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Date: Wed, 20 Jan 2021 16:06:29 -0800
From: Yury Norov <yury.norov@...il.com>
To: linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org,
linux-sh@...r.kernel.org, linux-arch@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Yoshinori Sato <ysato@...rs.sourceforge.jp>,
Rich Felker <dalias@...c.org>, Arnd Bergmann <arnd@...db.de>,
Dennis Zhou <dennis@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
David Sterba <dsterba@...e.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Stefano Brivio <sbrivio@...hat.com>,
"Ma, Jianpeng" <jianpeng.ma@...el.com>,
Wei Yang <richard.weiyang@...ux.alibaba.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Subject: [PATCH 5/6] lib: add fast path for find_next_*_bit()
Similarly to bitmap functions, find_next_*_bit() users will benefit
if we'll handle a case of bitmaps that fit into a single word. In the
very best case, the compiler may replace a function call with a
single ffs or ffz instruction.
Signed-off-by: Yury Norov <yury.norov@...il.com>
---
include/asm-generic/bitops/find.h | 39 +++++++++++++++++++++++++++++++
include/asm-generic/bitops/le.h | 28 ++++++++++++++++++++++
2 files changed, 67 insertions(+)
diff --git a/include/asm-generic/bitops/find.h b/include/asm-generic/bitops/find.h
index 7ad70dab8e93..d45096069011 100644
--- a/include/asm-generic/bitops/find.h
+++ b/include/asm-generic/bitops/find.h
@@ -20,6 +20,18 @@ static inline
unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
+ if (small_const_nbits(size)) {
+ unsigned long val;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = *addr & BITMAP_FIRST_WORD_MASK(offset)
+ & BITMAP_LAST_WORD_MASK(size);
+
+ return val ? __ffs(val) : size;
+ }
+
return _find_next_bit(addr, NULL, size, offset, 0UL, 0);
}
#endif
@@ -40,6 +52,18 @@ unsigned long find_next_and_bit(const unsigned long *addr1,
const unsigned long *addr2, unsigned long size,
unsigned long offset)
{
+ if (small_const_nbits(size)) {
+ unsigned long val;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = *addr1 & *addr2 & BITMAP_FIRST_WORD_MASK(offset)
+ & BITMAP_LAST_WORD_MASK(size);
+
+ return val ? __ffs(val) : size;
+ }
+
return _find_next_bit(addr1, addr2, size, offset, 0UL, 0);
}
#endif
@@ -58,6 +82,21 @@ static inline
unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
+ if (small_const_nbits(size)) {
+ unsigned long val, idx;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = *addr | ~BITMAP_FIRST_WORD_MASK(offset);
+ if (val == ~0UL)
+ return size;
+
+ idx = ffz(val);
+
+ return idx < size ? idx : size;
+ }
+
return _find_next_bit(addr, NULL, size, offset, ~0UL, 0);
}
#endif
diff --git a/include/asm-generic/bitops/le.h b/include/asm-generic/bitops/le.h
index 4cf44ea16ec0..f4a76d3d145f 100644
--- a/include/asm-generic/bitops/le.h
+++ b/include/asm-generic/bitops/le.h
@@ -5,6 +5,7 @@
#include <asm/types.h>
#include <asm/byteorder.h>
#include <asm-generic/bitops/find.h>
+#include <linux/swab.h>
#if defined(__LITTLE_ENDIAN)
@@ -37,6 +38,21 @@ static inline
unsigned long find_next_zero_bit_le(const void *addr, unsigned
long size, unsigned long offset)
{
+ if (small_const_nbits(size)) {
+ unsigned long val = *(const unsigned long *)addr, idx;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = swab(val) | ~BITMAP_FIRST_WORD_MASK(offset);
+ if (val == ~0UL)
+ return size;
+
+ idx = ffz(val);
+
+ return idx < size ? idx : size;
+ }
+
return _find_next_bit(addr, NULL, size, offset, ~0UL, 1);
}
#endif
@@ -46,6 +62,18 @@ static inline
unsigned long find_next_bit_le(const void *addr, unsigned
long size, unsigned long offset)
{
+ if (small_const_nbits(size)) {
+ unsigned long val = *(const unsigned long *)addr;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = swab(val) & BITMAP_FIRST_WORD_MASK(offset)
+ & BITMAP_LAST_WORD_MASK(size);
+
+ return val ? __ffs(val) : size;
+ }
+
return _find_next_bit(addr, NULL, size, offset, 0UL, 1);
}
#endif
--
2.25.1
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