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authorRussell King <rmk+kernel@arm.linux.org.uk>2014-01-13 23:34:56 +0000
committerRussell King <rmk+kernel@arm.linux.org.uk>2014-01-13 23:34:56 +0000
commit23f6620a360dfd17ac9abbf28e944a9677504819 (patch)
tree889f1d68d9a9a7e3e2f6de007d410fdecca93a54 /arch/arm/include
parentd6e0a2dd12f4067a5bcefb8bbd8ddbeff800afbc (diff)
downloadblackbird-obmc-linux-23f6620a360dfd17ac9abbf28e944a9677504819.tar.gz
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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>
Diffstat (limited to 'arch/arm/include')
-rw-r--r--arch/arm/include/asm/bitops.h54
1 files changed, 44 insertions, 10 deletions
diff --git a/arch/arm/include/asm/bitops.h b/arch/arm/include/asm/bitops.h
index e691ec91e4d3..b2e298a90d76 100644
--- a/arch/arm/include/asm/bitops.h
+++ b/arch/arm/include/asm/bitops.h
@@ -254,25 +254,59 @@ static inline int constant_fls(int x)
}
/*
- * 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 unsigned int __clz(unsigned int x)
+{
+ unsigned int ret;
+
+ asm("clz\t%0, %1" : "=r" (ret) : "r" (x));
+ return ret;
+}
+
+/*
+ * 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)
{
- int ret;
-
if (__builtin_constant_p(x))
return constant_fls(x);
- asm("clz\t%0, %1" : "=r" (ret) : "r" (x));
- ret = 32 - ret;
- return ret;
+ 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 __fls(x) (fls(x) - 1)
-#define ffs(x) ({ unsigned long __t = (x); fls(__t & -__t); })
-#define __ffs(x) (ffs(x) - 1)
#define ffz(x) __ffs( ~(x) )
#endif
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