From: Yury Norov <yury.norov@gmail.com>
To: linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org,
linux-sh@vger.kernel.org, linux-arch@vger.kernel.org
Cc: Yury Norov <yury.norov@gmail.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>, Arnd Bergmann <arnd@arndb.de>,
Dennis Zhou <dennis@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Wolfram Sang <wsa+renesas@sang-engineering.com>,
David Sterba <dsterba@suse.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Stefano Brivio <sbrivio@redhat.com>,
"Ma, Jianpeng" <jianpeng.ma@intel.com>,
Wei Yang <richard.weiyang@linux.alibaba.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Subject: [PATCH 5/6] lib: add fast path for find_next_*_bit()
Date: Wed, 20 Jan 2021 16:06:29 -0800 [thread overview]
Message-ID: <20210121000630.371883-6-yury.norov@gmail.com> (raw)
In-Reply-To: <20210121000630.371883-1-yury.norov@gmail.com>
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@gmail.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
next prev parent reply other threads:[~2021-01-21 0:59 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 0:06 [PATCH 0/6] lib/find_bit: fast path for small bitmaps Yury Norov
2021-01-21 0:06 ` [PATCH 1/6] arch: rearrahge headers inclusion order in asm/bitops for m68k and sh Yury Norov
2021-01-21 8:03 ` Geert Uytterhoeven
2021-01-21 8:47 ` John Paul Adrian Glaubitz
2021-01-21 0:06 ` [PATCH 2/6] bitmap: move some macros from linux/bitmap.h to linux/bitops.h Yury Norov
2021-01-21 10:19 ` Andy Shevchenko
2021-01-21 20:38 ` Yury Norov
2021-01-21 0:06 ` [PATCH 3/6] tools: sync bitops macro definitions with the kernel Yury Norov
2021-01-21 10:23 ` Andy Shevchenko
2021-01-21 0:06 ` [PATCH 4/6] lib: inline _find_next_bit() wrappers Yury Norov
2021-01-21 10:28 ` Andy Shevchenko
2021-01-29 6:41 ` Yury Norov
2021-01-21 0:06 ` Yury Norov [this message]
2021-01-21 10:34 ` [PATCH 5/6] lib: add fast path for find_next_*_bit() Andy Shevchenko
2021-01-21 0:06 ` [PATCH 6/6] lib: add fast path for find_first_*_bit() and find_last_bit() Yury Norov
2021-01-21 10:40 ` Andy Shevchenko
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