Inspired find_next_*bit function series, add find_prev_*_bit series.
I'm not sure whether it'll be used right now But, I add these functions
for future usage.
Signed-off-by: Levi Yun <[email protected]>
---
fs/ufs/util.h | 24 +++---
include/asm-generic/bitops/find.h | 69 ++++++++++++++++
include/asm-generic/bitops/le.h | 33 ++++++++
include/linux/bitops.h | 34 +++++---
lib/find_bit.c | 126 +++++++++++++++++++++++++++++-
5 files changed, 260 insertions(+), 26 deletions(-)
diff --git a/fs/ufs/util.h b/fs/ufs/util.h
index 4931bec1a01c..7c87c77d10ca 100644
--- a/fs/ufs/util.h
+++ b/fs/ufs/util.h
@@ -2,7 +2,7 @@
/*
* linux/fs/ufs/util.h
*
- * Copyright (C) 1998
+ * Copyright (C) 1998
* Daniel Pirkl <[email protected]>
* Charles University, Faculty of Mathematics and Physics
*/
@@ -263,7 +263,7 @@ extern int ufs_prepare_chunk(struct page *page,
loff_t pos, unsigned len);
/*
* These functions manipulate ufs buffers
*/
-#define ubh_bread(sb,fragment,size) _ubh_bread_(uspi,sb,fragment,size)
+#define ubh_bread(sb,fragment,size) _ubh_bread_(uspi,sb,fragment,size)
extern struct ufs_buffer_head * _ubh_bread_(struct
ufs_sb_private_info *, struct super_block *, u64 , u64);
extern struct ufs_buffer_head * ubh_bread_uspi(struct
ufs_sb_private_info *, struct super_block *, u64, u64);
extern void ubh_brelse (struct ufs_buffer_head *);
@@ -296,7 +296,7 @@ static inline void *get_usb_offset(struct
ufs_sb_private_info *uspi,
unsigned int offset)
{
unsigned int index;
-
+
index = offset >> uspi->s_fshift;
offset &= ~uspi->s_fmask;
return uspi->s_ubh.bh[index]->b_data + offset;
@@ -411,9 +411,9 @@ static inline unsigned _ubh_find_next_zero_bit_(
offset = 0;
}
return (base << uspi->s_bpfshift) + pos - begin;
-}
+}
-static inline unsigned find_last_zero_bit (unsigned char * bitmap,
+static inline unsigned __ubh_find_last_zero_bit(unsigned char * bitmap,
unsigned size, unsigned offset)
{
unsigned bit, i;
@@ -453,7 +453,7 @@ static inline unsigned _ubh_find_last_zero_bit_(
size + (uspi->s_bpf - start), uspi->s_bpf)
- (uspi->s_bpf - start);
size -= count;
- pos = find_last_zero_bit (ubh->bh[base]->b_data,
+ pos = __ubh_find_last_zero_bit(ubh->bh[base]->b_data,
start, start - count);
if (pos > start - count || !size)
break;
@@ -461,7 +461,7 @@ static inline unsigned _ubh_find_last_zero_bit_(
start = uspi->s_bpf;
}
return (base << uspi->s_bpfshift) + pos - begin;
-}
+}
#define ubh_isblockclear(ubh,begin,block)
(!_ubh_isblockset_(uspi,ubh,begin,block))
@@ -483,7 +483,7 @@ static inline int _ubh_isblockset_(struct
ufs_sb_private_info * uspi,
mask = 0x01 << (block & 0x07);
return (*ubh_get_addr (ubh, begin + (block >> 3)) &
mask) == mask;
}
- return 0;
+ return 0;
}
#define ubh_clrblock(ubh,begin,block) _ubh_clrblock_(uspi,ubh,begin,block)
@@ -492,8 +492,8 @@ static inline void _ubh_clrblock_(struct
ufs_sb_private_info * uspi,
{
switch (uspi->s_fpb) {
case 8:
- *ubh_get_addr (ubh, begin + block) = 0x00;
- return;
+ *ubh_get_addr (ubh, begin + block) = 0x00;
+ return;
case 4:
*ubh_get_addr (ubh, begin + (block >> 1)) &= ~(0x0f <<
((block & 0x01) << 2));
return;
@@ -531,9 +531,9 @@ static inline void ufs_fragacct (struct
super_block * sb, unsigned blockmap,
{
struct ufs_sb_private_info * uspi;
unsigned fragsize, pos;
-
+
uspi = UFS_SB(sb)->s_uspi;
-
+
fragsize = 0;
for (pos = 0; pos < uspi->s_fpb; pos++) {
if (blockmap & (1 << pos)) {
diff --git a/include/asm-generic/bitops/find.h
b/include/asm-generic/bitops/find.h
index 9fdf21302fdf..ca18b2ec954c 100644
--- a/include/asm-generic/bitops/find.h
+++ b/include/asm-generic/bitops/find.h
@@ -16,6 +16,20 @@ extern unsigned long find_next_bit(const unsigned
long *addr, unsigned long
size, unsigned long offset);
#endif
+#ifndef find_prev_bit
+/**
+ * find_prev_bit - find the prev set bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number for the prev set bit
+ * If no bits are set, returns @size.
+ */
+extern unsigned long find_prev_bit(const unsigned long *addr, unsigned long
+ size, unsigned long offset);
+#endif
+
#ifndef find_next_and_bit
/**
* find_next_and_bit - find the next set bit in both memory regions
@@ -32,6 +46,22 @@ extern unsigned long find_next_and_bit(const
unsigned long *addr1,
unsigned long offset);
#endif
+#ifndef find_prev_and_bit
+/**
+ * find_prev_and_bit - find the prev set bit in both memory regions
+ * @addr1: The first address to base the search on
+ * @addr2: The second address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number for the prev set bit
+ * If no bits are set, returns @size.
+ */
+extern unsigned long find_prev_and_bit(const unsigned long *addr1,
+ const unsigned long *addr2, unsigned long size,
+ unsigned long offset);
+#endif
+
#ifndef find_next_zero_bit
/**
* find_next_zero_bit - find the next cleared bit in a memory region
@@ -46,6 +76,20 @@ extern unsigned long find_next_zero_bit(const
unsigned long *addr, unsigned
long size, unsigned long offset);
#endif
+#ifndef find_prev_zero_bit
+/**
+ * find_prev_zero_bit - find the prev cleared bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number of the prev zero bit
+ * If no bits are zero, returns @size.
+ */
+extern unsigned long find_prev_zero_bit(const unsigned long *addr, unsigned
+ long size, unsigned long offset);
+#endif
+
#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
/**
@@ -80,6 +124,31 @@ extern unsigned long find_first_zero_bit(const
unsigned long *addr,
#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
+#ifndef find_last_bit
+/**
+ * find_last_bit - find the last set bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The number of bits to search
+ *
+ * Returns the bit number of the last set bit, or size.
+ */
+extern unsigned long find_last_bit(const unsigned long *addr,
+ unsigned long size);
+#endif
+
+#ifndef find_last_zero_bit
+/**
+ * find_last_zero_bit - find the last cleared bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum number of bits to search
+ *
+ * Returns the bit number of the first cleared bit.
+ * If no bits are zero, returns @size.
+ */
+extern unsigned long find_last_zero_bit(const unsigned long *addr,
+ unsigned long size);
+#endif
+
/**
* find_next_clump8 - find next 8-bit clump with set bits in a memory region
* @clump: location to store copy of found clump
diff --git a/include/asm-generic/bitops/le.h b/include/asm-generic/bitops/le.h
index 188d3eba3ace..d0bd15bc34d9 100644
--- a/include/asm-generic/bitops/le.h
+++ b/include/asm-generic/bitops/le.h
@@ -27,6 +27,24 @@ static inline unsigned long
find_first_zero_bit_le(const void *addr,
return find_first_zero_bit(addr, size);
}
+static inline unsigned long find_prev_zero_bit_le(const void *addr,
+ unsigned long size, unsigned long offset)
+{
+ return find_prev_zero_bit(addr, size, offset);
+}
+
+static inline unsigned long find_prev_bit_le(const void *addr,
+ unsigned long size, unsigned long offset)
+{
+ return find_prev_bit(addr, size, offset);
+}
+
+static inline unsigned long find_last_zero_bit_le(const void *addr,
+ unsigned long size)
+{
+ return find_last_zero_bit(addr, size);
+}
+
#elif defined(__BIG_ENDIAN)
#define BITOP_LE_SWIZZLE ((BITS_PER_LONG-1) & ~0x7)
@@ -41,11 +59,26 @@ extern unsigned long find_next_bit_le(const void *addr,
unsigned long size, unsigned long offset);
#endif
+#ifndef find_prev_zero_bit_le
+extern unsigned long find_prev_zero_bit_le(const void *addr,
+ unsigned long size, unsigned long offset);
+#endif
+
+#ifndef find_prev_bit_le
+extern unsigned long find_prev_bit_le(const void *addr,
+ unsigned long size, unsigned long offset);
+#endif
+
#ifndef find_first_zero_bit_le
#define find_first_zero_bit_le(addr, size) \
find_next_zero_bit_le((addr), (size), 0)
#endif
+#ifndef find_last_zero_bit_le
+#define find_last_zero_bit_le(addr, size) \
+ find_prev_zero_bit_le((addr), (size), (size - 1))
+#endif
+
#else
#error "Please fix <asm/byteorder.h>"
#endif
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 5b74bdf159d6..124c68929861 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -50,6 +50,28 @@ extern unsigned long __sw_hweight64(__u64 w);
(bit) < (size); \
(bit) = find_next_zero_bit((addr), (size), (bit) + 1))
+#define for_each_set_bit_reverse(bit, addr, size) \
+ for ((bit) = find_last_bit((addr), (size)); \
+ (bit) < (size); \
+ (bit) = find_prev_bit((addr), (size), (bit)))
+
+/* same as for_each_set_bit_reverse() but use bit as value to start with */
+#define for_each_set_bit_from_reverse(bit, addr, size) \
+ for ((bit) = find_prev_bit((addr), (size), (bit)); \
+ (bit) < (size); \
+ (bit) = find_prev_bit((addr), (size), (bit - 1)))
+
+#define for_each_clear_bit_reverse(bit, addr, size) \
+ for ((bit) = find_last_zero_bit((addr), (size)); \
+ (bit) < (size); \
+ (bit) = find_prev_zero_bit((addr), (size), (bit)))
+
+/* same as for_each_clear_bit_reverse() but use bit as value to start with */
+#define for_each_clear_bit_from_reverse(bit, addr, size) \
+ for ((bit) = find_prev_zero_bit((addr), (size), (bit)); \
+ (bit) < (size); \
+ (bit) = find_next_zero_bit((addr), (size), (bit - 1)))
+
/**
* for_each_set_clump8 - iterate over bitmap for each 8-bit clump with set bits
* @start: bit offset to start search and to store the current iteration offset
@@ -283,17 +305,5 @@ static __always_inline void __assign_bit(long nr,
volatile unsigned long *addr,
})
#endif
-#ifndef find_last_bit
-/**
- * find_last_bit - find the last set bit in a memory region
- * @addr: The address to start the search at
- * @size: The number of bits to search
- *
- * Returns the bit number of the last set bit, or size.
- */
-extern unsigned long find_last_bit(const unsigned long *addr,
- unsigned long size);
-#endif
-
#endif /* __KERNEL__ */
#endif
diff --git a/lib/find_bit.c b/lib/find_bit.c
index 4a8751010d59..cbe06abd3d21 100644
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -69,6 +69,58 @@ static unsigned long _find_next_bit(const unsigned
long *addr1,
}
#endif
+#if !defined(find_prev_bit) || !defined(find_prev_zero_bit) ||
\
+ !defined(find_prev_bit_le) || !defined(find_prev_zero_bit_le)
|| \
+ !defined(find_prev_and_bit)
+/*
+ * This is a common helper function for find_prev_bit, find_prev_zero_bit, and
+ * find_prev_and_bit. The differences are:
+ * - The "invert" argument, which is XORed with each fetched word before
+ * searching it for one bits.
+ * - The optional "addr2", which is anded with "addr1" if present.
+ */
+static unsigned long _find_prev_bit(const unsigned long *addr1,
+ const unsigned long *addr2, unsigned long nbits,
+ unsigned long start, unsigned long invert, unsigned long le)
+{
+ unsigned long tmp, mask;
+
+ if (unlikely(start >= nbits))
+ return nbits;
+
+ tmp = addr1[start / BITS_PER_LONG];
+ if (addr2)
+ tmp &= addr2[start / BITS_PER_LONG];
+ tmp ^= invert;
+
+ /* Handle 1st word. */
+ mask = BITMAP_LAST_WORD_MASK(start + 1);
+ if (le)
+ mask = swab(mask);
+
+ tmp &= mask;
+
+ start = round_down(start, BITS_PER_LONG);
+
+ while (!tmp) {
+ start -= BITS_PER_LONG;
+ if (start >= nbits)
+ return nbits;
+
+ tmp = addr1[start / BITS_PER_LONG];
+ if (addr2)
+ tmp &= addr2[start / BITS_PER_LONG];
+ tmp ^= invert;
+ }
+
+ if (le)
+ tmp = swab(tmp);
+
+ return start + __fls(tmp);
+}
+#endif
+
+
#ifndef find_next_bit
/*
* Find the next set bit in a memory region.
@@ -81,6 +133,18 @@ unsigned long find_next_bit(const unsigned long
*addr, unsigned long size,
EXPORT_SYMBOL(find_next_bit);
#endif
+#ifndef find_prev_bit
+/*
+ * Find the prev set bit in a memory region.
+ */
+unsigned long find_prev_bit(const unsigned long *addr, unsigned long size,
+ unsigned long offset)
+{
+ return _find_prev_bit(addr, NULL, size, offset, 0UL, 0);
+}
+EXPORT_SYMBOL(find_prev_bit);
+#endif
+
#ifndef find_next_zero_bit
unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
@@ -90,7 +154,16 @@ unsigned long find_next_zero_bit(const unsigned
long *addr, unsigned long size,
EXPORT_SYMBOL(find_next_zero_bit);
#endif
-#if !defined(find_next_and_bit)
+#ifndef find_prev_zero_bit
+unsigned long find_prev_zero_bit(const unsigned long *addr, unsigned long size,
+ unsigned long offset)
+{
+ return _find_prev_bit(addr, NULL, size, offset, ~0UL, 0);
+}
+EXPORT_SYMBOL(find_prev_zero_bit);
+#endif
+
+#ifndef find_next_and_bit
unsigned long find_next_and_bit(const unsigned long *addr1,
const unsigned long *addr2, unsigned long size,
unsigned long offset)
@@ -100,6 +173,16 @@ unsigned long find_next_and_bit(const unsigned long *addr1,
EXPORT_SYMBOL(find_next_and_bit);
#endif
+#ifndef find_prev_and_bit
+unsigned long find_prev_and_bit(const unsigned long *addr1,
+ const unsigned long *addr2, unsigned long size,
+ unsigned long offset)
+{
+ return _find_prev_bit(addr1, addr2, size, offset, 0UL, 0);
+}
+EXPORT_SYMBOL(find_prev_and_bit);
+#endif
+
#ifndef find_first_bit
/*
* Find the first set bit in a memory region.
@@ -141,7 +224,7 @@ unsigned long find_last_bit(const unsigned long
*addr, unsigned long size)
{
if (size) {
unsigned long val = BITMAP_LAST_WORD_MASK(size);
- unsigned long idx = (size-1) / BITS_PER_LONG;
+ unsigned long idx = (size - 1) / BITS_PER_LONG;
do {
val &= addr[idx];
@@ -156,6 +239,27 @@ unsigned long find_last_bit(const unsigned long
*addr, unsigned long size)
EXPORT_SYMBOL(find_last_bit);
#endif
+#ifndef find_last_zero_bit
+unsigned long find_last_zero_bit(const unsigned long *addr, unsigned long size)
+{
+ if (size) {
+ unsigned long val = BITMAP_LAST_WORD_MASK(size);
+ unsigned long idx = (size - 1) / BITS_PER_LONG;
+
+ do {
+ val &= ~addr[idx];
+ if (val)
+ return idx * BITS_PER_LONG + __fls(val);
+
+ val = ~0ul;
+ } while (idx--);
+ }
+
+ return size;
+}
+EXPORT_SYMBOL(find_last_zero_bit);
+#endif
+
#ifdef __BIG_ENDIAN
#ifndef find_next_zero_bit_le
@@ -167,6 +271,15 @@ unsigned long find_next_zero_bit_le(const void
*addr, unsigned
EXPORT_SYMBOL(find_next_zero_bit_le);
#endif
+#ifndef find_prev_zero_bit_le
+unsigned long find_prev_zero_bit_le(const void *addr, unsigned
+ long size, unsigned long offset)
+{
+ return _find_prev_bit(addr, NULL, size, offset, ~0UL, 1);
+}
+EXPORT_SYMBOL(find_prev_zero_bit_le);
+#endif
+
#ifndef find_next_bit_le
unsigned long find_next_bit_le(const void *addr, unsigned
long size, unsigned long offset)
@@ -176,6 +289,15 @@ unsigned long find_next_bit_le(const void *addr, unsigned
EXPORT_SYMBOL(find_next_bit_le);
#endif
+#ifdef find_prev_bit_le
+unsigned long find_prev_bit_le(const void *addr, unsigned
+ long size, unsigned long offset)
+{
+ return _find_prev_bit(addr, NULL, size, offset, 0UL, 1);
+}
+EXPORT_SYMBOL(find_prev_bit_le);
+#endif
+
#endif /* __BIG_ENDIAN */
unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
--
2.29.2
On Wed, Dec 02, 2020 at 10:10:09AM +0900, Yun Levi wrote:
> Inspired find_next_*bit function series, add find_prev_*_bit series.
> I'm not sure whether it'll be used right now But, I add these functions
> for future usage.
This patch has few issues:
- it has more things than described (should be several patches instead)
- new functionality can be split logically to couple or more pieces as well
- it proposes functionality w/o user (dead code)
--
With Best Regards,
Andy Shevchenko
On 02/12/2020 10.47, Andy Shevchenko wrote:
> On Wed, Dec 02, 2020 at 10:10:09AM +0900, Yun Levi wrote:
>> Inspired find_next_*bit function series, add find_prev_*_bit series.
>> I'm not sure whether it'll be used right now But, I add these functions
>> for future usage.
>
> This patch has few issues:
> - it has more things than described (should be several patches instead)
> - new functionality can be split logically to couple or more pieces as well
> - it proposes functionality w/o user (dead code)
Yeah, the last point means it can't be applied - please submit it again
if and when you have an actual use case. And I'll add
- it lacks extension of the bitmap test module to cover the new
functions (that also wants to be a separate patch).
Rasmus
Thanks for kind advice. But I'm so afraid to have questions below:
> - it proposes functionality w/o user (dead code)
Actually, I add these series functions to rewrite some of the
resource clean-up routine.
A typical case is ethtool_set_per_queue_coalesce 's rollback label.
Could this usage be an actual use case?
>- it lacks extension of the bitmap test module to cover the new
> functions (that also wants to be a separate patch).
I see, then Could I add some of testcase on lib/test_bitops.c for testing?
On Wed, Dec 2, 2020 at 7:04 PM Rasmus Villemoes
<[email protected]> wrote:
>
> On 02/12/2020 10.47, Andy Shevchenko wrote:
> > On Wed, Dec 02, 2020 at 10:10:09AM +0900, Yun Levi wrote:
> >> Inspired find_next_*bit function series, add find_prev_*_bit series.
> >> I'm not sure whether it'll be used right now But, I add these functions
> >> for future usage.
> >
> > This patch has few issues:
> > - it has more things than described (should be several patches instead)
> > - new functionality can be split logically to couple or more pieces as well
> > - it proposes functionality w/o user (dead code)
>
> Yeah, the last point means it can't be applied - please submit it again
> if and when you have an actual use case. And I'll add
>
> - it lacks extension of the bitmap test module to cover the new
> functions (that also wants to be a separate patch).
>
> Rasmus
On Wed, Dec 02, 2020 at 08:50:24PM +0900, Yun Levi wrote:
> Thanks for kind advice. But I'm so afraid to have questions below:
>
> > - it proposes functionality w/o user (dead code)
> Actually, I add these series functions to rewrite some of the
> resource clean-up routine.
> A typical case is ethtool_set_per_queue_coalesce 's rollback label.
> Could this usage be an actual use case?
Then create it as a patch in the series and in cover letter (0 message when you
supply --cover-letter to your `git format-patch ...` command line) mention
this.
> >- it lacks extension of the bitmap test module to cover the new
> > functions (that also wants to be a separate patch).
> I see, then Could I add some of testcase on lib/test_bitops.c for testing?
Sounds good to me. Most important is to have test cases, then we will see which
test suite is the best fit, but as I said sounds like a good shot.
And please do not top post in replies!
> On Wed, Dec 2, 2020 at 7:04 PM Rasmus Villemoes
> <[email protected]> wrote:
> >
> > On 02/12/2020 10.47, Andy Shevchenko wrote:
> > > On Wed, Dec 02, 2020 at 10:10:09AM +0900, Yun Levi wrote:
> > >> Inspired find_next_*bit function series, add find_prev_*_bit series.
> > >> I'm not sure whether it'll be used right now But, I add these functions
> > >> for future usage.
> > >
> > > This patch has few issues:
> > > - it has more things than described (should be several patches instead)
> > > - new functionality can be split logically to couple or more pieces as well
> > > - it proposes functionality w/o user (dead code)
> >
> > Yeah, the last point means it can't be applied - please submit it again
> > if and when you have an actual use case. And I'll add
> >
> > - it lacks extension of the bitmap test module to cover the new
> > functions (that also wants to be a separate patch).
--
With Best Regards,
Andy Shevchenko
On Wed, Dec 02, 2020 at 09:26:05AM -0800, Yury Norov wrote:
> On Wed, Dec 2, 2020 at 3:50 AM Yun Levi <[email protected]> wrote:
...
> I think this patch has some good catches. We definitely need to implement
> find_last_zero_bit(), as it is used by fs/ufs, and their local
> implementation is not optimal.
Side note: speaking of performance, any plans to fix for_each_*_bit*() for
cases when the nbits is known to be <= BITS_PER_LONG?
Now it makes an awful code generation (something like few hundred bytes of
code).
--
With Best Regards,
Andy Shevchenko
On Thu, Dec 3, 2020 at 2:36 AM Andy Shevchenko
<[email protected]> wrote:
>
> On Wed, Dec 02, 2020 at 09:26:05AM -0800, Yury Norov wrote:
> > On Wed, Dec 2, 2020 at 3:50 AM Yun Levi <[email protected]> wrote:
>
> ...
>
> > I think this patch has some good catches. We definitely need to implement
> > find_last_zero_bit(), as it is used by fs/ufs, and their local
> > implementation is not optimal.
>
> Side note: speaking of performance, any plans to fix for_each_*_bit*() for
> cases when the nbits is known to be <= BITS_PER_LONG?
>
> Now it makes an awful code generation (something like few hundred bytes of
> code).
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
> Side note: speaking of performance, any plans to fix for_each_*_bit*() for
> cases when the nbits is known to be <= BITS_PER_LONG?
Frankly Speaking, I don't have an idea in now.....
Could you share your idea or wisdom?
Thanks.
Levi.
On Thu, Dec 03, 2020 at 03:27:33AM +0900, Yun Levi wrote:
> On Thu, Dec 3, 2020 at 2:36 AM Andy Shevchenko
> <[email protected]> wrote:
> > On Wed, Dec 02, 2020 at 09:26:05AM -0800, Yury Norov wrote:
...
> > Side note: speaking of performance, any plans to fix for_each_*_bit*() for
> > cases when the nbits is known to be <= BITS_PER_LONG?
> >
> > Now it makes an awful code generation (something like few hundred bytes of
> > code).
> Frankly Speaking, I don't have an idea in now.....
> Could you share your idea or wisdom?
Something like (I may be mistaken by names, etc, I'm not a compiler expert,
and this is in pseudo language, I don't remember all API names by hart,
just to express the idea) as a rough first step
__builtin_constant(nbits, find_next_set_bit_long, find_next_set_bit)
find_next_set_bit_long()
{
unsigned long v = BIT_LAST_WORD(i);
return ffs_long(v);
}
Same for find_first_set_bit() -> map it to ffs_long().
And I believe it can be optimized more.
--
With Best Regards,
Andy Shevchenko
On Wed, Dec 02, 2020 at 08:51:27PM +0200, Andy Shevchenko wrote:
> On Thu, Dec 03, 2020 at 03:27:33AM +0900, Yun Levi wrote:
> > On Thu, Dec 3, 2020 at 2:36 AM Andy Shevchenko
> > <[email protected]> wrote:
> > > On Wed, Dec 02, 2020 at 09:26:05AM -0800, Yury Norov wrote:
...
> > > Side note: speaking of performance, any plans to fix for_each_*_bit*() for
> > > cases when the nbits is known to be <= BITS_PER_LONG?
> > >
> > > Now it makes an awful code generation (something like few hundred bytes of
> > > code).
>
> > Frankly Speaking, I don't have an idea in now.....
> > Could you share your idea or wisdom?
>
> Something like (I may be mistaken by names, etc, I'm not a compiler expert,
> and this is in pseudo language, I don't remember all API names by hart,
> just to express the idea) as a rough first step
>
> __builtin_constant(nbits, find_next_set_bit_long, find_next_set_bit)
>
> find_next_set_bit_long()
> {
> unsigned long v = BIT_LAST_WORD(i);
> return ffs_long(v);
> }
>
> Same for find_first_set_bit() -> map it to ffs_long().
>
> And I believe it can be optimized more.
Btw it will also require to reconsider test cases where such constant small
nbits values are passed (forcing compiler to avoid optimization somehow, one
way is to try random nbits for some test cases).
--
With Best Regards,
Andy Shevchenko
On Thu, Dec 3, 2020 at 3:55 AM Andy Shevchenko
<[email protected]> wrote:
>
> On Wed, Dec 02, 2020 at 08:51:27PM +0200, Andy Shevchenko wrote:
> > On Thu, Dec 03, 2020 at 03:27:33AM +0900, Yun Levi wrote:
> > > On Thu, Dec 3, 2020 at 2:36 AM Andy Shevchenko
> > > <[email protected]> wrote:
> > > > On Wed, Dec 02, 2020 at 09:26:05AM -0800, Yury Norov wrote:
>
> ...
>
> > > > Side note: speaking of performance, any plans to fix for_each_*_bit*() for
> > > > cases when the nbits is known to be <= BITS_PER_LONG?
> > > >
> > > > Now it makes an awful code generation (something like few hundred bytes of
> > > > code).
> >
> > > Frankly Speaking, I don't have an idea in now.....
> > > Could you share your idea or wisdom?
> >
> > Something like (I may be mistaken by names, etc, I'm not a compiler expert,
> > and this is in pseudo language, I don't remember all API names by hart,
> > just to express the idea) as a rough first step
> >
> > __builtin_constant(nbits, find_next_set_bit_long, find_next_set_bit)
> >
> > find_next_set_bit_long()
> > {
> > unsigned long v = BIT_LAST_WORD(i);
> > return ffs_long(v);
> > }
> >
I think this idea is hard to apply to find_next_set_bit.
because __builtin_constant should be not only to size but also to offset.
though we find size && offset is const under BITS_PER_LONG,
I'm not sure it could be implemented as const expression..
> > Same for find_first_set_bit() -> map it to ffs_long().
> >
> > And I believe it can be optimized more.
In case of the find_first_set_bit, I think it would be possible,
But I think it much better to separate as another patch set.
So I want to focus on adding find_prev_*_bit, find_last_zero_bit to
this patchset and mail-thread. Frankly speaking I need time to see
that suggestion and think so, in next patch v2,
it wouldn't be included.
>
> Btw it will also require to reconsider test cases where such constant small
> nbits values are passed (forcing compiler to avoid optimization somehow, one
> way is to try random nbits for some test cases).
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
if my understanding and attitude are wrong, I really apologize for my
rudeness and stubbornness but please let me know what thing is wrong.
Sincerely
Levi.