Test for the compiler builtins __builtin_clz, __builtin_ctz, and
__builtin_popcount, and make use of these in preference to
handwritten C code if they're available. Create src/port
infrastructure for "leftmost one", "rightmost one", and "popcount"
so as to centralize these decisions.
On x86_64, __builtin_popcount generally won't make use of the POPCNT
opcode because that's not universally supported yet. Provide code
that checks CPUID and then calls POPCNT via asm() if available.
This requires indirecting through a function pointer, which is
an annoying amount of overhead for a one-instruction operation,
but it's probably not worth working harder than this for our
current use-cases.
I'm not sure we've found all the existing places that could profit
from this new infrastructure; but we at least touched all the
ones that used copied-and-pasted versions of the bitmapset.c code,
and got rid of multiple copies of the associated constant arrays.
While at it, replace c-compiler.m4's one-per-builtin-function
macros with a single one that can handle all the cases we need
to worry about so far. Also, because I'm paranoid, make those
checks into AC_LINK checks rather than just AC_COMPILE; the
former coding failed to verify that libgcc has support for the
builtin, in cases where it's not inline code.
David Rowley, Thomas Munro, Alvaro Herrera, Tom Lane
Discussion: https://postgr.es/m/CAKJS1f9WTAGG1tPeJnD18hiQW5gAk59fQ6WK-vfdAKEHyRg2RA@mail.gmail.com
Deal with silent-underflow errors in float4 for cygwin and mingw by
using our strtof() wrapper; deal with misrounding errors by adding
them to the resultmap. Some slight reorganization of declarations was
done to avoid duplicating material between cygwin.h and win32_port.h.
While here, remove from the resultmap all references to
float8-small-is-zero; inspection of cygwin output suggests it's no
longer required there, and the freebsd/netbsd/openbsd entries should
no longer be necessary (these date back to c. 2000). This commit
doesn't remove the file itself nor the documentation references for
it; that will happen in a subsequent commit if all goes well.
This reverts commits fc6c72747a, 109de05cbb, d0b4663c23 and
711bab1e4d.
Somebody will have to try harder before submitting this patch again.
I've spent entirely too much time on it already, and the #ifdef maze yet
to be written in order for it to build at all got on my nerves. The
amount of work needed to get a platform-specific performance improvement
that's barely above the noise level is not worth it.
Split out these new functions in three parts: one in a new file that
uses the compiler builtin and gets compiled with the -mpopcnt compiler
option if it exists; another one that uses the compiler builtin but not
the compiler option; and finally the fallback with open-coded
algorithms.
Split out the configure logic: in the original commit, it was selecting
to use the -mpopcnt compiler switch together with deciding whether to
use the compiler builtin, but those two things are really separate.
Split them out. Also, expose whether the builtin exists to
Makefile.global, so that src/port's Makefile can decide whether to
compile the hw-optimized file.
Remove CPUID test for CTZ/CLZ. Make pg_{right,left}most_ones use either
the compiler intrinsic or open-coded algo; trying to use the
HW-optimized version is a waste of time. Make them static inline
functions.
Discussion: https://postgr.es/m/20190213221719.GA15976@alvherre.pgsql
These opcodes have been around in the AMD world since 2007, and 2008 in
the case of intel. They're supported in GCC and Clang via some __builtin
macros. The opcodes may be unavailable during runtime, in which case we
fall back on a C-based implementation of the code. In order to get the
POPCNT instruction we must pass the -mpopcnt option to the compiler. We
do this only for the pg_bitutils.c file.
David Rowley (with fragments taken from a patch by Thomas Munro)
Discussion: https://postgr.es/m/CAKJS1f9WTAGG1tPeJnD18hiQW5gAk59fQ6WK-vfdAKEHyRg2RA@mail.gmail.com
Using strtod() creates a double-rounding problem; the input decimal
value is first rounded to the nearest double; rounding that to the
nearest float may then give an incorrect result.
An example is that 7.038531e-26 when input via strtod and then rounded
to float4 gives 0xAE43FEp-107 instead of the correct 0xAE43FDp-107.
Values output by earlier PG versions with extra_float_digits=3 should
all be read in with the same values as previously. However, values
supplied by other software using shortest representations could be
mis-read.
On platforms that lack a strtof() entirely, we fall back to the old
incorrect rounding behavior. (As strtof() is required by C99, such
platforms are considered of primarily historical interest.) On VS2013,
some workarounds are used to get correct error handling.
The regression tests now test for the correct input values, so
platforms that lack strtof() will need resultmap entries. An entry for
HP-UX 10 is included (more may be needed).
Reviewed-By: Tom Lane
Discussion: https://postgr.es/m/871s5emitx.fsf@news-spur.riddles.org.uk
Discussion: https://postgr.es/m/87d0owlqpv.fsf@news-spur.riddles.org.uk
Setting them to SIG_IGN seems unlikely to have any beneficial effect
on that platform, and given the signal numbering collision with SIGABRT,
it could easily have bad effects.
Given the lack of field complaints that can be traced to this, I don't
presently feel a need to back-patch.
Discussion: https://postgr.es/m/5627.1542477392@sss.pgh.pa.us
elog.c has long had a private strerror wrapper that handles assorted
possible failures or deficiencies of the platform's strerror. On Windows,
it also knows how to translate Winsock error codes, which the native
strerror does not. Move all this code into src/port/strerror.c and
define strerror() as a macro that invokes it, so that both our frontend
and backend code will have all of this behavior.
I believe this constitutes an actual bug fix on Windows, since AFAICS
our frontend code did not report Winsock error codes properly before this.
However, the main point is to lay the groundwork for implementing %m
in src/port/snprintf.c: the behavior we want %m to have is this one,
not the native strerror's.
Note that this throws away the prior use of src/port/strerror.c,
which was to implement strerror() on platforms lacking it. That's
been dead code for nigh twenty years now, since strerror() was
already required by C89.
We should likewise cause strerror_r to use this behavior, but
I'll tackle that separately.
Patch by me, reviewed by Michael Paquier
Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us
A collection of typos I happened to spot while reading code, as well as
grepping for common mistakes.
Backpatch to all supported versions, as applicable, to avoid conflicts
when backporting other commits in the future.
We include <float.h> in every place that needs isnan(), because MSVC
used to require it. However, since MSVC 2013 that's no longer necessary
(cf. commit cec8394b5c), so we can retire the inclusion to a
version-specific stanza in win32_port.h, where it doesn't need to
pollute random .c files. The header is of course still needed in a few
places for other reasons.
I (Álvaro) removed float.h from a few more files than in Emre's original
patch. This doesn't break the build in my system, but we'll see what
the buildfarm has to say about it all.
Author: Emre Hasegeli
Discussion: https://postgr.es/m/CAE2gYzyc0+5uG+Cd9-BSL7NKC8LSHLNg1Aq2=8ubjnUwut4_iw@mail.gmail.com
The atomics code asserts proper alignment in various places. That's
mainly because the alignment of 64bit integers is not sufficient for
atomic operations on all platforms. Some ABIs only have four byte
alignment, but don't have atomic behavior when crossing page
boundaries.
The flags code isn't affected by that however, as the type alignment
always is sufficient for atomic operations. Nevertheless the code
asserted alignment requirements. Before 8c3debbb it was only broken on
hppa, after it probably affect further platforms.
Thus remove the assertions for pg_atomic_flag operators.
Per buildfarm animal pademelon.
Discussion: https://postgr.es/m/7223.1523124425@sss.pgh.pa.us
Backpatch: 9.5-
The atomics fallback implementation for pg_atomic_flag was broken,
returning the inverted value from pg_atomic_test_set_flag(). This was
unnoticed because a) atomic flags were unused until recently b) the
test code wasn't run when the fallback implementation was in
use (because it didn't allow to test for some edge cases).
Fix the bug, and improve the fallback so it has the same behaviour as
the non-fallback implementation in the problematic edge cases. That
breaks ABI compatibility in the back branches when fallbacks are in
use, but given they were broken until now...
Author: Andres Freund
Reported-by: Daniel Gustafsson
Discussion:
https://postgr.es/m/FB948276-7B32-4B77-83E6-D00167F8EEB4@yesql.sehttps://postgr.es/m/20180406233854.uni2h3mbnveczl32@alap3.anarazel.de
Backpatch: 9.5-, where the atomics abstraction was introduced.
ARMv8 introduced special CPU instructions for calculating CRC-32C. Use
them, when available, for speed.
Like with the similar Intel CRC instructions, several factors affect
whether the instructions can be used. The compiler intrinsics for them must
be supported by the compiler, and the instructions must be supported by the
target architecture. If the compilation target architecture does not
support the instructions, but adding "-march=armv8-a+crc" makes them
available, then we compile the code with a runtime check to determine if
the host we're running on supports them or not.
For the runtime check, use glibc getauxval() function. Unfortunately,
that's not very portable, but I couldn't find any more portable way to do
it. If getauxval() is not available, the CRC instructions will still be
used if the target architecture supports them without any additional
compiler flags, but the runtime check will not be available.
Original patch by Yuqi Gu, heavily modified by me. Reviewed by Andres
Freund, Thomas Munro.
Discussion: https://www.postgresql.org/message-id/HE1PR0801MB1323D171938EABC04FFE7FA9E3110%40HE1PR0801MB1323.eurprd08.prod.outlook.com
Experimentation with modern MinGW (specifically the 5.0.2 version packaged
for Fedora 26) shows that its version of sys/stat.h *does* provide S_IRGRP
and friends, contrary to the expectation of win32_port.h. This results in
an astonishing number of compiler warnings, and perhaps in incorrect code
--- I'm not sure if the nonzero values supplied by MinGW's header actually
do anything. Hence, adjust win32_port.h to only define these macros if
<sys/stat.h> doesn't.
This might be worth back-patching, but given the lack of complaints so
far, I'm not too excited about it.
Commit 0fb54de9a thought that this was only needed in VS2015 and later,
but buildfarm member woodlouse shows that at least VS2013 whines as
well. Let's just define it regardless of MSVC version; it should be
harmless enough in older releases.
Also, in the wake of ed9b3606d, it seems better to put it in win32_port.h
where <winsock2.h> is included.
Since this is only suppressing a pedantic compiler warning, I don't
feel a need for a back-patch.
Discussion: https://postgr.es/m/20124.1510850225@sss.pgh.pa.us
This continues the work of commit 91aec93e6 by getting rid of a lot of
Windows-specific funny business in "section 0". Instead of including
pg_config_os.h in different places depending on platform, let's
standardize on putting it before the system headers, and in consequence
reduce win32.h to just what has to appear before the system headers or
the body of c.h (the latter category seems to include only PGDLLIMPORT
and PGDLLEXPORT). The rest of what was in win32.h is moved to a new
sub-include of port.h, win32_port.h. Some of what was in port.h seems
to better belong there too.
It's possible that I missed some declaration ordering dependency that
needs to be preserved, but hopefully the buildfarm will find that
out in short order.
Unlike the previous commit, no back-patch, since this is just cleanup
not a prerequisite for a bug fix.
Discussion: https://postgr.es/m/29650.1510761080@sss.pgh.pa.us
Upcoming patches are going to address performance issues that involve
slow system provided ntohs/htons etc. To address that expand
pg_bswap.h to provide pg_ntoh{16,32,64}, pg_hton{16,32,64} and
optimize their respective implementations by using compiler intrinsics
for gcc compatible compilers and msvc. Fall back to manual
implementations using shifts etc otherwise.
Additionally remove multiple evaluation hazards from the existing
BSWAP32/64 macros, by replacing them with inline functions when
necessary. In the course of that the naming scheme is changed to
pg_bswap16/32/64.
Author: Andres Freund
Discussion: https://postgr.es/m/20170927172019.gheidqy6xvlxb325@alap3.anarazel.de
In the generic atomic ops that rely on a loop around a CAS primitive,
there's no need to force the initial read of the "old" value to be atomic.
In the typically-rare case that we get a torn value, that simply means
that the first CAS attempt will fail; but it will update "old" to the
atomically-read value, so the next attempt has a chance of succeeding.
It was already being done that way in pg_atomic_exchange_u64_impl(),
but let's duplicate the approach in the rest.
(Given the current coding of the pg_atomic_read functions, this change
is a no-op anyway on popular platforms; it only makes a difference where
pg_atomic_read_u64_impl() is implemented as a CAS.)
In passing, also remove unnecessary take-a-pointer-and-dereference-it
coding in the pg_atomic_read functions. That seems to have been based
on a misunderstanding of what the C standard requires. What actually
matters is that the pointer be declared as pointing to volatile, which
it is.
I don't believe this will change the assembly code at all on x86
platforms (even ignoring the likelihood that these implementations
get overridden by others); but it may help on less-mainstream CPUs.
Discussion: https://postgr.es/m/13707.1504718238@sss.pgh.pa.us
In addition to __sync_fetch_and_add, gcc offers __sync_fetch_and_sub,
__sync_fetch_and_and, and __sync_fetch_and_or, which correspond directly
to primitive atomic ops that we want. Testing shows that in some cases
they generate better code than our generic implementations, so use them.
We've assumed that configure's test for __sync_val_compare_and_swap is
sufficient to allow assuming that __sync_fetch_and_add is available, so
make the same assumption for these functions. Should that prove to be
wrong, we can add more configure tests.
Yura Sokolov, reviewed by Jesper Pedersen and myself
Discussion: https://postgr.es/m/7f65886daca545067f82bf2b463b218d@postgrespro.ru
The pg_atomic_compare_exchange_xxx functions are defined to update
*expected to whatever they read from the target variable. Therefore,
there's no need to do additional explicit reads after we've initialized
the "old" variable. The actual benefit of this is somewhat debatable,
but it seems fairly unlikely to hurt anything, especially since we
will override the generic implementations in most performance-sensitive
cases.
Yura Sokolov, reviewed by Jesper Pedersen and myself
Discussion: https://postgr.es/m/7f65886daca545067f82bf2b463b218d@postgrespro.ru
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4d wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
The new indent version includes numerous fixes thanks to Piotr Stefaniak.
The main changes visible in this commit are:
* Nicer formatting of function-pointer declarations.
* No longer unexpectedly removes spaces in expressions using casts,
sizeof, or offsetof.
* No longer wants to add a space in "struct structname *varname", as
well as some similar cases for const- or volatile-qualified pointers.
* Declarations using PG_USED_FOR_ASSERTS_ONLY are formatted more nicely.
* Fixes bug where comments following declarations were sometimes placed
with no space separating them from the code.
* Fixes some odd decisions for comments following case labels.
* Fixes some cases where comments following code were indented to less
than the expected column 33.
On the less good side, it now tends to put more whitespace around typedef
names that are not listed in typedefs.list. This might encourage us to
put more effort into typedef name collection; it's not really a bug in
indent itself.
There are more changes coming after this round, having to do with comment
indentation and alignment of lines appearing within parentheses. I wanted
to limit the size of the diffs to something that could be reviewed without
one's eyes completely glazing over, so it seemed better to split up the
changes as much as practical.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
This used to mean "Visual C++ except in those parts where Borland C++
was supported where it meant one of those". Now that we don't support
Borland C++ anymore, simplify by using _MSC_VER which is the normal way
to detect Visual C++.
This removes the support for building just libpq using Borland C++ or
Visual C++. This has not worked properly for years, and given the number
of complaints it's clearly not worth the maintenance burden.
Building libpq using the standard MSVC build system is of course still
supported, along with mingw.
When the 64bit atomics simulation is in use, we can't necessarily
guarantee the correct alignment of the atomics due to lack of compiler
support for doing so- that's fine from a safety perspective, because
everything is protected by a lock, but we asserted the alignment in
all cases. Weaken them. Per complaint from Alvaro Herrera.
My #ifdefery for PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY wasn't
sufficient. Fix that. Per complaint from Alexander Korotkov.
When adding atomics back in b64d92f1a, I added 64bit support as
optional; there wasn't yet a direct user in sight. That turned out to
be a bit short-sighted, it'd already have been useful a number of times.
Add a fallback implementation of 64bit atomics, just like the one we
have for 32bit atomics.
Additionally optimize reads/writes to 64bit on a number of platforms
where aligned writes of that size are atomic. This can now be tested
with PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY.
Author: Andres Freund
Reviewed-By: Amit Kapila
Discussion: https://postgr.es/m/20160330230914.GH13305@awork2.anarazel.de
c.h #includes a number of core libc header files, such as <stdio.h>.
There's no point in re-including these after having read postgres.h,
postgres_fe.h, or c.h; so remove code that did so.
While at it, also fix some places that were ignoring our standard pattern
of "include postgres[_fe].h, then system header files, then other Postgres
header files". While there's not any great magic in doing it that way
rather than system headers last, it's silly to have just a few files
deviating from the general pattern. (But I didn't attempt to enforce this
globally, only in files I was touching anyway.)
I'd be the first to say that this is mostly compulsive neatnik-ism,
but over time it might save enough compile cycles to be useful.
We have a portable way of writing uint64 constants, but whoever wrote
this macro didn't know about it.
While at it, fix unsafe under-parenthesization of arguments. That might
be moot, because there are already good reasons not to use the macro on
anything more complicated than a simple variable, but it's still poor
practice.
Per buildfarm warnings.
configure can only probe the existence of gcc intrinsics, not how well
they're implemented, and unfortunately the answer is sometimes "badly".
In particular we've found that multiple compilers fail to implement
char-width __sync_lock_test_and_set() correctly on PPC; and even a correct
implementation would necessarily be pretty inefficient, since that hardware
has only a word-wide primitive to work with.
Given the knowledge we've accumulated in s_lock.h, it appears that it's
best to rely on int-width TAS operations on most non-Intel architectures.
Hence, pick int not char when both are nominally available to us in
generic-gcc.h (note that that code is not used for x86[_64]).
Back-patch to fix regression test failures on FreeBSD/PPC. Ordinarily
back-patching a change like this would be verboten because of ABI breakage.
But since pg_atomic_flag is not yet used in any Postgres data structure,
there's no ABI to break. It seems safer to back-patch to avoid possible
gotchas, if someday we do back-patch something that uses pg_atomic_flag.
Discussion: https://postgr.es/m/25414.1483076673@sss.pgh.pa.us
SCO OpenServer and SCO UnixWare are more or less dead platforms.
We have never had a buildfarm member testing the "sco" port, and
the last "unixware" member was last heard from in 2012, so it's
fair to doubt that the code even compiles anymore on either one.
Remove both ports. We can always undo this if someone shows up
with an interest in maintaining and testing these platforms.
Discussion: <17177.1476136994@sss.pgh.pa.us>
I somehow had assumed that in the spinlock (in turn possibly using
semaphores) based fallback atomics implementation 32 bit writes could be
done without a lock. As far as the write goes that's correct, since
postgres supports only platforms with single-copy atomicity for aligned
32bit writes. But writing without holding the spinlock breaks
read-modify-write operations like pg_atomic_compare_exchange_u32(),
since they'll potentially "miss" a concurrent write, which can't happen
in actual hardware implementations.
In 9.6+ when using the fallback atomics implementation this could lead
to buffer header locks not being properly marked as released, and
potentially some related state corruption. I don't see a related danger
in 9.5 (earliest release with the API), because pg_atomic_write_u32()
wasn't used in a concurrent manner there.
The state variable of local buffers, before this change, were
manipulated using pg_atomic_write_u32(), to avoid unnecessary
synchronization overhead. As that'd not be the case anymore, introduce
and use pg_atomic_unlocked_write_u32(), which does not correctly
interact with RMW operations.
This bug only caused issues when postgres is compiled on platforms
without atomics support (i.e. no common new platform), or when compiled
with --disable-atomics, which explains why this wasn't noticed in
testing.
Reported-By: Tom Lane
Discussion: <14947.1475690465@sss.pgh.pa.us>
Backpatch: 9.5-, where the atomic operations API was introduced.
We weren't terribly consistent about whether to call Apple's OS "OS X"
or "Mac OS X", and the former is probably confusing to people who aren't
Apple users. Now that Apple has rebranded it "macOS", follow their lead
to establish a consistent naming pattern. Also, avoid the use of the
ancient project name "Darwin", except as the port code name which does not
seem desirable to change. (In short, this patch touches documentation and
comments, but no actual code.)
I didn't touch contrib/start-scripts/osx/, either. I suspect those are
obsolete and due for a rewrite, anyway.
I dithered about whether to apply this edit to old release notes, but
those were responsible for quite a lot of the inconsistencies, so I ended
up changing them too. Anyway, Apple's being ahistorical about this,
so why shouldn't we be?
Mostly these are just comments but there are a few in documentation
and a handful in code and tests. Hopefully this doesn't cause too much
unnecessary pain for backpatching. I relented from some of the most
common like "thru" for that reason. The rest don't seem numerous
enough to cause problems.
Thanks to Kevin Lyda's tool https://pypi.python.org/pypi/misspellings
Adjust the way we detect the locale. As a result the minumum Windows
version supported by VS2015 and later is Windows Vista. Add some tweaks
to remove new compiler warnings. Remove documentation references to the
now obsolete msysGit.
Michael Paquier, somewhat edited by me, reviewed by Christian Ullrich.
Backpatch to 9.5
pg_atomic_compare_exchange_*_impl() were providing only the semantics of
an acquire barrier. Buildfarm members hornet and mandrill revealed this
deficit beginning with commit 008608b9d5.
While we have no report of symptoms in 9.5, we can't rule out the
possibility of certain compilers, hardware, or extension code relying on
these functions' specified barrier semantics. Back-patch to 9.5, where
commit b64d92f1a5 introduced atomics.
Reviewed by Andres Freund.
The coverage was rather lean for cases that bind() or listen() might
return. Add entries for everything that there's a direct equivalent
for in the set of Unix errnos that elog.c has heard of.
There's no longer a need for the MSVC-version-specific code stanza that
forcibly redefines errno code symbols, because since commit 73838b52 we're
unconditionally redefining them in the stanza before this one anyway.
Now it's merely confusing and ugly, so get rid of it; and improve the
comment that explains what's going on here.
Although this is just cosmetic, back-patch anyway since I'm intending
to back-patch some less-cosmetic changes in this same hunk of code.
I've seen one too many "could not bind IPv4 socket: No error" log entries
from the Windows buildfarm members. Per previous discussion, this is
likely caused by the fact that we're doing nothing to translate
WSAGetLastError() to errno. Put in a wrapper layer to do that.
If this works as expected, it should get back-patched, but let's see what
happens in the buildfarm first.
Discussion: <4065.1452450340@sss.pgh.pa.us>
Architecture reference material specifies this order, and s_lock.h
inline assembly agrees. The former order failed to provide mutual
exclusion to lwlock.c and perhaps to other clients. The two xlc
buildfarm members, hornet and mandrill, have failed sixteen times with
duplicate key errors involving pg_class_oid_index or pg_type_oid_index.
Back-patch to 9.5, where commit b64d92f1a5
introduced atomics.
Reviewed by Andres Freund and Tom Lane.
Andrew Gierth
Tom Lane
Alvaro Herrera
Bruce Momjian
Heikki Linnakangas
Andres Freund
Magnus Hagander
Greg Stark
Andrew Dunstan
Noah Misch