[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>
diff --git a/include/asm-i386/bitops.h b/include/asm-i386/bitops.h
index 26eb981..65679ac 100644
--- a/include/asm-i386/bitops.h
+++ b/include/asm-i386/bitops.h
@@ -367,11 +367,6 @@
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 @@
}
/**
+ * 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
*