ARM: fix ffs/fls implementations to match x86
ARMs ffs/fls implementations are not type compatible with x86, so when
they're used in combination with min()/max(), they provoke warnings.
Change these to be inline functions with the correct types, providing
the clz as a separate documentation, and document their individual
behaviours.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/include/asm/bitops.h b/arch/arm/include/asm/bitops.h
index e691ec9..b2e298a 100644
--- a/arch/arm/include/asm/bitops.h
+++ b/arch/arm/include/asm/bitops.h
@@ -254,25 +254,59 @@
}
/*
- * On ARMv5 and above those functions can be implemented around
- * the clz instruction for much better code efficiency.
+ * On ARMv5 and above those functions can be implemented around the
+ * clz instruction for much better code efficiency. __clz returns
+ * the number of leading zeros, zero input will return 32, and
+ * 0x80000000 will return 0.
*/
-
-static inline int fls(int x)
+static inline unsigned int __clz(unsigned int x)
{
- int ret;
-
- if (__builtin_constant_p(x))
- return constant_fls(x);
+ unsigned int ret;
asm("clz\t%0, %1" : "=r" (ret) : "r" (x));
- ret = 32 - ret;
+
return ret;
}
-#define __fls(x) (fls(x) - 1)
-#define ffs(x) ({ unsigned long __t = (x); fls(__t & -__t); })
-#define __ffs(x) (ffs(x) - 1)
+/*
+ * fls() returns zero if the input is zero, otherwise returns the bit
+ * position of the last set bit, where the LSB is 1 and MSB is 32.
+ */
+static inline int fls(int x)
+{
+ if (__builtin_constant_p(x))
+ return constant_fls(x);
+
+ return 32 - __clz(x);
+}
+
+/*
+ * __fls() returns the bit position of the last bit set, where the
+ * LSB is 0 and MSB is 31. Zero input is undefined.
+ */
+static inline unsigned long __fls(unsigned long x)
+{
+ return fls(x) - 1;
+}
+
+/*
+ * ffs() returns zero if the input was zero, otherwise returns the bit
+ * position of the first set bit, where the LSB is 1 and MSB is 32.
+ */
+static inline int ffs(int x)
+{
+ return fls(x & -x);
+}
+
+/*
+ * __ffs() returns the bit position of the first bit set, where the
+ * LSB is 0 and MSB is 31. Zero input is undefined.
+ */
+static inline unsigned long __ffs(unsigned long x)
+{
+ return ffs(x) - 1;
+}
+
#define ffz(x) __ffs( ~(x) )
#endif