netdev - [PATCH net-next] filter: add bpf_optimize

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Message-Id: <1416512551-22252-1-git-send-email-kda@linux-powerpc.org>
Date:	Thu, 20 Nov 2014 22:42:31 +0300
From:	Denis Kirjanov <kda@...ux-powerpc.org>
To:	netdev@...r.kernel.org
Cc:	Denis Kirjanov <kda@...ux-powerpc.org>,
	Alexei Starovoitov <ast@...mgrid.com>
Subject: [PATCH net-next] filter: add bpf_optimize_div()

optimize_div() found in  mips bpf jit is really usefull
for other arches. So let's put it in filter.h

CC: Alexei Starovoitov <ast@...mgrid.com>
Signed-off-by: Denis Kirjanov <kda@...ux-powerpc.org>
---
 include/linux/filter.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index ca95abd..b385637 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -414,6 +414,17 @@ static inline void bpf_jit_dump(unsigned int flen, unsigned int proglen,
 		print_hex_dump(KERN_ERR, "JIT code: ", DUMP_PREFIX_OFFSET,
 			       16, 1, image, proglen, false);
 }
+
+static inline int bpf_optimize_div(u32 *k)
+{
+	/* power of 2 divides can be implemented with right shift */
+	if (!(*k & (*k-1))) {
+		*k = ilog2(*k);
+		return 1;
+	}
+
+	return 0;
+}
 #else
 static inline void bpf_jit_compile(struct bpf_prog *fp)
 {
-- 
2.1.0

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