[PATCH v2 1/4] bitmap: introduce bitmap_weighted_xor()

[Yury Norov]

The function helps to XOR bitmaps and calculate Hamming weight of
the result in one pass.

Signed-off-by: Yury Norov <ynorov@xxxxxxxxxx>
---
 include/linux/bitmap.h | 15 +++++++++++++++
 lib/bitmap.c           |  7 +++++++
 2 files changed, 22 insertions(+)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index b0395e4ccf90..874f744870ef 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -46,6 +46,7 @@ struct device;
  *  bitmap_and(dst, src1, src2, nbits)          *dst = *src1 & *src2
  *  bitmap_or(dst, src1, src2, nbits)           *dst = *src1 | *src2
  *  bitmap_weighted_or(dst, src1, src2, nbits)	*dst = *src1 | *src2. Returns Hamming Weight of dst
+ *  bitmap_weighted_xor(dst, src1, src2, nbits)	*dst = *src1 ^ *src2. Returns Hamming Weight of dst
  *  bitmap_xor(dst, src1, src2, nbits)          *dst = *src1 ^ *src2
  *  bitmap_andnot(dst, src1, src2, nbits)       *dst = *src1 & ~(*src2)
  *  bitmap_complement(dst, src, nbits)          *dst = ~(*src)
@@ -168,6 +169,8 @@ void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
 		 const unsigned long *bitmap2, unsigned int nbits);
 unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitmap1,
 				  const unsigned long *bitmap2, unsigned int nbits);
+unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1,
+				  const unsigned long *bitmap2, unsigned int nbits);
 void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
 		  const unsigned long *bitmap2, unsigned int nbits);
 bool __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
@@ -352,6 +355,18 @@ unsigned int bitmap_weighted_or(unsigned long *dst, const unsigned long *src1,
 	}
 }
 
+static __always_inline
+unsigned int bitmap_weighted_xor(unsigned long *dst, const unsigned long *src1,
+				const unsigned long *src2, unsigned int nbits)
+{
+	if (small_const_nbits(nbits)) {
+		*dst = *src1 ^ *src2;
+		return hweight_long(*dst & BITMAP_LAST_WORD_MASK(nbits));
+	} else {
+		return __bitmap_weighted_xor(dst, src1, src2, nbits);
+	}
+}
+
 static __always_inline
 void bitmap_xor(unsigned long *dst, const unsigned long *src1,
 		const unsigned long *src2, unsigned int nbits)
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 9dc526507875..a2bcb5b1fe99 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -361,6 +361,13 @@ unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitma
 	return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] | bitmap2[idx]; dst[idx]; }), bits);
 }
 
+unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1,
+				  const unsigned long *bitmap2, unsigned int bits)
+{
+	return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] ^ bitmap2[idx]; dst[idx]; }), bits);
+}
+EXPORT_SYMBOL(__bitmap_weighted_xor);
+
 void __bitmap_set(unsigned long *map, unsigned int start, int len)
 {
 	unsigned long *p = map + BIT_WORD(start);
-- 
2.43.0