在 2016年03月28日 10:43, David Miller 写道:
From: "zhaoxiu.zeng" <zhaoxiu.zeng@xxxxxxxxx>
Date: Sun, 27 Mar 2016 14:43:10 +0800
+
+/*
+ * parityN: returns the parity of a N-bit word,
+ * i.e. the number of 1-bits in x modulo 2.
+ */
+
+#define __arch_parity4(w) (__arch_hweight8((w) & 0xf) & 1)
+#define __arch_parity8(w) (__arch_hweight8(w) & 1)
+#define __arch_parity16(w) (__arch_hweight16(w) & 1)
+#define __arch_parity32(w) (__arch_hweight32(w) & 1)
+#define __arch_parity64(w) ((unsigned int)__arch_hweight64(w) & 1)
This looks like asm-generic/ material to me.
This is generic for the architectures which have popcount instruction,
but more higher costs than asm-generic/ for others.
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