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authorStephen Hemminger <shemminger@osdl.org>2006-01-06 00:12:12 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-06 08:33:38 -0800
commitd832245d7cc16d50b29c1b708ccbe9c75ac376a3 (patch)
tree2fc22b6337fc433a6b392e9b008339d8031e8e1c
parente31b88ba49460653bab87423287bb68743f5de5c (diff)
[PATCH] x86: fls() in asm
There is a single instruction on i386 to find largest set bit; so it makes sense to use it (like we use bfs for ffs()). Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--include/asm-i386/bitops.h22
1 files changed, 17 insertions, 5 deletions
diff --git a/include/asm-i386/bitops.h b/include/asm-i386/bitops.h
index 26eb9811712..65679aca4b2 100644
--- a/include/asm-i386/bitops.h
+++ b/include/asm-i386/bitops.h
@@ -367,11 +367,6 @@ static inline unsigned long ffz(unsigned long word)
return word;
}
-/*
- * fls: find last bit set.
- */
-
-#define fls(x) generic_fls(x)
#define fls64(x) generic_fls64(x)
#ifdef __KERNEL__
@@ -415,6 +410,23 @@ static inline int ffs(int x)
}
/**
+ * fls - find last bit set
+ * @x: the word to search
+ *
+ * This is defined the same way as ffs.
+ */
+static inline int fls(int x)
+{
+ int r;
+
+ __asm__("bsrl %1,%0\n\t"
+ "jnz 1f\n\t"
+ "movl $-1,%0\n"
+ "1:" : "=r" (r) : "rm" (x));
+ return r+1;
+}
+
+/**
* hweightN - returns the hamming weight of a N-bit word
* @x: the word to weigh
*