[PATCH] FRV: Optimise ffs()
Optimise ffs(x) by using fls(x & x - 1) which we optimise to use the SCAN
instruction.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-frv/bitops.h b/include/asm-frv/bitops.h
index 591eecc..1f70d47 100644
--- a/include/asm-frv/bitops.h
+++ b/include/asm-frv/bitops.h
@@ -157,8 +157,6 @@
__constant_test_bit((nr),(addr)) : \
__test_bit((nr),(addr)))
-#include <asm-generic/bitops/ffs.h>
-#include <asm-generic/bitops/__ffs.h>
#include <asm-generic/bitops/find.h>
/**
@@ -227,6 +225,37 @@
}
+/**
+ * ffs - find first bit set
+ * @x: the word to search
+ *
+ * - return 32..1 to indicate bit 31..0 most least significant bit set
+ * - return 0 to indicate no bits set
+ */
+static inline __attribute__((const))
+int ffs(int x)
+{
+ /* Note: (x & -x) gives us a mask that is the least significant
+ * (rightmost) 1-bit of the value in x.
+ */
+ return fls(x & -x);
+}
+
+/**
+ * __ffs - find first bit set
+ * @x: the word to search
+ *
+ * - return 31..0 to indicate bit 31..0 most least significant bit set
+ * - if no bits are set in x, the result is undefined
+ */
+static inline __attribute__((const))
+int __ffs(unsigned long x)
+{
+ int bit;
+ asm("scan %1,gr0,%0" : "=r"(bit) : "r"(x & -x));
+ return 31 - bit;
+}
+
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/hweight.h>