[PATCH v2 03/18] bitops: Add parity16(), parity32(), and parity64() helpers

Kuan-Wei Chiu
2025-03-01T14:25:47Z

Introduce parity16(), parity32(), and parity64() functions for
computing parity on 16-bit, 32-bit, and 64-bit integers, respectively.
These functions use __builtin_parity() or __builtin_parityll() when
available, ensuring efficient computation. If the input is a
compile-time constant, they expand using the _parity_const() macro to
allow constant folding.

These additions provide parity computation helpers for larger integer
types, ensuring consistency and performance across different
bit-widths.

Co-developed-by: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com>
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
---
include/linux/bitops.h | 63 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 63 insertions(+)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 4c307d9c1545..41e9e7fb894b 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -276,6 +276,69 @@ static inline __attribute_const__ int parity8(u8 val)
return __builtin_constant_p(val) ? _parity_const(val) : _parity8(val);
}

+#ifndef _parity16
+static inline __attribute_const__ int _parity16(u16 val)
+{
+ return __builtin_parity(val);
+}
+#endif
+
+/**
+ * parity16 - get the parity of an u16 value
+ * @value: the value to be examined
+ *
+ * Determine the parity of the u16 argument.
+ *
+ * Returns:
+ * 0 for even parity, 1 for odd parity
+ */
+static inline __attribute_const__ int parity16(u16 val)
+{
+ return __builtin_constant_p(val) ? _parity_const(val) : _parity16(val);
+}
+
+#ifndef _parity32
+static inline __attribute_const__ int _parity32(u32 val)
+{
+ return __builtin_parity(val);
+}
+#endif
+
+/**
+ * parity32 - get the parity of an u32 value
+ * @value: the value to be examined
+ *
+ * Determine the parity of the u32 argument.
+ *
+ * Returns:
+ * 0 for even parity, 1 for odd parity
+ */
+static inline __attribute_const__ int parity32(u32 val)
+{
+ return __builtin_constant_p(val) ? _parity_const(val) : _parity32(val);
+}
+
+#ifndef _parity64
+static inline __attribute_const__ int _parity64(u64 val)
+{
+ return __builtin_parityll(val);
+}
+#endif
+
+/**
+ * parity64 - get the parity of an u64 value
+ * @value: the value to be examined
+ *
+ * Determine the parity of the u64 argument.
+ *
+ * Returns:
+ * 0 for even parity, 1 for odd parity
+ */
+static inline __attribute_const__ int parity64(u64 val)
+{
+ return __builtin_constant_p(val) ? _parity_const(val) : _parity64(val);
+}
+
/**
* __ffs64 - find first set bit in a 64 bit word
* @word: The 64 bit word
--
2.34.1