh << BFDEV_BITS_PER_LONG | bl;
+
+    sc = ac + bc;
+    *sh = (bfdev_uw_t)(sc >> BFDEV_BITS_PER_LONG);
+    *sl = (bfdev_uw_t)sc;
+}
+#endif
+
+#ifndef bfdev_dword_sub_ddmmss
+# define bfdev_dword_sub_ddmmss bfdev_dword_sub_ddmmss
+static __bfdev_always_inline void
+bfdev_dword_sub_ddmmss(bfdev_uw_t *sh, bfdev_uw_t *sl, bfdev_uw_t ah,
+                       bfdev_uw_t al, bfdev_uw_t bh, bfdev_uw_t bl)
+{
+    bfdev_dword_t ac, bc, sc;
+
+    ac = (bfdev_dword_t)ah << BFDEV_BITS_PER_LONG | al;
+    bc = (bfdev_dword_t)bh << BFDEV_BITS_PER_LONG | bl;
+
+    sc = ac - bc;
+    *sh = (bfdev_uw_t)(sc >> BFDEV_BITS_PER_LONG);
+    *sl = (bfdev_uw_t)sc;
+}
+#endif
+
+#ifndef bfdev_dword_umul_ppmm
+# define bfdev_dword_umul_ppmm bfdev_dword_umul_ppmm
+static __bfdev_always_inline void
+bfdev_dword_umul_ppmm(bfdev_uw_t *dh, bfdev_uw_t *dl,
+                      bfdev_uw_t va, bfdev_uw_t vb)
+{
+    bfdev_dword_t sc;
+
+    sc = (bfdev_dword_t)va * vb;
+    *dh = (bfdev_uw_t)(sc >> BFDEV_BITS_PER_LONG);
+    *dl = (bfdev_uw_t)sc;
+}
+#endif
+
+#ifndef bfdev_dword_udiv_qrnnd
+# define bfdev_dword_udiv_qrnnd bfdev_dword_udiv_qrnnd
+static __bfdev_always_inline void
+bfdev_dword_udiv_qrnnd(bfdev_uw_t *quot, bfdev_uw_t *rem, bfdev_uw_t vh,
+                       bfdev_uw_t vl, bfdev_uw_t div)
+{
+    bfdev_dword_t vc;
+
+    vc = (bfdev_dword_t)vh << BFDEV_BITS_PER_LONG | vl;
+    *quot = (bfdev_uw_t)(vc / div);
+    *rem = (bfdev_uw_t)(vc % div);
+}
+#endif
+
+BFDEV_END_DECLS
+
+#endif /* _BFDEV_ASM_GENERIC_DWORD_H_ */