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Remove fls(), use pg_leftmost_one_pos32() instead.

Browse Source 
Commit 4f658dc8 provided the traditional BSD fls() function in
src/port/fls.c so it could be used in several places.  Later we added a
bunch of similar facilities in pg_bitutils.h, based on compiler
builtins that map to hardware instructions.  It's a bit confusing to
have both 1-based and 0-based variants of this operation in use in
different parts of the tree, and neither is blessed by a standard.
Let's drop fls.c and the configure probe, and reuse the newer code.

Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CA%2BhUKG%2B7dSX1XF8yFGmYk-%3D48dbjH2kmzZj16XvhbrWP-9BzRg%40mail.gmail.com
This commit is contained in:
Thomas Munro 2022-07-22 09:41:12 +12:00
parent 3225399021
commit 4f1f5a7f85
11 changed files with 19 additions and 92 deletions
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13
configure vendored
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@ -16771,19 +16771,6 @@ esac
fi
ac_fn_c_check_func "$LINENO" "fls" "ac_cv_func_fls"
if test "x$ac_cv_func_fls" = xyes; then :
$as_echo "#define HAVE_FLS 1" >>confdefs.h
else
case " $LIBOBJS " in
*" fls.$ac_objext "* ) ;;
*) LIBOBJS="$LIBOBJS fls.$ac_objext"
;;
esac
fi
ac_fn_c_check_func "$LINENO" "getopt" "ac_cv_func_getopt"
if test "x$ac_cv_func_getopt" = xyes; then :
$as_echo "#define HAVE_GETOPT 1" >>confdefs.h

1
configure.ac
View File

@ -1911,7 +1911,6 @@ fi
AC_REPLACE_FUNCS(m4_normalize([
dlopen
explicit_bzero
fls
getopt
getpeereid
getrusage

2
src/backend/access/hash/hashutil.c
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@ -436,7 +436,7 @@ _hash_get_oldblock_from_newbucket(Relation rel, Bucket new_bucket)
* started. Masking the most significant bit of new bucket would give us
* old bucket.
*/
mask = (((uint32) 1) << (fls(new_bucket) - 1)) - 1;
mask = (((uint32) 1) << pg_leftmost_one_pos32(new_bucket)) - 1;
old_bucket = new_bucket & mask;
metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ, LH_META_PAGE);

5
src/backend/optimizer/path/allpaths.c
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@ -47,6 +47,7 @@
#include "parser/parsetree.h"
#include "partitioning/partbounds.h"
#include "partitioning/partprune.h"
#include "port/pg_bitutils.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"
@ -1491,7 +1492,7 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
if (enable_parallel_append)
{
parallel_workers = Max(parallel_workers,
fls(list_length(live_childrels)));
pg_leftmost_one_pos32(list_length(live_childrels)) + 1);
parallel_workers = Min(parallel_workers,
max_parallel_workers_per_gather);
}
@ -1542,7 +1543,7 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
* the planned number of parallel workers.
*/
parallel_workers = Max(parallel_workers,
fls(list_length(live_childrels)));
pg_leftmost_one_pos32(list_length(live_childrels)) + 1);
parallel_workers = Min(parallel_workers,
max_parallel_workers_per_gather);
Assert(parallel_workers > 0);

2
src/backend/optimizer/prep/prepunion.c
View File

@ -675,7 +675,7 @@ generate_union_paths(SetOperationStmt *op, PlannerInfo *root,
if (enable_parallel_append)
{
parallel_workers = Max(parallel_workers,
fls(list_length(partial_pathlist)));
pg_leftmost_one_pos32(list_length(partial_pathlist)) + 1);
parallel_workers = Min(parallel_workers,
max_parallel_workers_per_gather);
}

14
src/backend/utils/mmgr/dsa.c
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@ -51,6 +51,7 @@
#include "postgres.h"
#include "port/atomics.h"
#include "port/pg_bitutils.h"
#include "storage/dsm.h"
#include "storage/ipc.h"
#include "storage/lwlock.h"
@ -137,7 +138,18 @@ typedef size_t dsa_segment_index;
* free pages? There is no point in looking in segments in lower bins; they
* definitely can't service a request for n free pages.
*/
#define contiguous_pages_to_segment_bin(n) Min(fls(n), DSA_NUM_SEGMENT_BINS - 1)
static inline size_t
contiguous_pages_to_segment_bin(size_t n)
{
size_t bin;
if (n == 0)
bin = 0;
else
bin = pg_leftmost_one_pos_size_t(n) + 1;
return Min(bin, DSA_NUM_SEGMENT_BINS - 1);
}
/* Macros for access to locks. */
#define DSA_AREA_LOCK(area) (&area->control->lock)

3
src/include/pg_config.h.in
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@ -191,9 +191,6 @@
/* Define to 1 if you have the `fdatasync' function. */
#undef HAVE_FDATASYNC
/* Define to 1 if you have the `fls' function. */
#undef HAVE_FLS
/* Define to 1 if fseeko (and presumably ftello) exists and is declared. */
#undef HAVE_FSEEKO

4
src/include/port.h
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@ -366,10 +366,6 @@ extern int gettimeofday(struct timeval *tp, struct timezone *tzp);
#define pgoff_t off_t
#endif
#ifndef HAVE_FLS
extern int fls(int mask);
#endif
#ifndef HAVE_GETPEEREID
/* On Windows, Perl might have incompatible definitions of uid_t and gid_t. */
#ifndef PLPERL_HAVE_UID_GID

64
src/port/fls.c
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@ -1,64 +0,0 @@
/*-------------------------------------------------------------------------
*
* fls.c
* finds the last (most significant) bit that is set
*
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
*
*
* IDENTIFICATION
* src/port/fls.c
*
* This file was taken from FreeBSD to provide an implementation of fls()
* for platforms that lack it. Note that the operating system's version may
* be substantially more efficient than ours, since some platforms have an
* assembly instruction that does exactly this.
*
* The FreeBSD copyright terms follow.
*/
/*-
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "c.h"
/*
* Find Last Set bit
*/
int
fls(int mask)
{
int bit;
if (mask == 0)
return (0);
for (bit = 1; mask != 1; bit++)
mask = (unsigned int) mask >> 1;
return (bit);
}

2
src/tools/msvc/Mkvcbuild.pm
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@ -99,7 +99,7 @@ sub mkvcbuild
$solution = CreateSolution($vsVersion, $config);
our @pgportfiles = qw(
chklocale.c explicit_bzero.c fls.c fdatasync.c
chklocale.c explicit_bzero.c fdatasync.c
getpeereid.c getrusage.c inet_aton.c
getaddrinfo.c gettimeofday.c inet_net_ntop.c kill.c open.c
snprintf.c strlcat.c strlcpy.c dirmod.c noblock.c path.c

1
src/tools/msvc/Solution.pm
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@ -258,7 +258,6 @@ sub GenerateFiles
HAVE_EXECINFO_H => undef,
HAVE_EXPLICIT_BZERO => undef,
HAVE_FDATASYNC => 1,
HAVE_FLS => undef,
HAVE_FSEEKO => 1,
HAVE_FUNCNAME__FUNC => undef,
HAVE_FUNCNAME__FUNCTION => 1,