[PATCH] LOG2: Provide ilog2() fallbacks for powerpc

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

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 20 insertions, 1 deletions

diff --git a/include/asm-powerpc/bitops.h b/include/asm-powerpc/bitops.h
index c341063d0804..0288144ea024 100644
--- a/include/asm-powerpc/bitops.h
+++ b/include/asm-powerpc/bitops.h
@@ -190,7 +190,8 @@ static __inline__ void set_bits(unsigned long mask, unsigned long *addr)
  * 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 +199,24 @@ static __inline__ int __ilog2(unsigned long x)
         return BITS_PER_LONG - 1 - lz;
 }
 
+static inline __attribute__((const))
+int __ilog2_u32(u32 n)
+{
+        int bit;
+        asm ("cntlzw %0,%1" : "=r" (bit) : "r" (n));
+        return 31 - bit;
+}
+
+#ifdef __powerpc64__
+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