From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Thu, 25 Feb 2021 12:48:52 +0000 (+0100)
Subject: macro: add hweight*() helpers
X-Git-Tag: lxc-5.0.0~267^2~7
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=265dc73af65742b65ed4bcf025f1e7c5d5fd23b1;p=thirdparty%2Flxc.git

macro: add hweight*() helpers

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---

diff --git a/src/lxc/macro.h b/src/lxc/macro.h
index c98ca5900..a54fe72b3 100644
--- a/src/lxc/macro.h
+++ b/src/lxc/macro.h
@@ -708,4 +708,29 @@ enum {
 		_min1 < _min2 ? _min1 : _min2; \
 	})
 
+#define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
+
+/*
+ * Compile time versions of __arch_hweightN()
+ */
+#define __const_hweight8(w)		\
+	((unsigned int)			\
+	 ((!!((w) & (1ULL << 0))) +	\
+	  (!!((w) & (1ULL << 1))) +	\
+	  (!!((w) & (1ULL << 2))) +	\
+	  (!!((w) & (1ULL << 3))) +	\
+	  (!!((w) & (1ULL << 4))) +	\
+	  (!!((w) & (1ULL << 5))) +	\
+	  (!!((w) & (1ULL << 6))) +	\
+	  (!!((w) & (1ULL << 7)))))
+
+#define __const_hweight16(w) (__const_hweight8(w)  + __const_hweight8((w)  >> 8 ))
+#define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))
+#define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
+
+#define hweight8(w) __const_hweight8(w)
+#define hweight16(w) __const_hweight16(w)
+#define hweight32(w) __const_hweight32(w)
+#define hweight64(w) __const_hweight64(w)
+
 #endif /* __LXC_MACRO_H */