[PATCH 13/14] tools: sync lib/find_bit implementation

Yury Norov
2021-02-18T04:12:07Z

Add fast paths to find_*_bit() functions as per kernel implementation.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
tools/include/asm-generic/bitops/find.h | 58 +++++++++++++++++++++++--
tools/lib/find_bit.c | 4 +-
2 files changed, 57 insertions(+), 5 deletions(-)

diff --git a/tools/include/asm-generic/bitops/find.h b/tools/include/asm-generic/bitops/find.h
index 9fe62d10b084..382cd80c61aa 100644
--- a/tools/include/asm-generic/bitops/find.h
+++ b/tools/include/asm-generic/bitops/find.h
@@ -5,6 +5,9 @@
extern unsigned long _find_next_bit(const unsigned long *addr1,
const unsigned long *addr2, unsigned long nbits,
unsigned long start, unsigned long invert, unsigned long le);
+extern unsigned long _find_first_bit(const unsigned long *addr, unsigned long size);
+extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size);
+extern unsigned long _find_last_bit(const unsigned long *addr, unsigned long size);

#ifndef find_next_bit
/**
@@ -20,6 +23,16 @@ static inline
unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
+ if (SMALL_CONST(size - 1)) {
+ unsigned long val;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = *addr & GENMASK(size - 1, offset);
+ return val ? __ffs(val) : size;
+ }
+
return _find_next_bit(addr, NULL, size, offset, 0UL, 0);
}
#endif
@@ -40,6 +53,16 @@ unsigned long find_next_and_bit(const unsigned long *addr1,
const unsigned long *addr2, unsigned long size,
unsigned long offset)
{
+ if (SMALL_CONST(size - 1)) {
+ unsigned long val;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = *addr1 & *addr2 & GENMASK(size - 1, offset);
+ return val ? __ffs(val) : size;
+ }
+
return _find_next_bit(addr1, addr2, size, offset, 0UL, 0);
}
#endif
@@ -58,6 +81,16 @@ static inline
unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
+ if (SMALL_CONST(size - 1)) {
+ unsigned long val;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = *addr | ~GENMASK(size - 1, offset);
+ return val == ~0UL ? size : ffz(val);
+ }
+
return _find_next_bit(addr, NULL, size, offset, ~0UL, 0);
}
#endif
@@ -72,8 +105,17 @@ unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
* Returns the bit number of the first set bit.
* If no bits are set, returns @size.
*/
-extern unsigned long find_first_bit(const unsigned long *addr,
- unsigned long size);
+static inline
+unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
+{
+ if (SMALL_CONST(size - 1)) {
+ unsigned long val = *addr & BITS_FIRST(size - 1);
+
+ return val ? __ffs(val) : size;
+ }
+
+ return _find_first_bit(addr, size);
+}

#endif /* find_first_bit */

@@ -87,7 +129,17 @@ extern unsigned long find_first_bit(const unsigned long *addr,
* Returns the bit number of the first cleared bit.
* If no bits are zero, returns @size.
*/
-unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size);
+static inline
+unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
+{
+ if (SMALL_CONST(size - 1)) {
+ unsigned long val = *addr | ~BITS_FIRST(size - 1);
+
+ return val == ~0UL ? size : ffz(val);
+ }
+
+ return _find_first_zero_bit(addr, size);
+}
#endif

#endif /*_TOOLS_LINUX_ASM_GENERIC_BITOPS_FIND_H_ */
diff --git a/tools/lib/find_bit.c b/tools/lib/find_bit.c
index c3378b291205..a77884ca30ec 100644
--- a/tools/lib/find_bit.c
+++ b/tools/lib/find_bit.c
@@ -83,7 +83,7 @@ unsigned long _find_next_bit(const unsigned long *addr1,
/*
* Find the first set bit in a memory region.
*/
-unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
+unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
{
unsigned long idx;

@@ -100,7 +100,7 @@ unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
/*
* Find the first cleared bit in a memory region.
*/
-unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
+unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
{
unsigned long idx;

--
2.25.1