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Date: Fri, 15 Apr 2016 23:20:45 +0800
From: zengzhaoxiu@....com
To: linux-kernel@...r.kernel.org
Cc: Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>,
Steven Miao <realmz6@...il.com>,
adi-buildroot-devel@...ts.sourceforge.net
Subject: [PATCH V3] blackfin: optimize ffz, __ffs, ffs, __fls, and fls functions
From: Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>
blackfin has popcount instruction (ONES), we can do the efficient
computing (ffz, __ffs, ffs, __fls, and fls) use this instruction.
Adapted from "https://en.wikipedia.org/wiki/Find_first_set" and
arch/ia64/include/asm/bitops.h.
Changes to V2:
- Fix build errors
Changes to V1:
- Use hweight32 instead __arch_hweight32
Signed-off-by: Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>
---
arch/blackfin/include/asm/bitops.h | 144 ++++++++++++++++++++++++++-----------
1 file changed, 104 insertions(+), 40 deletions(-)
diff --git a/arch/blackfin/include/asm/bitops.h b/arch/blackfin/include/asm/bitops.h
index b298b65..8380d1b 100644
--- a/arch/blackfin/include/asm/bitops.h
+++ b/arch/blackfin/include/asm/bitops.h
@@ -9,20 +9,115 @@
#include <linux/compiler.h>
-#include <asm-generic/bitops/__ffs.h>
-#include <asm-generic/bitops/ffz.h>
-#include <asm-generic/bitops/fls.h>
-#include <asm-generic/bitops/__fls.h>
-#include <asm-generic/bitops/fls64.h>
-#include <asm-generic/bitops/find.h>
-
#ifndef _LINUX_BITOPS_H
#error only <linux/bitops.h> can be included directly
#endif
-#include <asm-generic/bitops/sched.h>
-#include <asm-generic/bitops/ffs.h>
+/*
+ * hweightN: returns the hamming weight (i.e. the number
+ * of bits set) of a N-bit word
+ */
+
+static inline unsigned int __arch_hweight32(unsigned int w)
+{
+ unsigned int res;
+
+ __asm__ ("%0.l = ONES %1;"
+ "%0 = %0.l (Z);"
+ : "=d" (res) : "d" (w));
+ return res;
+}
+
+static inline unsigned int __arch_hweight64(__u64 w)
+{
+ return __arch_hweight32((unsigned int)(w >> 32)) +
+ __arch_hweight32((unsigned int)w);
+}
+
+static inline unsigned int __arch_hweight16(unsigned int w)
+{
+ return __arch_hweight32(w & 0xffff);
+}
+
+static inline unsigned int __arch_hweight8(unsigned int w)
+{
+ return __arch_hweight32(w & 0xff);
+}
+
#include <asm-generic/bitops/const_hweight.h>
+
+/**
+ * ffz - find the first zero bit in a long word
+ * @x: The long word to find the bit in
+ *
+ * Returns the bit-number (0..31) of the first (least significant) zero bit.
+ * Undefined if no zero exists, so code should check against ~0UL first...
+ */
+static inline unsigned long ffz(unsigned long x)
+{
+ return hweight32(x & (~x - 1));
+}
+
+/**
+ * ffs - find first bit set
+ * @x: the word to search
+ *
+ * This is defined the same way as
+ * the libc and compiler builtin ffs routines, therefore
+ * differs in spirit from the above ffz (man ffs).
+ */
+static inline int ffs(int x)
+{
+ if (!x)
+ return 0;
+ return hweight32(x ^ (x - 1));
+}
+
+/**
+ * __ffs - find first bit in word.
+ * @x: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+static inline unsigned long __ffs(unsigned long x)
+{
+ return hweight32(~x & (x - 1));
+}
+
+/*
+ * Find the last (most significant) bit set. Returns 0 for x==0 and
+ * bits are numbered from 1..32 (e.g., fls(9) == 4).
+ */
+static inline int fls(int x)
+{
+ if (!x)
+ return 0;
+ x |= x >> 1;
+ x |= x >> 2;
+ x |= x >> 4;
+ x |= x >> 8;
+ x |= x >> 16;
+ return hweight32(x);
+}
+
+/*
+ * Find the last (most significant) bit set. Undefined for x==0.
+ * Bits are numbered from 0..31 (e.g., __fls(9) == 3).
+ */
+static inline unsigned long __fls(unsigned long x)
+{
+ x |= x >> 1;
+ x |= x >> 2;
+ x |= x >> 4;
+ x |= x >> 8;
+ x |= x >> 16;
+ return hweight32(x) - 1;
+}
+
+#include <asm-generic/bitops/fls64.h>
+#include <asm-generic/bitops/find.h>
+
+#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/ext2-atomic.h>
@@ -106,35 +201,4 @@ static inline int test_and_change_bit(int nr, volatile unsigned long *addr)
/* Needs to be after test_bit and friends */
#include <asm-generic/bitops/le.h>
-/*
- * hweightN: returns the hamming weight (i.e. the number
- * of bits set) of a N-bit word
- */
-
-static inline unsigned int __arch_hweight32(unsigned int w)
-{
- unsigned int res;
-
- __asm__ ("%0.l = ONES %1;"
- "%0 = %0.l (Z);"
- : "=d" (res) : "d" (w));
- return res;
-}
-
-static inline unsigned int __arch_hweight64(__u64 w)
-{
- return __arch_hweight32((unsigned int)(w >> 32)) +
- __arch_hweight32((unsigned int)w);
-}
-
-static inline unsigned int __arch_hweight16(unsigned int w)
-{
- return __arch_hweight32(w & 0xffff);
-}
-
-static inline unsigned int __arch_hweight8(unsigned int w)
-{
- return __arch_hweight32(w & 0xff);
-}
-
#endif /* _BLACKFIN_BITOPS_H */
--
2.5.5
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