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Commit4f658dc

Browse files
committed
Support fls().
The immediate impetus for this is that Noah Misch's patch to elideunnecessary table and index rebuilds when changing typmod for temporaltypes uses it; and this is extracted from that patch, with somefurther commentary by me. But it seems logically separate from theremainder of the patch, so I'm committing it separately; this is notthe first time someone has wanted fls() in the backend and probablywon't be the last.If we end up using this in more performance-critical spots it may beworthwhile to add some architecture-specific optimizations to oursrc/port version of fls() - e.g. any x86 platform can implement thisusing the assembly instruction BSRL. But performance won't mattera bit for assessing typmod changes, so I'm not worried about thatright now.
1 parentf7d7dad commit4f658dc

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5 files changed

+74
-2
lines changed

5 files changed

+74
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‎configure

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -20833,7 +20833,8 @@ LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
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20836-
for ac_func in crypt getopt getrusage inet_aton random rint srandom strdup strerror strlcat strlcpy strtol strtoul
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for ac_func in crypt fls getopt getrusage inet_aton random rint srandom strdup strerror strlcat strlcpy strtol strtoul
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do
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as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
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{ $as_echo "$as_me:$LINENO: checking for $ac_func" >&5

‎configure.in

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Original file line numberDiff line numberDiff line change
@@ -1335,7 +1335,7 @@ fi
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pgac_save_LIBS="$LIBS"
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LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
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AC_REPLACE_FUNCS([crypt getopt getrusage inet_aton random rint srandom strdup strerror strlcat strlcpy strtol strtoul])
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AC_REPLACE_FUNCS([cryptflsgetopt getrusage inet_aton random rint srandom strdup strerror strlcat strlcpy strtol strtoul])
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case $host_os in
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‎src/include/pg_config.h.in

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Original file line numberDiff line numberDiff line change
@@ -158,6 +158,9 @@
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/* Define to 1 if you have the `fdatasync' function. */
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#undef HAVE_FDATASYNC
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/* Define to 1 if you have the `fls' function. */
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#undef HAVE_FLS
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/* Define to 1 if you have the `fpclass' function. */
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#undef HAVE_FPCLASS
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‎src/include/port.h

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Original file line numberDiff line numberDiff line change
@@ -396,6 +396,10 @@ extern double pg_erand48(unsigned short xseed[3]);
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externlongpg_lrand48(void);
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externvoidpg_srand48(longseed);
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#ifndefHAVE_FLS
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externintfls(intmask);
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#endif
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#ifndefHAVE_FSEEKO
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#definefseeko(a,b,c) fseek(a, b, c)
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#defineftello(a)ftell(a)

‎src/port/fls.c

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,64 @@
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/*-------------------------------------------------------------------------
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*
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* fls.c
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* finds the last (most significant) bit that is set
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*
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* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
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*
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*
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* IDENTIFICATION
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* src/port/fls.c
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*
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* This file was taken from FreeBSD to provide an implementation of fls()
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* for platforms that lack it. Note that the operating system's version may
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* be substantially more efficient thatn ours, since some platforms have an
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* assembly instruction that does exactly this.
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*
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* The FreeBSD copyright terms follow.
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*/
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/*-
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* Copyright (c) 1990, 1993
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*The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include"c.h"
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/*
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* Find Last Set bit
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*/
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int
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fls(intmask)
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{
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intbit;
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if (mask==0)
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return (0);
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for (bit=1;mask!=1;bit++)
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mask= (unsignedint)mask >>1;
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return (bit);
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}

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