Use single instruction for find largest set bit on x86_64.
Signed-off-by: Stephen Hemminger <[email protected]>
--- orig/include/asm-x86_64/bitops.h
+++ new/include/asm-x86_64/bitops.h
@@ -370,6 +370,22 @@ 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"
+ "cmovzl %2,%0"
+ : "=r" (r) : "rm" (x), "r" (-1));
+ return r+1;
+}
+
+/**
* hweightN - returns the hamming weight of a N-bit word
* @x: the word to weigh
*
@@ -407,9 +423,6 @@ static __inline__ int ffs(int x)
#define minix_find_first_zero_bit(addr,size) \
find_first_zero_bit((void*)addr,size)
-/* find last set bit */
-#define fls(x) generic_fls(x)
-
#endif /* __KERNEL__ */
#endif /* _X86_64_BITOPS_H */
-
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