Hi Anatol, all,
----- Original Message -----
From: "Anatol Belski"
Sent: Monday, November 16, 2015
Hi Matt,
-----Original Message-----
From: Matt Wilmas [mailto:php_li...@realplain.com]
Sent: Monday, November 16, 2015 2:59 PM
To: Anatol Belski <anatol....@belski.net>; internals@lists.php.net;
internals-
w...@lists.php.net
Cc: 'Dmitry Stogov' <dmi...@zend.com>; 'Pierre Joye'
<pierre....@gmail.com>
Subject: [INTERNALS-WIN] Re: [PHP-DEV] Windows (Visual Studio) compiler
stuff
> According to the docs __declspec(noinline) is specific to C++. Also
> with VS it's always much more tedious to inline something than the
> opposite. These are the main two reasons it's disregarded ATM. We can
> add it for compliance with C++, but it'll in best case have no effect
> in the PHP core. Should be tested before, though.
Yeah, I know what the docs imply ("member function"), which is why I
tested it.
I guess you missed my "works as expected" part. :-P
A test function that just returns a number was automatically inlined
(plain C).
Using __declspec(noinline) it was call'ed instead.
Not sure if any of the "zend_never_inline" PHP stuff is getting inlined
when it's
desired not to be -- I'll compile PHP in a bit and see what it looks like
with
"noinline."
Yeah, I knew it could work, just that it's undocumented so preferred not
even to start with it because I haven't expect much gain from it. The
functions I've seen with zend_never_inline are rather big and wouldn't get
inlined even when forced.
noinline did have an effect -- 12 KB smaller php7.dll. So, obviously it's
preventing those zend_never_inline functions from being inlined when they
currently are. Dmitry surely had reason to make them that way --
cache-related, I assume. Any difference, however "minor," is the same as
other compilers, so it's nice to know this can be used, with so many of the
other GCC/Clang "tricks" missing...
BTW, something "big" not getting inlined even when forced? I know the
"rules" about what can't be [force] inlined (basically same as GCC) and size
isn't one of them. :-) (I hope not.) As I've mentioned a bit, to be seen
soon, my "compile-time" param parsing optimization will have the "hugest"
inline function, but it compiles down to literally nothing, which I finally
got to work with MSVC as well. That's why I wasn't liking the idea of a
standalone copy of that stuff adding several KB to each module...
> I'd ask you for some concrete case for this, as I'm not sure to
> understand exactly what you mean. The only case where an extra code
> would be generated is with "__declspec(export) inline", but that's not
> the case anywhere within PHP.
My concrete case is checking tons of generated code! ;-)
It's simple: useless standalone functions are created for every "static
__forceinline" definition... Not having static makes it act like
GCC/Clang.
I guess I've understood what you're talking about - abut unreferenced
COMDATs (or maybe also duplicated COMDATs). There is a variety of
situations
for that, not possibly only inlining. Fixing it is done in PHP when
building
with --enable-debug-pack, that is on in release builds. In your
experiments,
if you add /Zi CFLAG (or explicitly /Gy) and /OPT:REF,ICF LDFLAG - that
will
solve it for yur other project. You can read more about COMDAT on MSDN.
Yeah, I know about the COMDAT stuff. And I thought I had tried the
/OPT:REF, etc. on a standalone test awhile ago and it didn't do anything...
I just now tried --enable-debug-pack, and as I was thinking, it had no
effect.
I don't need to solve anything on the other project since I didn't use
static there. :-P
Hm, probably these options could be revisited, as since 2013 there's also
/Gw and /Zc:inline switches which is not implied by /Zi. But have to do
more
checks, for now the release build options are good enough.
Again, I'll try to compile PHP with those static's removed and report the
effect
later.
Yes, thanks for your effort. I actually didn't check what gcc does for
such
cases, so curious. But "static" in "static inline" forces every
translation
unit to have even the same function to have different address, thus
eliminating the "one definition" rule for inline. We anyway need "static
inline" best compatibility, the compilers handle the rest :)
First, the report: Removing all the static's with zend_always_inline works
fine (since the __forceinline seems to "imply" static, no duplicate
symbols). It makes php7.dll 91 KB smaller (NTS --disable-all).
But then when I tried the /Zc:inline option (really sounds like C++ on MSDN)
the other day, I was pleasantly surprised! "You da man!" :-)
That saved over 220 KB, without removing static's. I verified that the
standalone functions (from static's) were gone, but obviously it also
removed a lot more. Thank you!
Hopefully that's a switch that can be taken advantage of?
Regards
Anatol
Thanks,
Matt
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