Re: [INTERNALS-WIN] Re: [PHP-DEV] Windows (Visual Studio) compiler stuff

Hi Anatol, all, ----- Original Message ----- From: "Anatol Belski" Sent: Monday, November 16, 2015

Hi Matt,

-----Original Message----- From: Matt Wilmas [mailto:php_lists@realplain.com] Sent: Monday, November 16, 2015 2:59 PM To: Anatol Belski <anatol.php@belski.net>; internals@lists.php.net;

internals-

win@lists.php.net Cc: 'Dmitry Stogov' <dmitry@zend.com>; 'Pierre Joye'

<pierre.php@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