linux-kernel - [PATCH 7/7] Provide ilog2() fallbacks for powerpc [try #2]

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Message-Id: <20060913175947.21216.12478.stgit@warthog.cambridge.redhat.com>
Date:	Wed, 13 Sep 2006 18:59:47 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...l.org
Cc:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	dhowells@...hat.com
Subject: [PATCH 7/7] Provide ilog2() fallbacks for powerpc [try #2]

From: David Howells <dhowells@...hat.com>

Provide ilog2() fallbacks for powerpc for 32-bit numbers and 64-bit numbers on
ppc64.

Signed-Off-By: David Howells <dhowells@...hat.com>
---

 include/asm-powerpc/bitops.h |   23 ++++++++++++++++++++++-
 1 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/include/asm-powerpc/bitops.h b/include/asm-powerpc/bitops.h
index c341063..b6b1169 100644
--- a/include/asm-powerpc/bitops.h
+++ b/include/asm-powerpc/bitops.h
@@ -190,7 +190,8 @@ #include <asm-generic/bitops/non-atomic.
  * Return the zero-based bit position (LE, not IBM bit numbering) of
  * the most significant 1-bit in a double word.
  */
-static __inline__ int __ilog2(unsigned long x)
+static __inline__ __attribute__((const))
+int __ilog2(unsigned long x)
 {
 	int lz;
 
@@ -198,6 +199,26 @@ static __inline__ int __ilog2(unsigned l
 	return BITS_PER_LONG - 1 - lz;
 }
 
+#define ARCH_HAS_ILOG2_U32
+static inline __attribute__((const))
+int __ilog2_u32(u32 n)
+{
+	int bit;
+	asm ("cntlzw %0,%1" : "=r" (bit) : "r" (n));
+	return 31 - bit;
+}
+
+#ifdef __powerpc64__
+#define ARCH_HAS_ILOG2_U64
+static inline __attribute__((const))
+int __ilog2_u64(u32 n)
+{
+	int bit;
+	asm ("cntlzd %0,%1" : "=r" (bit) : "r" (n));
+	return 63 - bit;
+}
+#endif
+
 /*
  * Determines the bit position of the least significant 0 bit in the
  * specified double word. The returned bit position will be
-
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