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Remove fls(), use pg_leftmost_one_pos32() instead. 

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
configure vendored
View File

@ -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
View File

@ -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
View File

@ -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
View File

@ -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
View File

@ -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
View File

@ -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
View File

@ -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
View File

@ -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
View File

@ -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,