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authorAlexander van Heukelum <heukelum@mailshack.com>2008-03-15 18:30:57 +0100
committerIngo Molnar <mingo@elte.hu>2008-04-26 19:21:16 +0200
commit7d9dff22e8ad06ad330968c9e3d3a2fb55a5f9c3 (patch)
tree1c65cd4cdf14f42d59e72514991c4b04278db8d5
parent12d9c8420b9daa1da3d9e090640fb24bcd0deba2 (diff)
generic: introduce a generic __fls implementation
Add a generic __fls implementation in the same spirit as the generic __ffs one. It finds the last (most significant) set bit in the given long value. Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--include/asm-generic/bitops/__fls.h43
1 files changed, 43 insertions, 0 deletions
diff --git a/include/asm-generic/bitops/__fls.h b/include/asm-generic/bitops/__fls.h
new file mode 100644
index 00000000000..be24465403d
--- /dev/null
+++ b/include/asm-generic/bitops/__fls.h
@@ -0,0 +1,43 @@
+#ifndef _ASM_GENERIC_BITOPS___FLS_H_
+#define _ASM_GENERIC_BITOPS___FLS_H_
+
+#include <asm/types.h>
+
+/**
+ * __fls - find last (most-significant) set bit in a long word
+ * @word: the word to search
+ *
+ * Undefined if no set bit exists, so code should check against 0 first.
+ */
+static inline unsigned long __fls(unsigned long word)
+{
+ int num = BITS_PER_LONG - 1;
+
+#if BITS_PER_LONG == 64
+ if (!(word & (~0ul << 32))) {
+ num -= 32;
+ word <<= 32;
+ }
+#endif
+ if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
+ num -= 16;
+ word <<= 16;
+ }
+ if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
+ num -= 8;
+ word <<= 8;
+ }
+ if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
+ num -= 4;
+ word <<= 4;
+ }
+ if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
+ num -= 2;
+ word <<= 2;
+ }
+ if (!(word & (~0ul << (BITS_PER_LONG-1))))
+ num -= 1;
+ return num;
+}
+
+#endif /* _ASM_GENERIC_BITOPS___FLS_H_ */