[PATCH v5 05/23] xen/asm-generic: introduce generic find first set bit functions

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

These functions can be useful for architectures that don't
have corresponding arch-specific instructions.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
 Changes in V5:
   - new patch
---
 xen/include/asm-generic/bitops/__ffs.h        | 47 +++++++++++++++++++
 xen/include/asm-generic/bitops/ffs.h          |  9 ++++
 xen/include/asm-generic/bitops/ffsl.h         | 16 +++++++
 .../asm-generic/bitops/find-first-set-bit.h   | 17 +++++++
 4 files changed, 89 insertions(+)
 create mode 100644 xen/include/asm-generic/bitops/__ffs.h
 create mode 100644 xen/include/asm-generic/bitops/ffs.h
 create mode 100644 xen/include/asm-generic/bitops/ffsl.h
 create mode 100644 xen/include/asm-generic/bitops/find-first-set-bit.h

diff --git a/xen/include/asm-generic/bitops/__ffs.h 
b/xen/include/asm-generic/bitops/__ffs.h
new file mode 100644
index 0000000000..fecb4484d9
--- /dev/null
+++ b/xen/include/asm-generic/bitops/__ffs.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_BITOPS___FFS_H_
+#define _ASM_GENERIC_BITOPS___FFS_H_
+
+/**
+ * ffs - find first bit in word.
+ * @word: The word to search
+ *
+ * Returns 0 if no bit exists, otherwise returns 1-indexed bit location.
+ */
+static inline unsigned int __ffs(unsigned long word)
+{
+    unsigned int num = 0;
+
+#if BITS_PER_LONG == 64
+    if ( (word & 0xffffffff) == 0 )
+    {
+        num += 32;
+        word >>= 32;
+    }
+#endif
+    if ( (word & 0xffff) == 0 )
+    {
+        num += 16;
+        word >>= 16;
+    }
+    if ( (word & 0xff) == 0 )
+    {
+        num += 8;
+        word >>= 8;
+    }
+    if ( (word & 0xf) == 0 )
+    {
+        num += 4;
+        word >>= 4;
+    }
+    if ( (word & 0x3) == 0 )
+    {
+        num += 2;
+        word >>= 2;
+    }
+    if ( (word & 0x1) == 0 )
+        num += 1;
+    return num;
+}
+
+#endif /* _ASM_GENERIC_BITOPS___FFS_H_ */
diff --git a/xen/include/asm-generic/bitops/ffs.h 
b/xen/include/asm-generic/bitops/ffs.h
new file mode 100644
index 0000000000..3f75fded14
--- /dev/null
+++ b/xen/include/asm-generic/bitops/ffs.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_BITOPS_FFS_H_
+#define _ASM_GENERIC_BITOPS_FFS_H_
+
+#include <xen/macros.h>
+
+#define ffs(x) ({ unsigned int t_ = (x); fls(ISOLATE_LSB(t_)); })
+
+#endif /* _ASM_GENERIC_BITOPS_FFS_H_ */
diff --git a/xen/include/asm-generic/bitops/ffsl.h 
b/xen/include/asm-generic/bitops/ffsl.h
new file mode 100644
index 0000000000..d0996808f5
--- /dev/null
+++ b/xen/include/asm-generic/bitops/ffsl.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_BITOPS_FFSL_H_
+#define _ASM_GENERIC_BITOPS_FFSL_H_
+
+/**
+ * ffsl - find first bit in long.
+ * @word: The word to search
+ *
+ * Returns 0 if no bit exists, otherwise returns 1-indexed bit location.
+ */
+static inline unsigned int ffsl(unsigned long word)
+{
+    return generic_ffsl(word);
+}
+
+#endif /* _ASM_GENERIC_BITOPS_FFSL_H_ */
diff --git a/xen/include/asm-generic/bitops/find-first-set-bit.h 
b/xen/include/asm-generic/bitops/find-first-set-bit.h
new file mode 100644
index 0000000000..7d28b8a89b
--- /dev/null
+++ b/xen/include/asm-generic/bitops/find-first-set-bit.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_BITOPS_FIND_FIRST_SET_BIT_H_
+#define _ASM_GENERIC_BITOPS_FIND_FIRST_SET_BIT_H_
+
+/**
+ * find_first_set_bit - find the first set bit in @word
+ * @word: the word to search
+ *
+ * Returns the bit-number of the first set bit (first bit being 0).
+ * The input must *not* be zero.
+ */
+static inline unsigned int find_first_set_bit(unsigned long word)
+{
+        return ffsl(word) - 1;
+}
+
+#endif /* _ASM_GENERIC_BITOPS_FIND_FIRST_SET_BIT_H_ */
-- 
2.43.0